Four power sources are practical for swaging, other than the strength of your arm: (1) Direct rotational electric power, (2) Inertial storage of rotational electric power, (3) Pneumatic pressure, and (4) Hydraulic pressure. The rest of this chapter is a discussion of the design considerations.

Direct Rotational Electric Power

Direct mechanical application of the torque from an electric motor's shaft can be used, through a system of gears or belts, for low power swaging systems. It is best suited for fully-automatic systems that would use small calibers (under .308-inch) and soft lead cores in thin jackets, or up to .357-inch bullets with soft lead and no jacket.

Building such a device usually means driving the ram of a press with a cam or eccentric bar, like a steam locomotive drive piston being turned by the wheels instead of the other way around. This lets the motor run constantly in one direction, avoids inertial stresses produced by stopping and reversing direction of gears, and produces a simple fixed stroke machine designed primarily for one bullet.

Practical size machines would use a motor of 1/2 to 1-1/2 horsepower, reducing the speed to gain torque by operating through gear trains or belts and sheaves. A ram speed of not over 2 inches per second is generally desirable. The reduction from a standard 1725 RPM single phase motor is a 28.75 to 1 ratio. The necessary ram force depends on caliber, material hardness, and shape of the die, but a 10,000 pound ram force is generally adequate for all lead bullets from .357 diameter down.

A drive wheel or gear with nominal circumference of 3.14 inches or diameter of two inches is just about as small as a wheel can be made and still wrap a practical size belt or accept the power from an adequate motor. So let's start with a motor shaft spinning a one inch radius (2-inch diameter) wheel (gear or sheave).

The two standard motor speeds are 3600 and 1725 RPM for single phase, 60-Hz. motors. The 1725 RPM motor will have greater torque for the same horsepower, since horsepower is simply torque times speed. That means our one inch radius wheel will be spinning at 1725 RPM. The circumference of the wheel is 3.14 inches. The number of inches of wheel that pass by a fixed spot in one second, then, is simply 3.14 inches times the velocity of 1725 complete turns per minute, divided by 60 (since there are 60 seconds in one minute).

This is 90.275 inches per second. That is the equivalent linear speed of the wheel, and it is much too fast for moving the swaging press ram. The inertial of the components would mean a very complex, powerful system of automatic handling would be required to get them in position and back out again before the ram struck, and the results would not be too good since the torque or thrust would be so small compared to the initial impact momentum. Lead needs time to flow.

Slowing the linear speed down without decreasing the horsepower would give us more torque, too. So let's turn a larger wheel, having more inches around its circumference. The ratio of the drive wheel circumference to the driven wheel will be the ratio of reduction in speed, since every inch of movement from the drive wheel transfers directly into an equal distance of movement on the circumference of the bigger wheel.

The distance that the ram must travel to swage a bullet has to be equal to the length of the bullet, plus a tiny amount of room for clearance so the bullet can fit easily in between the die opening and the ram, plus the amount of alignment distance required inside the die itself. Alignment distance must be at least the diameter of the bullet, and preferably twice that. This prevents galling and tipping of the precision punch that fits in the die behind the bullet. In a dedicated press that was designed only to make one kind of bullet, the stroke could be shortened so it came out according to this formula:

Stroke = 2C+1.1L

...where C = caliber and L = bullet length in inches.

With a typical .38 handgun bullet, the caliber is .3750 inches and the length is .70 inches. The stroke, by this minimum length formula, would be 1.484 inches. This means that on the output side of our system of wheels (gears, sheaves and belts), there will need to be a wheel with a pivot pin located 0.742 inches from the center of the shaft, and to this pin we shall attach a connecting rod to the bottom of our ram.

An alternative would be to make a cam by mounting the center of a wheel eccentric to the circumference, such that the difference between the lowest point and the highest point on the wheel relative to the shaft center was 1.484 inches. Either way achieves the same results. The cam requires a method of retracting the ram, such as a stout spring or a groove in the side of the wheel with a matching pin riding in it, the pin attached to the ram.

We know the stroke length and approximate desired speed of travel. At two inches per second, a ram moving 2.968 inches would make one complete stroke in 1.484 seconds (it must move up and back, total of 2.968 inches at a rate of 1 second for every two inches). This means the shaft turning the cam wheel must be rotating one complete turn in 1.484 seconds, since each turn is a complete stroke.

Now we know the rotational speed required for the driven wheel: it is 1 revolution per 1.484 seconds, which is the same as .67385445 turns per second, or 40.431 turns per minute. The reduction ratio from input to output of our wheel system must take the 1725 RPM of the motor down to 40.431 RPM for the cam wheel that drives the ram. This is a ratio of 1725 divided by 40.431, or 42.665 to 1.

If you think about it, you will see why mechanical rotation is not usually practical as a power source on anything but small systems requiring small ram forces. The cost of the gears and wheels, and the power loss through the system of belts, would be unacceptable.

The ratio of circumferences is in direct proportion to the speed ratio, while the ratio of diameters is a square root proportion. With a drive wheel of 2-inch diameter (1-inch radius), and circumference of 3.14 inches, the circumference of the driven wheel or cam in a single reduction system would have to be 133.97 inches! The diameter of this huge cam driver would be 42.64 inches, or about 3.55 feet!

Of course, with a train of gears, this could be handled nicely in a smaller package, but it would be expensive. Using a worm gear drive is the most practical method of reducing the speed. The friction caused by the high ratio worm gear reduces power considerably.

In a clock, high ratio reduction systems are practical because the total torque transfer is small. The gears can be tiny, fragile things that pack tightly into a small space. In a machine like this, the torque transfer is large. The gears must be beefy to handle it. Being strong and also having a high reduction ratio means they are going to be large and costly. It also means there will be quite a bit of power loss.

A power reloading press can utilize a cam or worm-gear drive system without undue cost because the required power is quite low compared to swaging. The amount of pressure required to size a case or seat a bullet is a fraction of the amount used to cold-flow metal into the shape of a bullet.

People who have not done the math or tried building swaging systems before often wonder why there are no multi-position swaging presses, either hand or power. Not only would the different steps of swaging a bullet require different amounts of pressure and insertion depth, but applying all of them in a three to six stage bullet-forming operation would mean building a huge power system to run it.

Inertial Storage of Rotational Electric Power

For most applications involving direct mechanical force, the energy is first stored in a heavy mass, by spinning a flywheel. As the speed of the flywheel builds up, it stores more energy. When it reaches designed speed, a trip is engaged to catch a tooth or gear on the moving flywheel and transfer its energy to a ram.

This system allows the motor to supply energy over a longer period of time than just one stroke. The motor can feed energy into the flywheel while components are being moved under the die, ejected, and during the return stroke. Typically, this kind of system only has full power at the bottom of the stroke (assuming the ram is on top, as with most punch presses). The cam or connecting-rod mechanism also develops its full power (minimum speed, maximum force) at the ends of the stroke.

This is an important concept to understand. The swaging process normally requires very little force while the component is moving into the die. Most of the ram force is required at the end of the stroke, when the components have stopped moving and are being expanded under high pressure. So, for swaging operations, the mechanical system seems to be ideal.

But when you include jacket forming, drawing, and other operations that utilize a great deal of force right from the entry of the component into the die, these systems fail to deliver the necessary energy in the right form until the press reaches massive size compared to air or oil pressure presses. The typical size of press required for single station bullet swaging needs at least a ram travel twice the length of the bullet, and a tonnage rating of between ten and twenty five tons.

The tonnage of a punch press is not quite the same thing as the actual ram force of a fluid power system, because the tonnage is only generated in full when the press has extended its stroke all the way.The ram is attached through a crankshaft or toggle in the typical punch press design. The energy stored in the spinning flywheel is applied to the crankshaft while the ram is at the top position, and the leverage that multiplies the force depends on the angle of the connecting rod.

The force available to flow the bullet materials when the ram is starting down, or when it is half an inch above the full stroke length, is considerably less than rated tonnage. It is necessary to purchase a much larger tonnage press in order to have the desired ram thrust available higher in the stroke.

Punch presses, eyelet presses, transfer presses, and other variations on the flywheel press are often used to punch and form sheet metal. With fraction of an inch thicknesses, the rated tonnage is close to being the amount available to punch, shear, and bend the workpiece. But when long tubular parts are being formed, or when deep drawing cylinders like bullet jackets, full force may be required much higher in the stroke.

Inertial presses of twenty to fifty tons rated force are typically used for high volume production. The presses themselves generally are in the middle five to low six figure price range, new, without tooling. They require a fairly large operating area with moderately high ceiling, and generally use commercial three-phase power motors. The basic open back, inclined bed punch press can be used with a stack of dies, to make several drawing reductions in one pass.

OBI presses are usually the least costly design and are available in small tonnage sizes. I once used a little two-ton OBI press that I bought at a surplus machinery sale and carried to the trunk of my 240z sports car, then drove home with it comfortably resting on my overnight bag! It was far too small for bullet making but punched nice hole patterns in the cover for an electronic device that I was manufacturing. It was almost worth designing products just to see the little fellow punch the parts.

