Corbin Handbook
of
Bullet Swaging
No. 9
by
David R. Corbin
Corbin Manufacturing & Supply, Inc.
PO Box 2659
White City, OR 97503 USA
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Corbin Handbook of Bullet Swaging No. 9
by
David R. Corbin
Corbin Manufacturing & Supply, Inc. PO Box 2659 White City, OR 97503 USA
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Corbin Handbook of Bullet Swaging, No. 9
© Copyright 2004 David R. Corbin
All rights reserved. May not be reproduced by any means, including electronic and mechanical, without the expressed written permission of the copyright holder.
Published by:
Corbin Manufacturing & Supply, Inc. PO Box 2659 White City, OR 97503 USA
541-826-5211 Mon-Thurs 9am-5pm
Fax: 541-826-8669 24/7
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1. Introduction to Bullet SwagingGood morning! I'm Dave Corbin, and for over 30 years I've had the second best job in the world: I help people make the state-of-the art bullets that you've read about in the gun magazines. Nearly every custom bullet maker started with equipment developed at the Corbin die-works. They have the best job in the world! All you have to do is scan the pages of nearly any magazine catering to handloaders, and you'll see dozens of ads from our clients; the articles are constantly talking about the bullets our clients make, and the major ammunition firms are buying the bullets made on Corbin equipment for use in their premium ammo. There has been a lot more research and development that you don't read about, because it isn't intended for the general shooting public. I can now include a small amount of that information in this edition. Corbin Manufacturing publishes a book called the "World Directory of Custom Bullet Makers" listing hundreds of individuals and firms whose names you may recognize if you are familiar with handloading. When I read the list, I remember someone's enthusiasm for the new business venture they were able to start, thanks to the power of bullet swaging. Olympians and world champions in every field of firearms sports, from benchrest to air gun competition, using everything from paper-patched blackpowder bullets to custom fin-stabilized shotgun slugs, have come to the die-works where we have toiled for the last quarter century and into the first quarter of this one, some just to improve their already-outstanding achievements, and some to help others become better shooters by manufacturing new ideas in how a given bullet should look and be constructed. Engineers from the Department of the Army, Air Force Armament Labs, Sandia National Laboratories, DuPont, Northrop, Lockheed, Martin-Marietta and other defense-related organizations have visited us over those years, sometimes sketching ideas on napkins during lunch. Tools and designs we worked on are in use today all over the world, wherever a long range, high precision projectile or a very special purpose bullet that could only be made efficiently by the high precision techniques of swaging, is needed for the job. Whether it is protecting an important public figure at long range or picking a pine cone from the top of an experimental tree, whether it is surveying a dense mountain jungle with remotely launched flare projectiles designed for vertical firing stability, or stitching mirror-based bullets in an arctic ice sheet from a low-flying aircraft so a laser beam can measure the depth and estimate the strength of the ice to hold a transport plane, or whether it is the grim responsibility of instantly stopping a terrorist before he can take the life of another hostage—regardless of the purpose, we sat through many meetings pouring over blueprints, computer readouts, and sketches, helping design projectiles for visitors from the far corners of the earth. | |||
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Yet, this work is only the continuation of development begun by other pioneers of bullet swaging: people like Ted Smith, who founded the old SAS Dies in the 1950's; Harvey Donaldson, who experimented with some of the first dies to make .224 bullets from fired .22 cases; Walt Astles and Ray Biehler, who developed the principle of upward expansion and the two-die swage technique which replaced the RCBS single-die take-apart system; Charlie Heckman, a pioneer swage maker; and so many others whose names are probably unknown to modern shooters, but to whom all shooters owe a debt for their contributions to the perfection of bullets. You may know that the RCBS company (initials of which mean Rock Chuck Bullet Swage) got started making bullet swaging equipment, but soon dropped it in favor of more easily produced reloading dies. You may even have heard Speer Bullets was started by Vernon Speer swaging .224 caliber bullets from fired .22 LR cases. But bullet swaging played a much larger part than just that, in leading to the products and companies you use today: Hornady, Sierra, Nosler, Barnes, Swift and a host of other mass production operations owe their very existence to the concept of bullet swaging. Today, more than four hundred custom bullet firms—operated by people who probably differ from yourself only in having taken the step of putting their intense interest in firearms to work at a profitable and enjoyable occupation—produce specialty bullets. We call this field "custom bullet making", the elite corps of bullet manufacturing providing initial concept advances sometimes copied years later by the larger "mass production" bullet makers. So, what is bullet swaging and how do you do it? What do you need to get started? How much does it cost? What are the advantages and drawbacks compared to casting or just buying factory bullets? Can you swage hard lead, make partitioned bullets, make your own jackets, make plain lead bullets or paper patched slugs? I answer those questions a thousand times a week and I never get tired of it. But to save you a lot of time on the phone, I've written most of those answers here. If you read through this book and think I have left something out, you are absolutely right: I left out about seven more books of information! Those are available if you care to read further. Swaging is so simple you can do it correctly after just a couple of tries. Then you'll see it's also extremely versatile and powerful: you can do one more thing, and then one more after that, and soon you will have the whole top of your loading bench covered with one-of-a-kind bullets, some of which no one in the world has ever made before. That's why it takes at least seven more books to make a dent in the vast array of things you might do, could do, if you wished. Only your imagination limits the possibilities. A deeper study of the specifics of bullet swaging technique and tooling, including products made by people other than Corbin, can be found in the book "Re-Discover Swaging", so named because swaging was, in fact, discovered once before and then almost lost: during the period of 19481963 there were many die-mak | |||