Eyelet presses are a kind of "dial feed" single station press. They use a rotary feed mechanism that positions the part under the ram, and moves it around to eject and load more parts. Transfer presses are usually multi-station, which means that the ram is attached to a number of punches or die shoe assemblies, all in a row. The workpiece, which is normally a continuous strip of metal, is fed into the first station, and is advanced by a clever "shuttle feed" device from one position to the next.

The strip is fed into the first station with a strip feeder, which can use friction rollers or one-way spring-loaded gates that push the strip one direction but slide over the strip on the back stroke. Or air clamp cylinders can be used to grasp and move the strip forward. At the first station, the strip is cut or punched to make a "coin", for deep drawing operations. The coin may be left attached by thin flanges to the strip, so that the strip can be used to advance the part, or it may be cut free from the strip.

The shuttle feed is made as two halves of a multiple part clamp, which spread apart (open), move backward one position, close together (clamp), and then move forward one position. This motion is repeated over and over again, and has the effect of grasping a part, moving it to the next station, releasing it over the die hole, and moving back to get the next part.

I mentioned "die shoes" without explaining them. These are standard methods of holding and aligning the punches and dies so that they remain in alignment when you remove them from the press. The typical die shoe consists of a base plate, two or more hardened and ground support rods which are fitted with bearings within a sliding plate.

The base and sliding plate chomp up and down, powered by the press ram and supported within the opening of the press by being bolted or clamped in place. You can usually change the actual dies and punches fairly easily in the die shoe, which is a sort of intermediate mechanism between the press and the dies, providing the precision alignment instead of the press having to be built with high accuracy components to hold the dies and punches. .Die shoes are available in different configurations and sizes as more or less standard items, separate from the custom dies themselves.

In the Corbin swaging presses, we eliminate the die shoe and build the precision into the press head itself, and then standardize the dimensions of the dies and punches as far as their methods of holding and alignmenet, retaining the custom dimensions for the actual parts. We can do that, saving you thousands of dollars over the typical punch press system, because we are limiting the kind of products formed to a fairly small range of lengths and diameters in tubular forms (jackets and bullets, not car fenders, napkin holders and flashlight cases). The die shoe is a design feature that helps the punch press handle an extreme range of product sizes and shapes compared to the bullet and jacket making field, something you don't need if the press itself is designed for that field.

As you can see, the punch press is extremely versatile and can be used for anything from automobile fenders to flashlight cases. But the various complex feed devices and the die and punch sets themselves are not flexible. They are made to do one specific part, of one size, material, weight, shape... and they are very expensive because they must be built specifically for you, for each part you want to make.

When it comes to bullet swaging, a person wanting to use high speed punch presses will need to buy the press (a used one in the ten to fifty thousand dollar range would be about average investment) and then find a die designer to work out the blueprints and specifications for feeds and dies for the specific press to make your parts.

Once the tooling engineer has worked out the design, you need to take it to a tool and die shop and have them actually construct the tooling. Some of it will be universal, off-the-shelf component modules, and some of it will be built to blueprints. Once the tooling has been constructed according to your blueprints, you then need to get an experienced punch press set-up person to put it all together and debug it, because no one involved in the process is responsible for final operation except you.

If the material tears or punches through instead of drawing, or if the parts stick on the punches, the tool and die shop will only be responsible for having made the parts to the tolerances specified on the blueprint. The tooling engineer will only be responsible for his design and not for the implementation of it, so that if any parts are not made correctly he is not going to take responsibility. And if you use a material with a different temper, tolerances, or grain structure than was specified, no one is resonsible for it working butyou.

Once when I was backlogged two and three years with jobs and simply didn't have enough available time to design my own jacket drawing dies for a high production press, I hired a firm who said they had deep drawing experience to both design some new jacket-drawing tools and build them. That way, the opportunity for finger-pointing was reduced since one firm would be responsible for both design and construction. But after four months and a few thousand dollars spent on "progress payments", the company gave up. They could not make the punch press form soft copper into jackets. Did I get my money back? Are you kidding?

What I got was what you or anyone else would get: a box full of parts including the die shoes and dies, a bill marked paid, and a suggestion to use some other material. That's just how it is with the tool and die business. You pay for people to try and you take your chances unless you know for certain that you already have a design with the correct tolerances and dimensions, and that if someone follows your plan exactly in making the tools, they will work.

If you leave it up to someone else to design your tooling, you might possibly have some recourse if in the end it doesn't work, but the odds are very good that one of about a hundred different escape clauses will leave you stuck with the bill and useless tools. The reason is that if you don't know enough about it to design the blueprints yourself, you probably don't know enough about the materials and setup to guarantee that you follow precisely what the designer intended. He might be able to make it work if he were the one who built the dies and set it all up, bought the material and ran the press. But of course, he doesn't do most of that. Someone else does. So at every step of the way, there is finger-pointing. It is always someone else's fault.

A few years later, when I had more time and some good die-makers working for me, we built tooling that drew pure copper strip into excellent bullet jackets. It took many years and tens of thousands of dollars to evolve to the level we have today. And the process has never stopped. I have no doubt that in five years, we'll be making tools that are faster and better still. Actually, the next set we make will have improvements that we didn't even consider necessary or possible yesterday. And our clients get the benefit of each thing we learn. Also, we are responsible for the design and the construction, and all the client has to accept is responsibility for using the right material and following our instructions (in order to get warranty service for any failure to produce the part specified).

Naturally, anyone can interfere with the operation of a precision process by failing to use the right material, or by using it incorrectly. But your level of responsibility is orders of magnitude less, when you buy a "turn-key" package designed around a specific material and guaranteed to make a certain part to specific tolerances.

You can't buy different material and expect it to always produce the same results as the material used to design the tools, nor can you decide to skip some steps or make changes in the lubrication, speed of operation, or physical parameters of the material and then hold the die-makers responsible if it doesn't work the same as it did with the right material and procedure. But that is a far cry from the risk you incur with tooling up a typical transfer press.

Because the tooling for inertial presses is designed around the handling between operations, most of the cost is in fact in the feeding of the parts rather than in the press or the forming dies themselves. It is hard to separate the feeding and forming costs, though, because the dies incorporate some of the feed system in most cases. As a general rule, the requirement for high volume, high speed operation is primarily a requirement for dedicated feeding systems for each part. The press and dies is slave to the feeding method that advances the parts through the process without human intervention.

The human hand is extremely versatile, and most people get two of them free, the ultimate robotic feed system in regard to instantly switching from one part size to another. True, it is slow. That is fine, in a market where 150,000 parts per year would be saturation, and the customers are willing to pay from fifty cents to as much as two dollars a bullet. The bulk of the gross profit goes to pay for your time, rather than going to pay for debt service on expensive machinery.

That is why the most versatile kind of press, requiring the least investment and size for the most versatility and capacity, is a fluid power press.

Pneumatic Pressure

The lowest-cost fluid power system is compressed air. The field of fluid power transmission includes both air and hydraulics. Both gas and liquid are considered "fluids" in this application.

Air, being composed of gasses (primarily nitrogen), behaves according to conventional physics rules for gas. That is, it takes up less volume and becomes more dense as pressure is increased, and it expands in volume or increases in pressure as temperature rises. Liquids are relatively incompressible compared to gasses, so they behave differently under pressure.

An air compressor might typically be capable of developing from 90 to 150 pounds per square inch of compressed air pressure. Since the typical internal die pressure required to form soft lead properly into a bullet shape, regardless of caliber, is about 15,000 to 20,000 psi (depending on die shape), a 4-inch diameter air cylinder would just barely have enough area to produce the force to swage a soft lead .357 caliber bullet, driven from a normal air compressor.

On the other hand, air pressure of only 90-100 psi on a 4-inch drive cylinder allows enough ram force to swage .224 and .243 rifle bullets very nicely. A pressure of 28,699 psi can be developed in a .224 inch die at just 90 psi of air pressure, using the 4-inch cylinder.

An air-driven swage press is practical for small calibers. It is possible to build a practical press to swage .308 rifle bullets, using only 125 psi air pressure, and a six-inch diameter drive cylinder. The internal die pressure can reach 37,949 psi with such a combination.

How much pressure is required? That depends on the jacket material, thickness, and core hardness as well as the bullet shape. It can range from a low of about 10,000 psi for soft lead with simple, easily formed ends to a high of more than 150,000 psi for heavy jacketed bullet brought to small tips. Our range of internal die pressures, practically speaking, spans a 15:1 ratio.

Internal die pressure is related to the square of the caliber, since the caliber is the diameter of the piston or punch that applies pressure to the material in the die. It is directly related to ram force. Thus, the ram force range has a 15:1 ratio for practical bullet forming operations. Ram force is in squared ratio to the drive cylinder diameter, but again in direct ratio to the drive pressure applied to the fluid or air in the drive cylinder.

With air equipment that is practical for non-laboratory use, the largest bullet than can be formed with certainty is a .308 caliber having a conventional thin jacket, no boattail, and fairly standard 6-S ogive. A soft lead .357 bullet can be formed with certainty in nearly all but the most complex nose and base shapes. Anything larger or more pointed, or having material any harder than soft lead for the core, is very likely NOT to form properly.

A cylinder larger than six inch diameter is not only very expensive but tends to introduce other problems, such as speed of actuation, oscillation in the system, requirements for excessive-sized feed lines to exhaust the cylinder, and multifarious conundrums beyond the scope of this discussion. The only other alternative is higher air pressure, and that is limited by the cost and availability of regulators, fittings, filters, and other appliances to control the system, not to mention the compressor itself.