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ers who produced swaging equipment, but none of them offered a comprehensive enough range of products to insure their own survival, or that of the swaging arts. Corbin Manufacturing was the first comprehensive effort to preserve and further the technology with information, supplies and tools from one source. Whereas other die-makers tended to be secretive and often died with their secrets of bullet making, Corbin began publishing information that would help advance the field, from our beginning days. Bullet swaging, by the way, is pronounced "SWAY-JING" and rhymes with "paging". There is a blacksmith technique for pounding hot metal around a form that is called "swedging" but it is a different sort of thing altogether. If you want to really dig into the subject and learn things most people never discover, then order the Book Package. You get another copy of this book free, with it. Give this copy to a friend. Who knows: maybe between the two of you, a new bullet making business may develop that rivals the fame of some of our other clients? It could happen: it has happened over 400 times so far!
Warning! While the majority of handloaders say that they enjoy reading the additional side trips that clutter my books, some have complained that I don't get "to the point" and just tell them 1-2-3 how to make a bullet. I agree that this would be a good idea, if only I had some way to know exactly which bullet they wanted to make. You see, every bullet can be described with a step-by-step, cookbook approach, but there are tens of thousands of different styles and shapes you can make, and not all of them are made the same way! The same bullet may be made in slightly different ways with different presses and the dies which fit them. Instead, I try to teach the principles involved. That way, you know the terminology and won't be confused by thinking a die is a punch or a punch holder is a die. You will understand that every swaging operation expands the components upward in size, so that you won't try to put a larger part into a smaller hole except when drawing down (which you will know is different from and opposite to swaging). You will know that in a swaging press, the die screws into the ram and the external punch fits into the press top, in a floating punch holder, whereas in an ordinary reloading press used for swaging, the die fits the top and the external punch fits the ram. You will understand that a smooth, step-less ogive requires a set of dies that includes a point forming die, whereas a shouldered semi-wadcutter style bullet can be made in a single die. All these things will be familiar to you before you start. You won't need to be told specifically how to make every possible bullet, because you will understand the basic principles and how to apply them to any bullet. When we ship orders for dies, they come with specific, simplified 1-2-3 instructions that apply to the design you ordered. Sometimes these instructions are applicable to many calibers in a popular style, so we print the instructions on a form. Sometimes your bullet design needs specific, handwritten details and tips we discovered while developing the dies, and then we write special instructions for | |||
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you. But in all cases, if you are prepared with a good background of general swaging principles, you can avoid damaging the tools and begin making bullets with higher confidence. Swaging versus CastingEveryone seems to be familiar with bullet casting (melting metal and pouring the molten liquid into a split mould, letting it cool and shrink, and then opening the split mould halves so that the frozen bullet metal can drop out). Casting involves a lot of time and introduces quite a few potential sources of inaccuracy, but it works reasonably well within a limited range of capabilities. You have to have a lead pot and a supply of lead, a mould and mould handles, then a lubricator and sizer machine to prepare the bullets. The sizer machine needs sizer dies and base and nose punches to fit the shape and caliber of bullet. It also require lubricant to apply to the bullet. The first thing you have to do with casting is to melt a pot of lead, flux it and stir it, make sure that the dross and dirt is cleaned from the lead, ventilate the room and make sure no moisture gets into the pot and blows the hot lead out with a bang. You need to be reasonably careful about fire and burns, and about potentially toxic fumes (no eating or smoking, plenty of good ventilation). After about half an hour of this melting and preparation, you are ready to start casting bullets. The first few attempts usually make incomplete or frosty bullets, until the mould is warmed up. During the casting process, the mould contains liquid metal that is cooled to solidify on every single bullet made, so it is constantly changing diameter from thermal expansion. When you open the split halves, part of the mould is exposed to room temperature air while the rest is protected from it, which cannot fail to slightly warp the roundness of the mould. The two halves of the mould cannot be put together with zero tolerance, as they would be far too hard to swing open and closed again, so there is some degree of "slop" in the fit of the pivot and the alignment pins. Add up all these factors and you can see that a cast bullet has a limit of roundness and diameter control based on physics, rather than skill or quality of manufacture. A swaging die runs at room temperature and does not contact hot metal. It flows the metal under tons of pressure, squeezing out all air pockets and voids. The bullet takes its shape and finish from the diamond-lapped hardened surface of the die. The die is not split, but is a solid tube or cylinder with thick walls to hold the pressure. The bullet material goes in one end, and is pushed back out the same way. Two precisely fitted punches seal both ends of the die. One moves in and out to load material, and the other acts as an ejector. The problems associated with heat expansion, swinging split section alignment, and the time required to prepare are absent or minimized with swaging. In addition, the die can make a wide range of weights depending on how much material you put into it. A mould makes approximately one weight because you must fill it to make a bullet. These are just a few of the differences between casting and swaging. | |||
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2. What is Bullet Swaging?Before we talk about swaging a bullet, we need to make sure the concept of a bullet is clear. When we say "bullet", we mean the projectile or part of the cartridge that is propelled through the air. The news media in the United States often refers to a "bullet" as the entire cartridge with powder, primer, bullet and case. Bullet swaging has nothing to do with the rest of the cartridge, but concentrates on the part that flies to the target. In some countries, shooters refer to the bullet as the "head" or the "bullet head" and call the entire cartridge a "bullet". There is a good reason not to call the cartridge a bullet, as the general news media seems inclined to do. The bullet is inert metal without any propellant involved, which means that it should be treated as a precise metal product, not some dangerous component subject to transportation restrictions and tariffs. A bullet is as safe as a writing pen, probably safer: people have been stabbed with uncapped ball-point pens. I accidently stabbed myself once, stupidly, reaching into a coat pocket. Finding a "bullet" in the possession of an airline traveller should be no more cause for alarm than finding a coin. Unfortunately, through ignorance and imprecise language, the term "bullet" causes problems where it should not. Some of them are of practical concern to those who show their products and must carry samples. More than one new bullet maker has run up against unrealistic insurance, business licensing and zoning problems because of ignorance about what a "bullet" actually means. A bullet maker is a precision metal product manufacturer, who could just as well be making precision bearings or electronic fittings. But try to explain that to a bureaucrat who just found out you intend to make bullets in the home enterprise, or the hysterical airline security guard who scanned a couple of samples in your pocket, or the customs agent whose eyes widen as he reads your declaration of "bullet-making" equipment being taken into the country! Such a pity these things happen. The wise bullet-maker soon learns to discuss precision formed parts rather than bullets, around those who know nothing about the field. Corbin equipment can swage bullets from .123 diameter up to about 1-inch diameter (.998-inch is the 4-bore blackpowder elephant cartridge, for example). The "bullet" can be an airgun pellet, a swaged round ball, a shotgun slug, a fragmenting shot or powdered metal filled jacketed pistol bullet, a partitioned or multi-jacketed projectile, and it can be made of pure lead, various lead alloys, powdered metals pressed together with or without a jacket, conventional jacketed bullets with a lead core with or without other inserts such as penetrators or light plastic fillers to shift the center of gravity and create fast, light but long projectiles. In short, just about anything that can be launched from a small arm, be it airgun, shotgun, rifle or pistol, and some kinds of machine guns and cannons, can be swaged and is considered a bullet. | |||
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Bullet swaging (SWAY-jing, sounds like "paging") is the process of applying extremely high pressures (from 15,000 PSI for soft, unjacketed bullets to as high as 150,000 PSI for solid copper bullets) to materials contained in a very tough, extremely well finished die, so that the material will flow at room temperature and take on the shape of the die and the ends of the punches. A die is a vessel to hold the pressure. A punch is a rod that fits into the hole in the die and seals off the end. If you refer to a punch as a die and vice versa, you may cause some interesting errors when placing orders. One of the first things to learn is the right names for the basic parts involved in the swaging process. You wouldn't call a pistol a shotgun, would you? Probably not, or else you might get some odd-looking mail-order holsters! A business that is good at making swage dies probably will be buried in orders, with long waiting lists. Waiting up to a year to get your "die" and finding out everyone thought you wanted the "punch" that you asked for may be frustrating. Use the right terms and avoid this problem.
In swaging bullets, you will always be putting a smaller diameter object (lead, jacket, or a combination of both) into a slightly larger die cavity or hole. Each step in swaging increases the diameter of the components, until they reach the final diameter in the last die. Swaging never reduces the diameter. You will only have stuck bullets and hard ejection if you try to push a slightly larger part into a slightly smaller hole. This is the difference between swaging and drawing. You never swage anything "down". You never draw anything "up". In drawing, you do push a larger part through a smaller hole, to reduce the diameter. This kind of die is a ring, not a cylinder closed on one end. The jacket or bullet that you are reducing is pushed through the ring, and is decreased in diameter when it comes through the other side. We use drawing to make longer, smaller caliber jackets from shorter, larger diameter ones. Also, within some narrow limits, it is possible to make a smaller caliber bullet from a larger one, although this degrades the quality of the bullet unless special conditions are observed. Usually the difference in diameters has to be within 0.006 thousandths of an inch when you reduce finished bullets by drawing. Jackets can be drawn much more than this.