Corbin built air presses for a number of years. They were marginally effective compared to hydraulic systems, but the demand was great enough to justify developing them. Cost on a 4-inch bore system is reasonable and if the bullet maker understands the limitations, and accepts them, then making .22 jackets from fired .22 cases and forming .224 to .357 bullets of certain types from soft lead can be done very nicely.

The air-over-oil system is a hybrid design wherein air pressure is applied to one side of a hydraulic cylinder, and the other side is filled with oil. This helps to eliminate some of the problems with pneumatic systems in regard to the "spring" or compressibility of air. It does not change the forces and pressures possible, but merely adds some additional control.

One of the problems with air systems is the instant action you get when you apply compressed air to the cylinder. It is restricted only by inertia and friction, which isn't a lot of restriction, so it flys forward and back with virtually impact forces, a little bit like a punch press. The speed doesn't really allow time for some materials to flow. It rips and tears the ends off bullet jackets, for example, and can generate rather excessive shock waves that crack swaging dies because the material acts as if it is much harder when you don't give it time to flow from a freshly applied force.

The air-over-oil hybrid system gives more control over speed, since you can more easily meter the oil flow through a restrictor valve (speed control) than you can with air flow. Air speed controls are available but they are not usually as precise, reliable, and wide-ranging in their flow ratio adjustment.

When you are swaging a lead core, there is normally a physical stop set up so that you don't continue to extrude lead until the entire core is gone. With core seating and point forming, sometimes a person wishes to use a certain pressure level as the sensing point to stop pressing. With hydraulics, the pressure is reached and the material is compressed in the die very uniformly. The ram can be stopped almost instantly by switching a valve, run by a pressure transducer.

With air, you can shut off the valve and yet the ram will continue to move for a noticable time. Inertia and expansion within the system can cause problems on larger systems with movement when it should not be taking place. This is because air does compress, and shock waves can travel through it, causing movements after a valve is closed.

With hydraulics, the material transfers pressure instantly (or nearly so) throughout the entire system. The application or removal of pressure at one point has an almost immediate effect on the entire system. Movement is much more precisely limited by controlling the pressure. For bullet swaging, hydraulic power presses offer significant advantage over air presses.

The main physical difference between air and oil systems is the compressibility of the fluid: air is highly compressible, hydraulic fluid is almost incompressible. Hydraulic systems act more like flexible metal shafts, so that a shove on one end almost instantly transfers power at the other end. Air acts more like a big spring, where a push on one end eventually travels through the spring as it collapses in relation to the force.

Hydraulic pressure.

Hydraulics originally meant water power. A hydraulic-electric generator is a water-powered turbine. But in the fluid power field, it has come to mean oil or synthetic oil under pressure. Hydraulic fluid can be a water-based synthetic material or a light oil.

The oil is not designed for lubrication, but has low foaming when splashed around, low capacity to adsorb air and gasses under pressure, and is highly incompressible. It is made to maintain viscosity under high temperature and to transfer heat as well as possible. Certain pump and valve components are designed using materials that are compatible with either distilled petroleum or synthetic based hydraulic fluids. The solvent action of some fluids will destroy these components, so it is important to use the recommended hydraulic fluid.

Never mix types of hydraulic fluids unless the manufacturer of each fluid agrees that they are compatible. Never replace hydraulic fluid with motor oil or brake fluid. Just because it says "oil" doesn't mean you can use it on your salad, or in a precision press.

Another reason for using the correct fluid is that the pump is rated to handle a certain load, in a certain temperature range, with a specified viscocity or flow resistance of oil. If the fluid does not match this pressure and temperature range, it will break down and leak past the pump vanes. The pump will cavitate, the oil will further heat, and the pump seals can be destroyed. Further heating can cause pump seizure, destroying the rotor or the housing.

This is mentioned at the outset because it is important to use the correct fluid in a hydraulic system, and there seems to be quite a bit of confusion over what hydraulic fluid is. There are many grades and formulations, and quite a few are incompatible with each other and with the pump and valve components of some systems.

The hydraulic fluid used in Corbin presses at this writing is Chevron AW-46, which has cross-referenced equivalent numbers to other brands and is commonly available from hydraulic component suppliers, and from commercial oil distributors. This is an anti-foaming fluid that reduces cavitation and is usable over a fairly large range of temperatures. Extreme cold is not a suitable environment for operation.

The room in which the press is stored and used should be kept in the normal comfort range for human habitation (from 65 to 85 degrees F, preferably closer to 70 degrees F.). The viscosity of the hydraulic fluid increases with lowered temperature, so that operating the press or even starting the motor in a cold environment can draw too much current and blow a fuse or trip the 20 ampere circuit breaker/power switch.

If it is necessary to store the press at lower temperatures, the room should be slowly warmed to the proper operating temperature so that condensation is avoided. Once we received a Hydro-press for repairs, and every exposed steel component was coated with a layer of red rust. The press had been stored in an unheated shed, which was warmed up whenever the weather changed or the owner fired up a wood stove in preparation for making a few bullets. Moisture condensed on the precision steel components, which the owner failed to lubricate. The repairs consequently included replacing parts that would have been perfectly fine for several lifetimes if the room had just been warmed up slowly and a little rust-preventive oil wiped onto the exposed metal.

At such times, the old expression "casting pearls before the swine" comes to mind, in the sense that a person who cares enough to research and buy the finest machine of its kind, a machine with decades of research and development behind it, built by a die-works with a hard-earned, world-wide reputation for careful design and construction, should at least care enough about their investment to try to take the most basic care of the machine. Not that I'd ever compare a client to a pig, of course.

It's their money and none of my business once they take posession. I'm sure the people who design target pistols would have choice names for me if they saw how selcom their fine products are cleaned after a match (especially the 22's which get cleaned so infrequently that they might indeed bring a pig's sty to mind). A family friend has an interesting turn of phrase, a result of not hearing the term correctly and then continuing to mis-pronounce it until it became ingrained habit: the phrase is "pig stein", which always brings to mind a "hogshead" of beer for some reason. The pistols continue to work fine, though, even the one's I've used for forty years, and I do wipe them with oiled cloth now and again.

Still, lack of care seems like such a waste, especially when it takes so little to maintain the machine virtually forever. Some of the earliest Hydro-presses are now going on 30 years of service, having made millions of bullets. Some of them have never had the oil changed, and the only components replaced have been indicator bulbs on the control panel. I recommend changing the oil and the filter once after about 2000 hours of operation, but apparently this is precautionary rather than a necessity. The system is closed, there are no combustion products to contaminate the oil, and the only reason for deterioration is the fine particle accumulation that takes place from normal wearing of the pump rotor vanes (which the filter should trap).

Hydraulics have significant advantages over other drive types. A compact power system can deliver extreme pressures at moderate speeds. Control can be precise and easily adjusted with electronic sensors and logic. This opens the door to automatic control over system variables such as pressure, timing, speed and position.

The skill required to produce good bullets on a hand press includes the ability to sense a consistent pressure level by feel of the handle and ram resistance, and the sense of timing necessary to hold the ram forward the same time on each stroke. The electronics of a properly-designed hydraulic system can eliminate the need for this skill, and maintain consistency far beyond that possible by manual methods.

Hydraulic power by itself is not the answer to successful bullet production. Merely connecting a pump to a cylinder and slamming it back and forth in a mindless display of raw force will NOT make good bullets, and it probably will break dies and possibly injure the operator.

Control over the force, in the form of a logic and sensing system that is able to detect smaller variations than a person could possibly notice, and to act on them with greater speed than is possible by hand, repeating the expert performance reliably no matter how long the production run — that is the secret of making good bullets by hydraulic power.

The electronic system does not replace the operator, but extends his ability by doing his will more quickly and more precisely. It is not a "robot" that replaces the skilled hands, but a tool placed in those hands — a tool vastly more sensitive and at the same time more powerful than anything else available, but still under the control of the operator, and depending on his knowledge or on the knowledge of the person who set up the press. Once the knowledge has been applied, and the system is set up to make a perfect bullet of a given weight and shape, then the system can continue to repeat that performance regardless of who comes along to drop the parts into the die and press the buttons.

The bullet maker can walk along a row of such machines, setting each one up to do his bidding, check and adjust them to obtain the results he desires, and then put someone to work dropping parts into the die and pressing the buttons for the rest of the week.

This is the great advantage of such a system. Not only is it more powerful, for less cost, than anything else available, but it is capable of duplicating the skill of the bullet-maker, giving anyone the ability to produce a high quality bullet. At that point, it does become a replacement for skilled hands—but only after receiving "orders" from the higher authority of the bullet maker.

The hydraulic system can apply the same force at the bottom, middle, and top of the stroke. It does not have a limit on where the ram must be to develop maximum power. This means that operations such as jacket forming and bullet reduction are much easier. It means that lead wire extrusion is practical.

Practical hydraulic components of industrial quality (not farm or automotive components, which are built with dirty working environments as a main concern, and have lifespans more suitable for the average auto or combined growing seasons than industrial hydraulics) can be obtained with reasonable pricing with a maximum working pressure of 2000 psi (shock-rated) and 5000 psi static pressure (non-shock). The design of Corbin systems take advantage of the cost curve and use a 2000 psi pump so that components can be readily matched.

Higher pressures put the controls in a higher price category, while lower pressures reduce the range of functions or require much larger diameter drive cylinders and thus increase the cost of the system out of proportion to the benefits. Pressure also has a relationship to the kind of hydraulic lines used to plumb the press. Higher pressure on flexible hydraulic hoses places more torque or bending force on the connections and components except for straight-line connections, and is more likely to cause seepage or leaks. The entire system, including the weight and thickness of the cabinet and frame, is designed to match the pressure, bending movement of lines, and ultimately the horsepower of the drive motor.

Rigid steel line costs less than flexible hose, but it is more difficult to fit and replace. It is subject to fracture at the flared fittings from vibration or repeated stress, which causes seepage of oil. Vibration and shipping stresses, such as sudden stops and accelerations, can shake heavy components or flex the cabinet slightly, and loosen or crack the connections made with solid steel tubing.

Replacement of steel tubing requires either precisely pre-formed bends and lengths of exactness that may not be practical, or the custom-fitting of tubing by the installer using tubing benders, cutters, flaring tools and wrenches.

Flexible hydraulic tubing uses more expensive fittings and is itself considerably more costly than steel line, but if properly sized with generous loops, it can better handle mechanical stress and can also be replaced with nothing more than an open-end wrench. The design of the cabinet, routing of the hoses, and mounting of components becomes more critical with flexible tubing, since the oil pressure will try to "uncoil" loops or straighten U-bends. The force can be enough to break mounting bolts, bend or break housings and unscrew the connectors if the effects of hose torque are not taken into consideration. In some cases it may be necessary to secure the loops by mounting to solid structural supports so that the torque is not so great on the fittings.

Ram thrust, drive pressure, and internal die pressure are related but not the same thing. It is important to understand the differences. With a range of from 100 psi to 2000 psi on the gage (drive pressure), a cylinder of 3.25-inch diameter can produce a ram thrust of 829.58 to 16,591.54 pounds. This thrust is independent of caliber, depending only on the applied pressure and cylinder diameter. At 2000 psi on the gage, the press is developing a thrust of 8.3 tons.

This thrust, however, must be channeled through the face of a punch to apply pressure within the die. To transform the ram thrust into die pressure, we must know the caliber (diameter) of the punch. The formula, written using computer math notation, is...

P_d = F/A_d

...in English, this means divide the force of the ram, in pounds (F), by the Area of the punch tip in square inches (A_d). Die pressure (P_d) is in pounds per square inch. The area of the punch tip is given by the formula...

A_d = Pi * C² / 4

...where Pi is 3.14159.... (number of times the diameter of a circle will go into its circumference), and C is the caliber or diameter of the punch. You could replace C²/4 with half the caliber, or radius, squared, since the area of a circle is also Pi * r².

As the diameter of the bullet gets smaller, the pressure that is produced in the die with the same ram thrust goes up very quickly (in proportion to the squared caliber). Smaller calibers, then, require far less ram thrust than larger ones to develop enough pressure so that the lead flows and the bullet forms correctly. Lead flows at a certain pressure, depending on temperature and exact alloy composition, that is usually about 15,000 psi in a smooth-sided cylindrical die. It takes about 20,000 psi to form a good replica of the inside of the die using a normal jacket over the lead.

This is not related to caliber, drive cylinder size, or oil pressure. In other words, soft lead at normal room temperature will flow well enough for swaging at 15,000 psi no matter what the caliber. This is internal pressure on the lead, within the die. The force that it takes to generate that pressure is very much dependent on the diameter of the die. This is why you can easily swage a jacketed bullet in a small reloading press, in .224 caliber, but increasing it to .458 caliber requires vastly more effort and might over-stress the components of typical reloading presses.

The figure of 15,000 psi is a bit arbitrary. Lead starts to flow under very small stress, even at 1000 psi. There are instances where tall buildings have been built with pads of lead sheet between the concrete foundation pilings and the support columns, as a way to spread the force evenly and allow for some expansion movement. After years of being under pressure, the lead was found to be slowly extruding, with a creep rate of a few thousandths of an inch per year!

The rate of lead flow under lower pressures is extremely slow. As pressure is increased, the speed of movement goes up. The range of 15,000 to 20,000 psi is a high enough estimate so that soft lead cores inside a normal gilding metal jacket of 0.015 to 0.027 inch wall thickness will form completely in standard bullet dies, within half a second or less. This is long enough to get the job done at a reasonable pressure without excessive concious effort to maintain a specific dwell time with hand press operation. (With a power press, the dwell time can be precisely dialed up and repeated automatically.)

The pressure within the hydraulic system that is necessary to form a bullet depends on both the caliber and the size of the drive cylinder. We've just shown how to calculate ram force from required die pressure and caliber. Now, here is how to calculate the oil pressure necessary to develop any given ram force...

P_s = F/A_s

...which means, the hydraulic system pressure (P_s) equals the ram force (F) divided by the area of the system drive cylinder (A_s).

The area of the cylinder, A_s, is equal to the square of its diameter times Pi (3.14159) divided by 4. This is the same formula as the area of the punch tip. We can put this all into one formula by saying that the gage pressure is equal to the die pressure times the square of the die diameter, divided by the square of the drive cylinder diameter...

P_s = P_d * C² / D²

In the case of the Corbin Hydro-press with its 3.25" drive cylinder, the formula is...

P_s = P_d * C² / 10.5625

Conversely, to find out what pressure you would apply to any given size of bullet swage die, multiply the gage pressure times the square of the diameter of the drive cylinder, and divide that by the square of the diameter of the swage die bore (or punch tip).

The formula for die pressure is...

P_d = P_s * D² / C²

This brings up one other minor problem: how much pressure can you apply before the die breaks? And, how do you know before it happens so you can avoid it?

With a hand press, there is almost no good way to tell. You must learn by "feel" and approach maximum pressures with caution, just as you do in reloading. In the Corbin Hydro-press, a gage reads system pressure directly in PSI. You can easily look up the caliber (or diameter of die) in the tables provided in this book, then read the maximum allowable pressure for a standard Hydro-press die. Set the automatic pressure reverse or the pressure limit for that pressure or slightly less, operate with the suggested approach speed to avoid excess shock, and you will not break your die.

The amount of pressure needed will be considerably less, usually, than the breaking pressure. If you reach the breaking pressure, and the bullet still has not formed up correctly, then the job cannot be done using that particular material in that die. It is up to you to quit at that point. Check the tables. Thousands of dollars worth of tests and piles of broken dies have been created to test the tables in this book. If you continue, you will probably break the die. That may provide full employment for our die-makers, but it does your bottom line no good at all. I recommend against it (counter to the advice of our accountants, who think it would be a capital idea). What if the job cannot be done with a standard die? Must you give up?

No, there are three more choices. You can change materials so that you find a material that flows more readily. Usually the material you are using is too hard and won't flow readily. Or, you can drill a hole in the end of the metal slug, so that there is a relief for the compression of the metal. Drilling over half-way through a piece of brass rod with a 1/8-inch drill will remove enough of the center so that you can form a solid brass .50 caliber machine gun bullet in one stroke from a half-inch diameter rod.

Or, you can order a special die. Corbin can make them in a larger diameter than standard for special applications. The limit of special die diameters is reached when you need over 200,000 psi.

It should not be necessary for you to need this much pressure. But that is the limit regardless of die size since it is the tensile strength of the strongest alloy we use, less about 50,000 psi for safety margin. The standard die for the Hydro-press is 1.5-inch diameter. Increasing the diameter to two inches will increase the allowable strength several tons on a big bore, but hardly make any difference on a small bore. The formula for die strength is given in the next chapter.

The design of the Hydro-press is such that the die fits into the ram. The ram moves vertically. You are thus able to drop your bullet into the die. The internal punch fits down into the ram, and pushes the bullet back out of the die on the bottom of the stroke. Then, the ram can be set to move up a short distance so the internal punch is retracted slightly. This opens up the die, so to speak, so that you can drop the bullet in and not have to hold it when the press is running.

All Corbin presses have vertical rams with the die fitted to the ram. Two manual models and three hydraulic models are produced at this writing. Although most of the discussion here is directed to the Hydro-press, please bear in mind that in some situations you may be nearly as well served by one of the smaller hydraulic or even manual systems.

Any power press should have a means for alignment of the bullet and punches in the die that does NOT require the operator to hold the bullet or the punch. In the Hydro-press, two buttons are provided as a safety measure. They are located on the front top panel so you can easily press one with the right hand, and one with the left hand.

At no time should it be necessary to reach into the area of the moving ram, but if you DO lift your hand from either button, the ram will stop.

Sometimes, it is more convenient to let the ram continue to move up and down while parts are put into and taken out of the ram. An example would be sizing a long run of cases, using the reloading adapter and shell holder. Because we are adults and responsible for our actions, there is a key switch on the Hydro-press that allows the operator to select automatic operation. When the key is put in this position, a red light comes on as a warning.