A jacket is the "skin" of a bullet, usually made of copper or a copper alloy with zinc (most commonly 5% to 10% zinc). Jackets can be used, or not, depending on the bullet design. A jacket isolates the lead core from contact with the barrel, and allows the bullet to be shot much faster without friction melting the core and smearing it in the barrel, which is called "lead fouling". Enough of that spoils the accuracy and is hard to remove. We'll discuss jackets in detail later. Bullet jackets properly designed for swaging are always made smaller than the finished caliber, then expanded by putting lead inside them and compressing it with a punch. The lead flows to fill the jacket, then pushes the jacket out a few thousandths of an inch to meet the die wall, which stops the expansion. One end of the die is sealed with a punch, which stops the end from popping off the jacket. | |||
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If you try to use a jacket larger than the die hole, it can't spring back slightly when you release the pressure. In fact, if you push a jacket into a die that is too small for it, the jacket will be trying to spring back to original size, and thus pressing itself firmly against the die walls. This causes difficult ejection and is hard on the equipment. The right way to swage bullets is to use jackets that fit easily into the die by hand, and lead cores which are small enough to easily drop into the jacket. Jackets of course have some wall thickness, generally from 0.015 to 0.035 inches (although there is no rule that says you can't make much thicker jacket walls if you want them). To determine the diameter of lead core which fits inside, you must subtract two times the wall thickness from the caliber, and then subtract an additional five to ten thousandths of an inch to allow for easy insertion, tolerances in the lead wire diameter, and the fact that you may have two or three steps with a small amount of expansion in each, to get to final caliber. Basic swage diesThere are two basic designs of swaging dies made by Corbin. All the specific styles of dies are patterned after one or the other of these basic designs. One design is a cylinder with a straight hole through it. The other is a cylinder with a semi-blind hole, having the shape of the bullet except that at the tip, there is a tiny hole (.052 to .120 inches is a typical range) fitted with a strong piece of tempered spring wire. The first design can be used for any sort of operation where two punches can form the desired shape on the end of the enclosed materials. An example would be a "Core Swage" or "CSW-" die, which takes in a piece of cut lead wire or cast lead pellet (the "core" of a bullet) and gives it a precise diameter with smooth flat ends and extrudes off whatever surplus lead there might be for the weight you desire. Three little bleed holes in the sides of the die, at 120 degree intervals, allow surplus lead to spurt out as tiny wires which are sheared off during ejection. Core swages are used to make the lead filling (core) a precise weight after it has been cast from scrap lead, or cut from a piece of lead wire. This kind of die can also be equipped with a punch having the shape you want for the bullet base, and another punch, at the opposite end, having the shape you want for the nose. Both shapes will be in reverse: the bullet nose is formed in a cavity in the punch, and a hollow base bullet would use a convex or projecting punch. This is what we call a "Lead Semi-Wadcutter" or "LSWC-" type of die. That doesn't mean you have to make a particular shape that you know as a semi-wadcutter bullet; it's just a short-hand way of saying you could do that, or make any other shape that has the entire nose right out to the full bullet diameter formed by pushing the lead into a cavity in the end of the nose forming punch. With most swaging dies, one punch always stays partly inside the die. It slides back until a ledge within the swaging press ram stops it. To eject the bullet out of the die, this punch is pushed forward toward the die mouth. It can be pushed by a pin or knockout bar incorporated in the design of the press (with a Corbin swage press), or it can be pushed by a plunger (with a standard reloading press). We call | |||
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this punch the "Internal Punch" because it always stays in the die. It is "internal" or inside, and never comes out during normal operation. It merely slides up and down, a distance slightly less than the die length, and stops within the die so as to close one end for swaging. It has to move from this position to the die mouth, in order to push out the finished bullet. The other end of the die accepts the material to be swaged. Obviously, that end has to be fitted with a punch that comes out all the way, or there would be no way to put the material inside. The punch which comes out, so you can insert material into the die, is the "External Punch". It is external to the die during the time you are placing the components in the die, and when you move the ram back to eject the bullet. The "Ram" is the moving tubular steel part of the swaging press that holds the die and the internal punch (in any Corbin press). With Corbin swaging presses, the external punch fits into an adjustable "Floating Punch Holder" in the press head or top plate. This assembly is often mistaken for the swage die, because in reloading, a similar-appearing reloading die fits the head of your reloading press. Swaging is "upside-down" from reloading, for reasons that will be clear by the time you finish this book. Again, the steel rods that push the material into the die, and seal the die against all that pressure during swaging, are called "punches". The round cylinder with the hole in it is called the "die". If you fit punches to a particular die, you have just made a "die set", because it is a set of matching parts that work together. You can have several dies and punches in a given set, because all the various dies in that set are designed to work in succession, one after another, to yield a final bullet shape, weight, and construction. The only difference between a "Core Swage" die, which we call a "CSW" die in the language of swaging, and a "LSWC" die, is the use of punches which have the final bullet base and nose shape machined on their ends, and of course the diameter of the die is made to form the final bullet diameter