Pressing the right button (UP), holding it down and then pressing the left button (ENERGIZE), is half the sequence that sets up automatic ram operation. If you lift your hand off the left (ENERGIZE) button first, and then release the right (UP) button, the sequence of events finishes programming the logic for automatic ram movement. The ram continues to move with both buttons released.

The left (ENERGIZE) button is then programmed to act as an emergency stop, and the yellow DOWN button is set to over-ride all other functions except emergency stop. Press and release the ENERGIZE button to stop the ram. Press the yellow DOWN button to reverse it, but be aware it will go up again by itself when you release the DOWN button.

The automatic sequence should only be used by an adult who is alert and willing to pay careful attention to what he is doing. Any press as powerful as the Hydro-press can cause serious injury to the hands. The key can be removed in the manual position to prevent anyone from ever using the automatic function. The motor (pump) switch still controls the system and can shut it off.

It is encouraging to note that there has never been a reported injury using the Hydro-press. The speed of ram travel, clearance between steel support plates, and design of the control system all contribute to a safe operation, even with pressures of two thousand atmospheres routinely generated!

The pressure necessary within a swaging die is determined by core hardness, jacket hardness, and the resistance generated by the shape of the die and punch faces. To some extent it is affected by die finish, although a die must be extremely well finished to work at all.

Pressures generated in any given die are limited by the tensile strength of the die material, die wall thickness, and thus by both die diameter and bullet diameter. Since dies are generally short compared to their diameter, the length of the die has no significant effect on die strength.

Typical pressures to form pure lead bullets range from a low of 10,000 psi to a high of 22,000 psi. An alloy of 2% antimony with lead, which increases the hardness from Bh 5 to about Bh 8, can easily double the required pressure to as much as 45,000 psi.

It is very important to understand the difference between internal die pressure, which has meaning independent of the system in which it is used and remains fixed for the performance of a given job, and the ram thrust and system pressure. These latter two measurements mean nothing without reference to a given drive cylinder diameter and a given caliber of die.

When someone asks, "How much pressure does it produce?", I always wonder if they'll understand the significance of the answer. Any given design of bullet will require exactly the same pressure to produce, whether it is made on a hand press or a Hydro-press.

The press will only produce as much pressure as the resistance provides. No matter if the gage could be made to read hundreds of tons of pressure, the hydraulic system merely responds to resistance. If it meets no resistance, it produces no pressure.

When you put lead in a die, and the die has bleed holes to let you extrude some of the surplus lead, the pressure will only rise until the resistance from the flow of lead through those holes matches the ram thrust. Moving the ram faster increases the pressure only because greater resistance to the flow occurs at higher velocity. If you set the press for a limit of only 500 psi on the gage, then it will never produce more than 500 psi within the system itself.

But, if this same 500 psi that always produces 4,147.88 pounds of ram thrust in the Corbin Hydro-press is generated in some other system, it could produce any ram thrust the builder desired. Whatever size drive cylinder is used will determine whether that is a puny pressure or a dangerous one.

For instance, 500 psi with a 4-inch cylinder produces 6,280 pounds of thrust. With a 6-inch cylinder, that translates to 14,130 pounds. And with a 12-inch cylinder, it creates 56,520 pounds — over 28 tons!

So, for someone to ask how much pressure the press produces is rather interesting. Unless they know the drive cylinder diameter and the diameter of the swage die, any number is as good as another! The press can produce whatever pressure you want, given the right size of die and drive cylinder. The drive cylinder diameter of the Hydro-press is 3.25 inches. This corresponds to an area of 8.29577 square inches. Force is equal to pressure times area.

But the ram thrust or press tonnage is not very useful information unless you relate it to a die bore size. The same force that produces 35,703 psi inside a .172 caliber die would barely register 4,029 psi in a .50 machine gun die (.512"). That pressure, in the Hydro-press, is produced by a mere 100 psi on the gage.

The amount of pressure the press can produce in a die depends on the bore size of the die. The smaller the bore size, the higher the pressure it can produce. There is an interesting correspondence between the rapid rise in pressure that the same ram thrust produces in smaller bores, and the increase in die strength as you make the hole smaller. The die strength goes up, too. But it doesn't go up nearly as fast.

For instance, that .172 die in a standard 1.5-inch Hydro-press design can hold 185,905 psi internal pressure. The .512 die can hold 102,198 psi before it breaks. Yet, in order to break the .172 die, all you have to see on the system gage is a mere 520.7 psi. To break the .512 die, you would need to generate a system pressure of 2,536 psi (beyond the normal system capability).

So, even though the press could easily generate far in excess of 200,000 psi in a .172 die without straining itself, the die would be blown to bits before the gage read 600 psi. And even though the press can, in fact, produce 200,000 psi, if you had a .512 diameter die installed, the maximum pressure you will ever generate with the press set for its maximum of 2000 psi is 80,580 psi in the die.

Don't let the pressure scare you. When a die blows up, it releases all the pressure as soon as a crack forms. There is very little energy packed into that pressure. A firearm holding back 80,000 psi would have a tremendous amount of stored energy at that level. A swage die has only a tiny bit by comparison. As soon as the die breaks, the pressure is gone.

Dies usually break in two parts, very neatly. Core swage dies, which have three bleed holes at 120-degrees around the circumference, usually break through the bleed holes because that is the point of least resistance. Sometimes they will break and remain connected, so you barely notice it except for the loud "bang" that the 200,000 psi alloy emits when it breaks. It is a little like the amount of energy stored in a bike tire versus the energy stored, at the same pressure level, in a big air compressor tank. Both might be 90 psi. If one breaks, it throws a bit of rubber a few feet. If the other breaks, it takes out the building!

Since it is quite important to control the pressure, and it is obvious that you can easily break some of the dies with very low gage readings, it becomes important to know how to determine breaking pressure. The Hydro-press has pressure controls that give you complete ability to set the limits to safe levels for any die.

A chart in the back of this book lists all standard calibers and their breaking strength in a conventional Hydro-press die. The breaking pressure, ram thrust, and gage pressure are all listed. As long as you read the maximum gage pressure in this chart, and set up your press so that it cannot possibly reach or exceed this level, your die cannot be broken from excess pressure, with two exceptions: (1) point forming dies have a curved ogive shape which effectively reduces their bore size as you approach the tip, and (2) dies with bleed holes can be broken if you try to force high strength material through the tiny holes or try to move normal material through them too fast.

In effect, in both instances, the actual bore diameter where the pressure is being applied is much smaller than the caliber of the die. Instead of using the caliber, you need to use the diameter of the hole where you intend to force material under pressure. In some cases, the hole is very tiny indeed, and the ram thrust must be reduced greatly in order to limit the pressure at this point.

If you put a small, hard piece of metal (such as a copper rod or brass jacket) into a tapered cavity (or point forming) die and force it to expand to fill the die cavity, you will be applying concentrated force against a smaller diameter than the actual bore (shank portion) of the die. To calculate the safe limit, use the diameter of your rod or jacket at the point of initial contact instead of the die caliber, and set your limit for that bore size.

I need to stress that the hardness of the material that you are swaging has absolutely no effect on the pressure that you decide to apply. Sometimes a person will crack a die because they put a hard lead alloy or a piece of solid copper into a die, and then just kept applying more and more pressure because the material would not form at a normal, safe pressure. The hard material did not crack the die. The pressure that was applied did it. You are in complete control of the pressure, and can stop trying to form any material that is too hard any time you wish.

Likewise, using soft enough material in the die only guarantees that it will flow and make the proper shape bullet at a safe pressure. It does not automatically reach over and grab the pressure control and turn it down to the safe pressure you ought to be using. Certainly you can leave the pressure turned way up from forming a .458 bullet and blow up a .224 die using anything for material. It is really wishful thinking to send a broken die back with a note saying "This die must be defective: it broke using soft lead".

Corbin offers a low-cost computer program that can calculate the breaking strength of any swage die, for any caliber, diameter, or material strength, and also translates maximum pressures from one system to another, so that you can easily determine the pressure within any caliber of die regardless of the cylinder size or gage reading. This is available under the catalog number DC-DIES. (It isn't actually an obituary.) A pressure-related program that concentrates on wire extrusion, powder metal compacting, and press designs, is called DC-LEAD. Both are useful in the design of swaging and extruding presses, and in using the proper levels of pressure.

Die pressure is easy to calculate. It is merely the ram thrust divided by the area of the punch tip. No matter what shape the punch tip may have, if you look at it straight on, it has an area that corresponds to the bore of the die. For practical purposes, you could say the die bore area is the same.

But, remember that the caliber is not the same as the diameter when you have a core swage or core seating die. The core swage must be smaller by at least twice the jacket wall thickness. That can make a considerable difference in the pressure calculations. With a core swage die, use the punch diameter. Do the same for a core seater. The jacket effectively reduces the area when you are seating cores. All the ram force is pushed through the area of the punch tip.

This means you could use the .375 caliber chart to find the limit of pressure for a .375 core swage die and blow it up as a result, since your particular set might use a .065" wall jacket and thus the core swage would be more nearly .243 caliber!

Here is the formula for determining maximum internal die pressure...

P_max = (2st² + 2stC)/(2t² + 2tC + C²)

where...

t = the thickness of the die wall, and...