in the LSWC die. Usually the LSWC type of die makes either lead bullets, gas checked, or "Base-Guard" bullets (a superior kind of gas check that scrapes fouling out of your barrel with every shot fired). It isn't used for bullets that have the jacket covering up the bleed holes in the die wall, which includes most jacketed rifle bullet designs. The core swage die generally has flat punch ends and a diameter far less than the final caliber. It is used to prepare the lead core to fit inside a bullet jacket, in most cases (although you don't have to use a jacket—you can just swage the lead core to final shape in the next die if you desire to make a high quality lead bullet, such as a paper-patched or Gase-Guard style). Lead bullets can be made either in one die (the LSWC) or in two dies (the CSW and CS types, or the CSW and PF types). Jacketed bullets generally require at least two and sometimes three or more dies. When we make the die, we need to know what it will be used for. If you say you want a .308 core swage die, you probably do not want the hole to be .308 inches because a core swage has to make a core that fits inside a jacket, and the jacket will usually be about .307 inches on the outside before swaging. The wall thickness of the jacket might be .028 inches at the base, so the core would have to be no larger than .307 minus twice .028 (twice the wall thickness), or .251 inches. | |||
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So, we need to have a sample jacket or at least know what jacket you intend to use, or at the very least to know the diameter you really want for the lead core. If you supply a jacket, or specify one of ours, then we can determine the best core diameter to fit into it. You can cast scrap lead in a core mould, or cut pieces from a spool of .247 inch diameter lead wire to easily drop into this .251 bore die, swage them up to .251 inch diameter, and then they'd fit nicely into the bullet jacket. (There would be two more steps to expand the core inside the jacket, blowing the jacket out like the skin of a balloon, and then forming the ogive on the bullet to finish it). But if you wanted to make a lead .308 diameter bullet for a .30 Mauser pistol, then we'd make almost the same kind of die but we'd make it with a bore of .308 inches, and fit it with the right kind of nose and base punches. So you see that even if the dies look similar and work in a similar way, their purpose really makes them different dies. That's why we need two different names for them. It helps avoid a lot of unnecessary explanation and errors. Perhaps you might order a .308 LSWC die, maybe with an "Auto-loader" nose and a "Cup Base". We would use the short-hand "AL" for Auto-loader, a sort of rounded semi-wadcutter shape, and "CB" for Cup Base, which is a shallow concave base form. To us, the term "semi-wadcutter" is a general description for a bullet style that can be made using a punch to form the nose, instead of a point forming die. The Target Wadcutter, Button-Nose Wadcutter, Keith, Auto-Loader, and even round nose SWC styles are all subsets of the semi-wadcutter group, since every one of these styles is made in the same die just by changing the nose punch. Two other kinds of dies that are made with a straight hole and two full-diameter punches are the "Lead Tip" die and the "Core Seat" die. These don't have any bleed holes around their middle. The core seat die is also called a "Core Seater" and abbreviated "CS". The lead tip die is also called a "Lead Tip Former" and is abbreviated "LT". It is not the same thing as a point former or "PF" die. The purpose of a core seat die is to expand the jacket, which is made slightly less than final diameter, and at the same time achieve a very tight fit between the core and jacket. You can use either a punch that fits into the jacket, to make open tip style bullets, or you can use a punch that fits the die bore, and thus make large lead tips. The use of a CS die to make lead bullets (after first swaging the lead core to exact weight in the CSW die) is a perfectionist's way to build lead wadcutter or semi-wadcutter bullets: it can be more precise because you separate the pressure needed to extrude surplus lead from the pressure required to form the edges of the bullet nose and base. In a LSWC die, the pressure stops building when the lead begins to extrude through the bleed holes. Thus, some shapes of bullets with deep nose cavities or hollow bases and sharp edges may not receive enough pressure to fully take on the exact punch shape, if that pressure is higher than the pressure which causes lead to spurt out the bleed holes. By first using a CSW die to adjust the weight, and then using a separate CS die to form the nose and base, the pressure issue is resolved for all shapes and styles. | |||
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A punch with a cavity in the end makes the bullet with a semi-wadcutter shoulder (the edge of the punch must be in the neighborhood of .02 inches thick in order to stand the high swaging pressures). A core seating punch with a projection on the end, usually conical, makes a hollow point cavity in the lead core. Of course, you can use flat, domed, slightly convex, or highly pointed punch shapes to suit your desires, and make virtually any kind of base you want just by changing the punch. Often this will be the internal punch, but you can have the die built with the base punch being external if you wish. The reason we normally make the nose punch external to the die is because usually people change the nose shape much more often than the base, and it is easier to change the external punch in seconds without removing the die from the press ram. Technically it would not matter which punch made the nose and which made the base. The purpose of the lead tip forming die is to finish the very end of a pointed (spitzer) bullet, and it isn't normally used for semi-wadcutter or large lead tip bullets. It looks just like a core seater, but the bore diameter is slightly larger than the final bullet size, whereas the core seater diameter is just slightly smaller than final bullet size. The internal punch of a lead tip die is designed with a cavity to reshape the extruded lead tip of a sharp-pointed rifle bullet so that it looks perfect. It cannot form the entire ogive because the edge of the punch, which must withstand tons of swaging pressure, cannot be paper-thin and survive.