C = the caliber or die bore

s = tensile strength of the die material

The thickness of the die wall is merely...

t = (D - C)/2

...where

D = outside diameter of the die

C = caliber or die bore

The thickness necessary to hold any given pressure is found by using this formula...

t = (C/2) * (SQR((s+P_max)/(s-P_max))-1)

...where

C = caliber or die bore

P_max = maximum internal pressure

t = die wall thickness

s = die material tensile strength

...and SQR stands for the square root symbol as in many programming languages.

I have written all the equations in a manner that would be simple to insert in computer statements, although raising a number to an exponent power is usually written like this: n^2 ...because there is no way to actually compile or interpret a super-script character in most programming languages. Also, I used sub-scripts to make the variables a little shorter and more clearly indicative of their value, whereas if you want to put these equations in a computer program, you'll need to make up distinct variable names.

In relation to the Hydro-press dies, the die wall thickness, "t", is found by using a die diameter of .900 inches. This is the diameter of the thread root and relief groove in the shank, the smallest part of the die. This area normally has little or no pressure acting normal to its inside surface, but it is better to be safe than sorry.

If you replace the "t" with the quantity...

(.900 - C)/2

...in the pressure equation, and replace the "s" with the 200,000 psi tensile strength of Corbin's heat-treated dies, then the equation reduces to...

P_max = (200,000 * 0.81 - C²)/(0.81 + C²)

This is a specific equation for the Corbin Hydro-press die series, which are the "type -H" dies. They can be used in the Corbin Mega-Mite^tm, Hydro Junior^tm, and Hydro-Press^tm models.

To find the gage pressure for the Corbin Hydro-press, you can use this formula...

P_s = (3.25 * P_max * C² * Pi)/8.2957679

You're right: the tables and the software program are a lot quicker. The program runs from a simple menu. You can generate information about any kind of die material, diameter, caliber, gage pressure, translate one system pressure to another, find ram tonnage and thrust, and much more—hundreds of pages more information than I could possibly print in this book.

Die pressure, then, is something that is related to press tonnage but has many other factors. The pressure you actually need to use, versus the pressure that the die can withstand, both need to be translated to a gage reading for your press, so that you can easily set and monitor the safe operating pressure level, always using the least pressure that gets the job done consistently.

The tables in this book make it simple with the Corbin Hydro-press system, and are one reason why it makes good sense to consider a standard, well-tested and researched system even if you are perfectly capable of building your own press or have access to any number of powerful presses. The data relating to their use would have to be developed by rather costly experimenting. It has already been done for the Hydro-press system.

In the years 2000-2003 I supplied Hydro-presses to the U.S. Army advanced armament research and development lab (AARDEC) at Picatinny Aresnal, and was asked to come to the New Jersey facilities a couple of times to train researchers in the use of the press and dies for the "Green Bullet" project. This was a much-publicised initiative to convert of most of our military small arms ammunition to use environmentally friendly projectiles.

The concept of "safe" bullets caused some humor but really, the idea makes sense since far more bullets are fired in training than in combat. The bullets all land on our soil, at the various training bases.Millions of rounds of lead eventually build up in the berms to each toxic salts into the water tables. Most of the bases are located near large population centers, so contamination of the water table is a concern. No one actually gives a hoot whether the next sniper round that hits a terrorist is filled with potentially toxic metal or not, although that is where the jokes were all aimed.

When I arrived the first time at the lab, I was met by two Ph.D's in physics who were in charge of the actual research, both of them civilians. The Hydro-presses were set near the end of a nearly block-long building that probably dated from the 1920's. Inside were millions of dollars worth of laboratory gear, including a hydrogen atmosphere furnace and a giagantic hydraulic press that stood at least two stories tall through a huge cut-out in the floor, where a basement was excavated to make room for at least half of its height.

During our conversations, I asked Dr. Kapoor, the main fellow in charge at that time, why they bought CHP-1 presses instead of just using some of the existing massive equipment. He paused for a second, weighed his thoughts, and said, "They do not have the control we need." Then he turned and indicated the monster press that was lurking just over our shoulders, and muttered, "We are afraid to use it."

At first I thought this was a joke, but the further I became involved in the project, the more I realized the wisdom behind the comment. We were working very close to the dies, metering in precise amounts of powdered metals and swaging them one at a time to test the results. The pressures were experimental and the results were not yet known. Some operations shattered the punches the first time they were tried. Without the precise control of position, pressure, and timing, it really could be dangerous to try some of these things with the much more expensive machines already in place.

We also supplied tooling for Oak Ridge National Labs, Sandia Labs, Lockheed and to Martin-Marietta when they were separate concerns (that puts the date stamp on me), to DuPont Textile Division (during Viet Nam for development of woven aircraft armor), to Lawrence-Livermore Labs, and to folks at the Los Alamos labs, among many facilities who had the resources to get anything they wanted. I know that if someone wanted to spend the money, we could build fancier presses, bigger presses, presses with more automation. But the performance of the standard CHP-1, which you or anyone else can get from stock 90% of the time, was just right for the task of building serious prototype bullets.

I mention this not from an excess of ego (I got over that a long time ago when I was shooting on a Navy pistol team sponsored by the officers of the guided missile frigate U.S.S. Daniels out of Norfolk, came in second to a gunny sargent of the U.S. Marines, and had to sing the Marine Hymn to the other team). Naturally I'm proud that our equipment has been selected by so many top arms developers, and of any small role it might have played in advancing our country's defense.

But my real point is that you don't need to spend more money on a system to get exactly what most serious research and development people use. You can be certain that if there was anything better suited to developing prototype projectiles, none of these agencies would have purchased anything less. As it was, they saved thousands of dollars over the next nearest priced, similar quality press and got exactly what they needed. That's our tax money being saved, yours and mine!

Whether or not you agree with the wisdom of what was developed, it would have been developed anyway by someone. That being so, the best thing for all of us is that American research and development people have the most cost effective solution. Not the cheapest, because that may be shoddy and ineffective in the long run. Not the most costly, if it doesn't really provide useful value for the extra money. But the equipment that gives them the most useful tool for the job. If it leaves money in the budget for something else, that's even better.

Lead wire extrusion can be a profitable adjutant to bullet manufacture. It is useful in the bullet-maker's own product line rather than using purchased lead wire or casting cores. Lead wire can be sold to fishermen, sporting good stores, and other bullet makers with a return of up to 400 percent on investment.

Unfortunately, even with such good rates of return, the market is not large enough to support full-time lead production in most areas. But as a supplement to other products, lead wire brings in enough to more than justify the initial investment.

The commercial production of lead wire requires a power press. A hand press is too slow, and does not develop enough power to handle the required volume in one billet except for very small wire sizes. It will be shown later that almost any press can extrude lead wire, but with the exception of very small diameters, the length of lead you can extrude in one stroke with any hand press is not enough to justify the attempt.

Lead extrusion requires that the raw lead be formed into a billet (a cylinder of lead that will fit into the extruder die) by casting. There are three ways to get the billets. One is to cast them yourself. This requires a large lead pot such as those used by smelters. It also requires natural gas or propane, since electric heat is rather expensive for this operation.

The fire danger, health hazard, and physical location may all combine to make casting scrap lead into billets an impractical task. Billets can be purchased from a lead supplier. This reduces the profit in many cases to as little as 100% return on investment. However, it eliminates some of the investment and all the fire insurance, zoning, and health problems associated with melting lead.

Another alternative is to put someone else in business as a part-time supplier of lead billets for you. Find someone who has a country location, who doesn't mind the fumes and has room for the big lead furnace, and who would enjoy spending a few days every month melting several hundred pounds of lead, perhaps several thousand pounds later on.

The molds can be honed tubes fitted to steel bases. Corbin makes billet molds from cylinder tubing, hones them smooth inside, and fits them to self-supporting bases. The tube slips over the plug base. Molten lead is poured into the tube and allowed to cool, and another billet mold is filled in the interval. Then the first one is picked up and an empty tube placed over the same plug base.

Every few pours, the first tube is given a rapid vertical shake (with five pound or smaller size billets — a machine is used to push the billets from larger mold tubes). The lead billet slides out, and the empty tube is put back on the base again.

Billet sizes from one pound in .79 inch diameter (used in the Hydro-press) to 25 pound size in 4-inch diameter are typically used. A tiny extruder for the reloading press or S-press, used to make small amounts of .120" lead wire for sub-calibers, takes a billet of only about 500 grains. That is typical of what one can extrude with a hand press.

It is common for people to under-estimate the size of hydraulic system required to extrude a given size, weight, or length of lead wire. The Hydro-press, for instance, runs an oil pressure of 2000 psi on a 3.25-inch cylinder and can extrude a .79" diameter billet that weighs about one pound.

The a 10-pound extruder system utilizes a cylinder with an eight inch bore, running 2000 psi. This press has a ram force over 100,000 pounds, which is fifty tons. It can extrude soft lead wire from a billet of up to two inch diameter, through a hole as small as .125 inches. Using a six inch bore drive cylinder, with 2000 psi, the minimum wire diameter that can be extruded is .185 inches from a billet no larger than 2 inches. This is a force of 56,520 pounds or 28 tons.

With a four inch bore cylinder and 2000 pounds, it is barely possible to extrude a one-inch diameter billet through a .312 inch hole. Practically speaking, it would be best to limit the extrusion to no smaller than .365 inch diameter wire. This is a ram force of 25,120 pounds, or 12.56 tons.