We started this section talking about two general die designs, one with a straight hole through it, and one with a semi-blind hole. This second kind of die came about because, try as you will, there isn't a reliable way to make a straight-hole die form a smooth curve from shank to tip. (The bullet nose curve is called the "ogive", pronounced OH-jive, and comes from the French ogee which is the bullet shaped curve over a doorway). That punch with the cavity machined in the end must have some thickness at the edge, and this edge will impress itself on the bullet to make a shoulder. There's even more to it than that: if you try to push a jacket into the cavity in the punch, the edge of the jacket will strike the edge of the punch. It won't reliably jump over that edge, but instead either the jacket or the punch will be crumpled up. In Corbin dies, the jacket is far weaker than the punch, so it folds up. So, that leaves the problem of how to make a typical rifle-style bullet, or a smooth rounded or angled bullet nose of any type, not having a lead tip from where the jacket stops to the end of the bullet. The semi-blind hole die is used whenever the nose or base of the bullet has to turn inward, away from full bore diameter, without a shoulder or step. Conventional rifle bullets, boattail bullets, and modern jacketed handgun bullets with the jacket curving or angling smoothly inward from the shank to the ogive all require the use of this die design. By "semi-blind hole", I mean that the hole in the die is not straight through the die, but is shaped like the bullet itself. At the tip is a very small punch to push the bullet out by its nose, and this punch is retracted a short way up into its little | |||
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access hole so there is no possibility of the bullet material pressing against it (which might otherwise bend the small diameter punch under those tons of pressure). The "Point Forming" die, which we abbreviate "PF", accepts either a lead core, or the seated lead core and jacket combination swaged in the core seat die. A full-diameter external punch shoves the material into the point forming die. The material is compressed inward in the small end of the die, giving the bullet its smooth curve or angled nose (the ogive). The pressure also expands the shank slightly to final diameter. The bullet material follows the die wall, right up to the ejection pin hole and into it, if you push too far. This would put a little parallel "pipe" on the tip of the bullet, which means you need to back off the depth adjustment (the punch holder) just a little. The smallest tip which you can put on the bullet using the PF die is the diameter of the ejection pin. The smallest ejection pin that can be used is one that will withstand the ejection pressure without bending. If you happen to forget to apply swaging lubricant, or if the jacket is larger than the die cavity diameter, the pressure required to eject the bullet can go considerably higher than the design parameters. This means that the ejection pin needs a little extra diameter as a safety margin. A typical ejection pin (the internal punch for a point forming die is usually called an ejection pin) for .224 or .243 caliber might be in the .062 to .081 inch diameter range, depending on the expected ejection pressures and the abuse expected for the die. Dies made for professional bullet makers, who know how to stop short of bending the punch if anything goes wrong and who won't be upset if they do need to replace the ejection pin now and then, might tend to be closer to .062 inch; dies made for experimenters who will be exceeding the design limits frequently tend to have larger ejection pins, as do dies made especially for lead tip bullets. If you make a round nose bullet, a truncated conical pistol bullet, or even a flat tip rifle bullet in the PF die, it works very nicely for either open tip or lead tip, depending on how much lead you put into the jacket. If you make a bullet with the jacket curved around to the diameter of the ejection pin, then the pin will press down against the end of the jacket and push the bullet out of a well-finished, diamond-lapped swage die with relatively low force. But if you want a small, sharp or rounded lead tip, the ejection pin spoils your plan by making its own flat circle on the very tip of the bullet. To form a small lead tip on the bullet, you would need to leave a little extra lead projecting from the end, which the ejection pin will deform somewhat during ejection, and then use a "lead tip forming" die, or "LT" die, to shape up any extra lead. The lead tip die accepts the nearly-completed bullet from a point form die, so it has a bore diameter slightly larger than the finished bullet size. This works only because the pressure needed to shape the lead tip is so low that the bullet shank will not expand. In fact, since the lead tip die is just minutely larger than the point forming die, perhaps only .0005 inches, it can assure that the bullets will be more parallel and have almost no "pressure ring" at the base. | |||
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The internal punch of the lead tip die has a cavity that is shaped not exactly to the same outline as the bullet ogive, but with a slightly shorter radius. For instance, if the bullet had an 8-S ogive (we'll explain this in detail later, but the ogive radius is the length of the radius used to swing the arc that gives the bullet ogive its shape), the radius of the cavity shape inside the lead tip forming punch would be perhaps 7S. That is a shorter radius. The result is that the lead tip is formed and the surplus lead pushed down at a slight shear angle between the wall of the punch and the ogive of the bullet. If you leave the right amount of exposed lead, the punch will form a neat lead tip with a very slightly different ogive curve from the rest of the bullet. If the punch shape were made precisely the same as the point forming die, the edge of the punch would strike the ogive of the bullet and