The lead hardness, temperature, pump pressure and ratio of the billet cross-sectional area to the cross-sectional area of the extruded wire is what determines how big a cylinder will be required. The weight of lead produced from one billet can then be determined from the length of the billet. A practical length for a cylinder of reasonable price is not greater than four times its bore diameter.

That is, the price of a typical four-inch bore cylinder starts to become excessive, compared to a larger bore cylinder, when you look at lengths of stroke greater than 16 inches.

The price of a six-inch bore cylinder longer in stroke than two feet would pay for getting an eight-inch bore cylinder in most cases, and the price of an eight-inch cylinder with a stroke of 32 inches or more would just about get you a ten-inch bore cylinder. This assumes that you are attempting to extrude the same volume of lead.

Volume of lead goes up directly, cubic inch per linear inch, with cylinder stroke length. But it goes up with the square of the cylinder diameter. So, you have to double the stroke to get twice the volume, but you only need to increase the diameter by 1.41421356...

If you are paying more than twice as much money for doubling the stroke, yet are paying less than twice as much to increase the bore size at least 1.414 times, then you are getting more lead volume extrusion for the money if you select the next bigger cylinder diameter.

Of course, we are talking about cylinders that cost thousands of dollars here, so lead extrusion in large volume is something to consider carefully. Cylinders large enough to handle a four-inch billet, for example, and extrude wire in the practical range of from .125-inch to .5-inch diameter in spools of 25 pounds would have to be nearly a foot in diameter and have a stroke twice the billet length, which in a four inch, twenty-five pound billet means a 20 inch stroke.

Such a billet would produce 414 feet of pure lead wire in .125" diameter, or about 66.5 feet of pure lead wire in .312" diameter. If the lead was not pure, but had a density of .393 lb/in³ instead of .4097 lb/in³, then the first example would produce 432 feet of lead in .125" diameter and the stroke would have to be almost an inch longer to handle the extra volume.

In the second example, a .312" diameter wire would turn out 69.3 feet long instead of 66.5 for pure lead, and the stroke length would be just about an inch longer to do it. As the hardness of lead goes up, the density goes down, and the volume required for a certain weight goes up. Unfortunately, lead hardness greatly increases the necessary pressure for extrusion. Typically, lead wire is pure lead, 99.995% being the purity supplied by Corbin in 10-lb spools.

The formula for determining the weight of lead in a given billet size is...

W = 0.7854 * B_d² * B_L * Dens

...where

W = Weight of billet (or spool) in pounds

B_d = Billet diameter in inches

B_L = Billet length in inches

Dens = Density of the lead in pounds per cubic inch

Conversely, the length of billet and stroke in a machine with removable die (so stroke is only marginally longer than actual billet length) is found by the formula...

B_L = 1.273 * W/(B_d² * Dens)

Typical lead density for soft lead is 0.4097 lb./cu-in. It can range to .406 lb./cu-in without causing undue concern. Less dense alloys are hard to extrude, and may crack. Extremely hard alloys come out as coarse powder, or at least as very fragile rod that breaks up far too easily to be coiled, depending on the formulation of the alloy.

The formula for determining necessary extruder pressure for a given size of billet is proprietary, since it cost so much to develop in both equipment and time. You'll have to forgive me for not including it in this book. I'm not anxious to give potential copy-cat competitors that much help!

I will give you a formula that represents an approximation of the required force, though it doesn't consider some of the innovations we've used to make our systems more efficient. To determine the drive cylinder diameter required for a given billet diameter to be extruded to a given wire size, you can use this equation...

D_c = 1.273 * (1/P) * (B_d/W_d)² * s

...where

D_c = diameter of extruder cylinder,

P = system pressure, psi

B_d = Billet diameter in inches

W_d = Wire diameter in inches

s = tensile strength of the lead

This formula will give you an idea of the size of drive cylinder required to extrude a given billet into a given wire diameter with a given amount of oil pressure available. There is also a software program available from Corbin that will instantly calculate wire length, billet length, spool and billet weight, wire diameter, lead density, and other parameters related to wire extrusion. It is called DC-LEAD, and also includes optional calculations for powdered metal bullet swaging, such as effective density, compression ratios, and powdered metal mixtures.

Extruders can be built vertically or horizontally. A vertical extruder takes up less floor space, but is more difficult to move and to load and unload. A horizontal extruder is easier to transport and can be easier to use, but takes up more floor space. Also the drag caused by gravity means that the cylinder, die, ram, and other components will tend to sag out of alignment unless the entire assembly is constructed with heavier framing than a vertical one.

Using a six-inch diameter extruder for making five pound spools of lead wire with a two-inch diameter billet, the head plate that keeps the die in place and resists the thrust against the extruder ring needs to be two inches thick if machined from cold rolled steel! Otherwise, even with four stout tie rods, the plate will probably warp under normal operating force.

There are two ways to push the lead out. One is to move a piston behind the billet, forcing the entire billet to move along the die. This is traditional and works well if the ratio of die length to diameter is not too great. The friction of the lead along the die walls can greatly increase the required force, otherwise.

Lead wire extrusion requires lubrication of the billet. A generous wipe-down with Corbin Swage Lube will cut the resistance along the die walls by half, making it possible to extrude wire in smaller sizes. If appropriate measures are taken to reduce the force required, harder alloys than pure lead can be extruded. But there are practical limits to the hardness of lead that can be extruded.

It is best to avoid lead with more than 6 percent antimony, or equivalent hardness in a tin-lead mixture. If the hardness goes over Bh12, it is likely that the lead will extrude poorly or not at all. Wheel weight alloys vary considerably over time and from region to region. Wheel weights are not standards to judge hardness, and can contain zinc, sand, tin, antimony, arsenic, and other materials. Extruding lead with sand and road grit mixed in it will soon wreck the extruder dies.

Reclaimed battery lead is one of the major sources of commercial production. More lead is reclaimed from automobile batteries than is mined, making lead one of the most recycled of all metals. Battery lead is not safe to reclaim at home, however. Alloy removal is a dangerous process for anyone but a smelter. It involves deadly gasses, boiling lead (something that puts lead vapor into the air in uncontrolled environments), and is generally not feasible at home.

Lead sold as "pure" may in fact be reclaimed battery lead with 99.95% lead and a trace of silver. Lead that contains more than one tenth of a percent of other metals is certainly not pure, however, even for our purposes. If it has a tensile strength of 1000 or less, and a hardness of Bhn 5, we can safely assume it will work as well as "pure" lead, regardless of its actual composition.

To determine the Brinell hardness number, you can perform this relatively simple procedure:

1. Obtain a known pure lead sample, and melt it into a bottle cap.

2. Prepare another bottle cap by filling it with your test material.

3. When both bottle caps have cooled, place a ball bearing between them, sandwiched against the two lead surfaces. The bearing should be from 5mm to 10mm in diameter.

4. Squeeze the sandwich in a vise so that the ball bearing is driven part way into each lead surface, but not as far as half way.

5. Measure the diameter of the two dents with a dial caliper, square both diameters, and divide the smaller number into the larger one, then multiply the answer by five.

The answer is the Bhn of the unknown sample. The accuracy is limited only by the purity of your soft lead sample, and your ability to read the diameter accurately. Corbin can supply pure lead samples for comparison testing.

Heating the extruder die to increase the ductility of the lead, and reduce the system power requirements, is an alternative to building a larger extruder. However, it only works moderately well in spite of the potential reduction of 50% in the resistance for every 100 degree increase in temperature. The reason is the thermal mass of the system.

The extruder die would have to adsorb and hold a vast amount of heat in order to maintain the lead billet at a high temperature during extrusion. Bringing the die and its associated massive steel supports to a temperature several hundred degrees above ambient level would cost a great deal in both time and electricity.

As soon as the lead is inserted, it begins to transfer heat to the frame of the extruder. The mass of the lead billet has to be heated completely through in order to reduce the resistance enough to make any difference. If the lead billet is first heated and then inserted into the extruder, by the time extrusion actually starts the lead will have lost most of its heat into the die and cylinder walls.

Thus, it would be necessary to pump heat into the die constantly. And since the steel would only transfer heat at a certain rate to the smaller surface of the billet, but would radiate heat at a faster rate from the greater outside surface area, the rate of heat transfer would have to be rather high from the source to the die. The outside of the extruder would need to be insulated to reduce radiation.

Most wrap-around heaters don't provide enough caloric volume, or quantity of heat in a short enough period of time, to make the extruder operate continuously. You would have to shut down everything but the heaters every time you loaded a billet, and wait a fairly long time for the billet to heat up. Even if the billet is pre-heated, if the die and cylinder is not provided with a fairly powerful source of constant heat, the billet will cool too quickly..

The final problem is lubrication. Sufficient lubricant on the billet will reduce the required system pressure considerably with most extruder designs. In fact, leaving off the lubricant can cause the machine to stall completely, failing to extrude anything. But heating the billet normally causes the lubricant to become less effective, perhaps even oxidizing or becoming a fire hazard.

With larger extruders, system power can be increased to five, seven and a half, or ten horsepower using 220 and 440 volt three-phase motors. This means that such machines could not be run in a home environment, since three phase power is typically not available there. But it does increase the margin for flaunting the rules. With enough power one can skip lubrication without stalling the machine.