create a ring, instead of neatly reshaping the tip. Bear in mind that the LT die is not used by itself, nor is it used instead of a PF die. If you use one at all, it would be to follow a point forming die. Remember, the jacket edge won't jump over the punch edge. If you already have a curved jacket, from the PF die, then the edge will slip past the cavity and let you shape the lead tip. A LT die can also be used, in some cases, to help close the open tip of a jacketed bullet more tightly than could be done in the PF die alone. With care, a bullet maker can learn to push the open end of the jacket nearly closed, by gently using trial and error adjustment of the punch holder. Not every ogive shape or design lends itself well to this operation, but enough of them do so that it is worth mentioning. Rebated BoattailsWhat about bevel bases or boattail bullets? Those also have the bullet smoothly angled away from full shank diameter. So, they also require a variety of the point forming die which is used to shape the base instead of the nose. The boattail bullet has largely been replaced in swaging circles by the superior "rebated" boattail, abbreviated "RBT" as opposed to the more conventional "BT" for boattail. Why are most custom bullet makers using the RBT instead of the standard boattail base? There are three reasons:
1) A regular boattail bullet tends to act like the focusing nozzle of a water hose during the moment it emerges from the barrel. Hot powder gas rushes around that boattail angle, flow up the sides of the bullet, and continue in a smooth, laminar low pattern right around the front, where they break up into turbulent flow and make a fireball of gas—right in the path of the bullet! You can get up to 15% increased dispersion at the target just from the buffeting the bullet gets by shooting through this ball of gas. A flat base bullet deflects most of the gas in a circle of fire, expanding rapidly out from the bore with a clear space directly in front of the bullet. The edge of the flat base acts like a "spoiler" to break up the | |||
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laminar flow before it can get started. And so does the sharp shoulder on a rebated boattail! How does a 15% improvement in accuracy sound as a benefit of using the RBT design?
2) The boattail bullet tends toward more bore erosion than the rebated boattail, because gas pressure on the boattail tends to peel it back away from the bore and let some gas up past the bottoms of the rifling grooves, where it cuts the bullet and the barrel like a hot cutting torch. The rebated boattail has a 90 degree shoulder that takes the pressure parallel to the bore, instead of at a compression angle away from it. How does increased barrel life strike you as a second reason for using RBT bullets instead of the regular BT style?
3) The tooling lasts longer, costs less to build, and is more easily built to high standards of precision. Corbin Manufacturing has perfected a method of using two dies, which we call the "Boattail 1" and the "Boattail 2" dies, as a set, to produce a virtually flawless and highly repeatable rebated boattail. Instead of making the boattail angle so it can be higher on one side or at a little slope like some of the factory production you see today, this system guarantees that the boattail will start precisely at the same point on one side of the bullet as it does on the other, every time.
With all these benefits, there is hardly any reason to make standard boattail dies these days. The RBT has been proving itself all over the world for more than 30 years to those who are wise enough to give it attention. However, if you were to ask what base design I would generally recommend for jacketed bullets up to 250 yard range, I would be unhesitating in saying a flat base. Rebated or not, a boattail does not give you superior accuracy in and of itself. It gives you less base drag. Whether or not that translates into better accuracy than a flat base hinges on whether the increased drop or higher trajectory arc gives you any problem hitting your target, and whether there is much cross wind to push the bullet off course. Usually at subsonic velocities, the rebated boattail gives you a much greater benefit in comparison to other drag factors, than it does at Mach I and above. The shock wave causes far more percentage of total drag at supersonic velocities, so making the nose more pointed produces more effect than streamlining the base. The best silenced, subsonic bullets for special ops have been rebated boattails with a blunt round nose (and other special features for expansion). Bevel BasesBevel base bullets are made by seating the core in a special "point forming" die instead of the usual core seating die. The jacket is put into the die, and the lead is pushed into the jacket. The base of the bullet flows down into the short, beveled section of the die (it can't be a punch cavity, remember, because the edge of the | |||
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punch would cut the bottom of the jacket). You could also seat the bullet in a normal core seating die, and then reform the base in this die, but it would be redundant. A lead bevel base bullet could be made in two steps: swage the lead core using a rather large, almost finished diameter core swage, and then push the bullet into the special point forming die backward, using a nose punch as the external punch. Come to think of it, any lead bullet with a smooth ogive (no semi-wadcutter shoulder) can best be made by using first a CSW die to adjust the weight, and then a PF die to form the ogive. Without a jacket, you don't need the CS die, the purpose of which is to expand the core into the jacket and form a tight, parallel shank. Dies Classified by Press TypeWe've talked about the basic design of bullet swage dies, in regard to their function. There is another category for classification of swage dies, and that is by the kind of press used to operate them. Swaging dies can be designed to operate in a reloading press (with severe limitations