Speed of extrusion is quite fast even with very slow ram movement, since the speed is relative to the diameter of wire being produced. The volume of lead that passes a point is constant whether in the die at full billet diameter, and moving at only a few fractional parts of an inch every second, or whether the point is taken outside the die, where the much smaller diameter means that the same volume of lead now is packed into a much longer piece.

Moving the same volume at smaller diameter automatically means moving more feet per minute past a given point. So, the ram moves slowly, but the lead shoots out like someone stepped on the toothpaste tube! In the Corbin's 3/4-inch LED-1 extruder for the Hydro-press, the ram moves about an inch per second, taking nearly five seconds to push the entire billet out the die. But during that time, the lead comes out fast and hot — you have to wear gloves to avoid unpleasant burns.

The movement is fast enough with small diameters so that it should be guided into a box using a long piece of plastic guttering or large diameter tubing arranged to catch the lead when it spurts out of the die. An angled deflector arranged over the die top will direct the lead wire in the direction of the chute, and once it is aligned and moving down the chute, it will head for the box faster than a person could guide it by hand.

The formula for determining how fast the lead is going to come out is...

R_w = (B_d/W_d)² * R_b

...where

R_w = Rate of wire movement, inches/second.

B_d = Billet diameter, inches.

W_d = Wire diameter, inches.

R_b = Rate of ram travel, inches/second

A rate of .5 inches per second on a two-inch billet translates to 233.7 inches per second when extruding .185-inch diameter wire. That is 19.48 feet per second, fast enough to make you notice.

When extruding wire, it is critically important that you never place your body over the opening of the die. In other words, have the wire bend around a guide or feed it onto the spool in such a way that no one is ever in the line extending from the bore of the extruder ring die.

This advice could save your life. I have seen lead wire trap a bubble of air or lubricant, and compress it between two pieces of the billet (especially when someone puts two sections of lead into the die instead of one solid billet). The pressure inside the extruder is extreme. There is a fair amount of energy stored in the compressed air bubble. It moves forward until it is just below the opening, with a piece of lead in front of it.

This is a blueprint for a high powered air rifle! There is a lead wire, acting like a bullet, in front of a bubble of compressed air that will move, in a fraction of a second, just into the opening of the extruder ring die. If the bubble is about the size of the extruder die hole (wire size), then nothing connects the rapidly extruding wire to the billet at that second. It is free to fly.

There is a hole in my garage ceiling, right through the plywood, where one of the first extruders fired a shot in this manner. Fortunately, no one was peering down into the die to watch the lead come out. I have only seen it happen twice. But it can happen. Beware! Treat the end of the extruder as if it were a loaded rifle. Put a guard or shield in its path, or make sure it points the lead in a safe direction as it comes out.

And don't reach in front of the die when you are spooling the wire. This was from the Hydro-press extruder, which used a .79-inch billet and a 3.25-inch drive cylinder at 2000 psi. Of course, the lead pressure is about the same in any extruder system. It is only the ram thrust that goes through the roof as the billet size is increased. Lead still moves at the same internal pressure no matter how much of it there might be in the die. The length and die shape create friction that is significant, but still the pressure required to flow lead is dependent on temperature and alloy. It has nothing to do with the rest of the system.

Extruders can be made, as I mentioned, in a fixed or removable die version. With the fixed die version, the stroke must be long enough so that a billet can be placed behind the die and pushed into it. The stroke is twice the billet length plus at least twice the diameter of the billet to allow alignment. You simply drop a billet onto a guide, or drop it into the die from the top in a vertical system. The ram then moves "fast forward" as quickly as oil can be pumped into the cylinder, often using a dual displacement pump with automatic shuttle valve to switch to high pressure and slower movement when resistance is met.

To use a foot-long billet with this system would require a two foot ram travel plus a bit more for alignment room in the die. This adds to the cost of the system, so another method is also used. The removable die can take several forms. Two of them are the cup die and the open tube die.

The cup die is closed on one end or has the extruder ring mounted in it (so it is nearly closed). The tube die is open on both ends and is closed either by having a screw-on or bayonet-lug fastening, or by fitting snugly against a base when it is in the machine.

The cup die is removed from the machine, loaded with a billet, and placed back on the machine. Several dies could be used, but they are quite expensive. The tube die can be fixed to the machine and have a removable end cap to load in the billet.

It too can be removed, but since it is open on both ends, it is lower cost to make and can be loaded from either end. The wall thickness of the die can be calculated using the same formula as for bullet swages. The punch is actually a ram. It can have a floating head that aligns in the die, or the assembly can be made very rigid with a solid head, and precision of the unit will keep the ram centered in the die.

Because the forces are so high in such a system, the ram can be driven into the die wall if there is any misalignment, destroying the die. It is critical to keep punch and die alignment in the range of 0.001 inches or less. This is not great precision in a die only an inch long, but when the die is as much as two feet long, and weighs fifty pounds or more, it can be a problem.

A variation on the tube die is the pivoting die, wherein the extrusion cylinder is hinged to the press head and the extruder orifice is mounted in the head. To load this press, you swing the cylinder to one side, insert the lead billet, and then swing the cylinder back into alignment with the ram. The hinge and the locking pin that secures the cylinder to the press head must, of course, be very stout.In some extruders, an auxillary ram moves a tubular clamp forward, surrounding the actual pressure ram, and uses this to hold the extruder cylinder in place against the press head.

Extruders can also make hollow lead tubing with only slight modification. A billet is cast using a wire stinger in the middle of the tube mold. The hole through the billet lets you mount a fixed rod or wire in the center of the extruder die, passing out the ring die opening. As lead is extruded, it flows both through the die hole and around the central wire, leaving a hole through the center of the entire spool.

The force on the wire is extreme, so that 1/8-inch wires have been pulled apart during extrusion. Spring wire is normally used for strength. The purpose of hollow lead wire is for solder, primer cord sheath, and acid tubing. It can also be used for fishing sinker wire. Lead wire can be formed in various geometric shapes, for the stained glass industry. This form of lead extrusion is called "came". It is often formed as H-shape cross section channels, to hold two pieces of glass together or as a U-shape cross section for edging. The shape comes from a carefully cut and polished extruder orifice.

The actual die insert or orifice is normally made with the side facing the lead as a very slight angle to a smooth radius that leads to the tightest constriction right away, not as a deep funnel. There is frequently a relief hole on the output side, or a counter-bore, which reduces the amount of drag applied to the lead wire while maintaining the strength of the die.

In most cases, you cannot insert a second billet and have it join the wire from a previous billet. The junction is usually poor, and separates when the wire is coiled on a spool. Oxides and carbonates form on the surface of pure lead almost immediately in our atmosphere. This is what makes lead stable and protects it from further deterioration. Some forms of lead decomposition are porous and flaky, but the most common oxidation forms a tough film that resists further deterioration. Unfortunately, it also resists binding with another piece of lead, since there will be two layers of oxide between the pure lead.masses. The billet size should be an even multiple of the weight of your finished wire spools, plus a small amount for scrap that is always left in the orifice die and should be pushed out or cut off the end of the next extrusion.

To sum it all up, lead wire can be a profitable product for the bullet maker as long as the size of the system is kept in reason. All considered, the beginning bullet maker may wish to produce wire in short pieces, perhaps a foot to eighteen inches long, using the LED_1 extruder kit with the Corbin Hydro-press, rather than purchasing a large extruder system. Wire can be packaged in straight lengths and sold this way, rather than on spools.

Then, after having established that there is a market for lead wire, and arranging for someone to produce larger billets at a reasonable cost, a machine capable of running five to ten pounds of lead at one time might be feasible. To produce more than this becomes quite expensive, and involves logistics of an industrial nature: power, space, and noise as well as the licensing and environmental concerns may push the idea beyond practical limits.

In order to determine just how big a system you might need, in terms of pressure and drive cylinder size, run the program "DC-LEAD" with the particular alloy hardness, wire diameter, and billet size that you want to use. It may surprise you just how large a system it takes to produce a ten pound spool of wire with the smaller sizes.You'll also quickly see one of the reasons that alloyed lead wire is infrequently found on the market. The size of system required increases rather dramatically as you increase the hardness and thus the resistance to flow.

Another reason why alloy lead is harder to find in wire form is that there are infinite ratios of lead to other alloying agents. Unless a firm were to take custom orders rather than selling from stock, it would be hard to know what to stock. Cash flow could be severely restricted, because too much inventory would sit on the shelves unsold, locking up money that should be working. A custom "fabricator", as the lead extruding firms are called, would need to secure an order large enough to justify melting and mixing enough to pay for cleaning out the pot before and after, and for extruding enough material to use at least one complete billet for their size of machine.

In most instances, a commercial lead supplier needs to sell from half a ton to a full ton at a time in order to make the run worthwhile. If you only want to buy 50 or 100 pounds of alloy wire, it would be a little like asking Winchester if they'd make you a couple of pounds of gunpowder in some special formulation so you could try it.

This presents an opportunity for a home business to make and advertise small runs of alloy lead in national gun magazines. The LED-1 extruder die isn't suitable, but a custom die can be built, and for that matter, we have built dedicated custom extruder machines