on pressure and precision), or in a number of different models of bullet swaging presses, both hand and hydraulic-electric powered. Years ago, we worked out a system of making standard parts for dies that would cover a wide range of calibers, and thus cut the cost of swaging through efficient use of what I call "semi-custom production". We designed presses and die sets so that we could build similar punch and die blanks for certain ranges of calibers and bullet lengths, and then choose among perhaps three die body lengths for every caliber from .12 to .458 in the hand presses, or from .224 to .998-in the dies for our big hydraulic presses. We didn't have to design and build each die from scratch, because we built a standardized system for determining the minimum requirements of strength, die length, stroke length, punch geometry and strength, steels and heat treatment. We could run hundreds of blanks for each of the various presses, then hand-finish the cavities and hone the rough-finished punch blanks to a perfect fit during the custom phase of each order. It combined the economy of mass production with the flexibility and precision of custom tooling. Corbin swaging dies are up to ten times less costly than competitive dies without any sacrifice in precision because of this semi-custom production technique, and the fact that we design and build several different presses to take full advantage of the kind of operations you might want to undertake. The classification by press type also defines the die thread and diameter. The last letter in the catalog number identifies this classification. Dies with a catalog number ending in -R (such as the PRO-1-R) fit a standard 7/8-14 thread reloading press with an RCBS-type button shell holder ram. The die screws into the press head like a reloading die. The external punch slips into the T-slot of the ram. You do not also use a shell holder, since the punch base is made to simulate one. Dies with a catalog number ending in -M fit either the discontinued Silver Press, or the current S-Press. They are being phased out of stocking status in favor of the -S dies, which are larger and stronger, and fit the current S-Press or its | |||
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predecessor, the Series II press (discontinued). However, we will continue to make them on special order, just not as a stock item. The -M dies have a 3/4-inch diameter main body, a thrust-adsorbing shoulder, and a 5/8-24 threaded tenon. The die screws directly into the press ram, and the external punch is held in a Corbin floating punch holder in the press head. An example of an -M type die is the LSWC-1-M, a lead semi-wadcutter die. The current type -S dies fit the discontinued Series II press or its replacement, the S-Press (Catalog number CSP-1). An example of a set of -S dies is the FJFB-3-S, a three-die set. The -S dies have a longer and larger diameter body than the -M type, being 1-inch diameter. By using the same 5/8-24 threaded tenon, the thrust shoulder is wider and thus spreads the force over a wider area (the top of the industrial chromed alloy steel ram in Corbin presses). This also means the S-Press can accept both the older -M dies and the current -S dies. A bench-type hydraulic powered version of the S-Press, called the "Hydro-Mite", also uses these -S dies. Finally, the type -H dies are made to fit the Corbin Hydro-Press, Mega-Mite hand press, and Hydro Junior press. These dies are typically made in a 1.50 inch diameter, with a length appropriate to the maximum bullet weight to be produced (up to three inches). The thread tenon is made with a 1-inch 12 thread (meaning 12 turns per inch) to screw directly into the press ram. The external punch fits into the huge FPH-1-H floating punch holder, in the press head. A "positive stop" FPH-2-H punch holder is also available for extreme high precision weight control. Dies for Other PressesSpecial diameters of dies can be built to order, either to fit Corbin presses or other presses. Diameters of up to four inches with nearly any desired thread can be made. Usually it is best to use a standard die that fits one of the Corbin presses, rather than to spend very much on custom work to fit some other press. In the first place, the cost of special replacements and additions can quickly use up any savings in using an existing press versus buying a standard swaging press. Often I have heard "I already have a press that I want to use" and the meaning is, "I don't want to spend money for another press." I agree, and would do the same, but only if the cost of building the custom dies and punches and making them work in this nonstandard press (for swaging purposes) is still less than just buying a regular swaging press. Often it costs more to fiddle around with special jobs than it does just to buy a standard swaging press. And then, from that point on, you don't have to worry about any special replacement parts, or additions that also have to be custom made (meaning both fairly long production delays and additional cost). Usually, the design of a swaging press gives you a big advantage in speed, accuracy, and safety over using other kinds of presses. After all, a pants press, a wine press, a full court press, and a printing press all are variations on the term "press", and they are not suitable for reloading. Having said this, it is still possible to have custom dies built for just about any press you own. Just bear in mind that there is time involved in making working drawings, checking the stroke and ejection position, getting special thread taps and dies (sometimes), setting up the tool | |||
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ing for a onetime job, and other costs that have long been amortized over thousands of dies when you choose a standard production design instead. Besides, we may have spent a couple of decades and tens of thousands of dollars in testing and improving our standard tools and presses. Building something for the first time in a different design often requires some investment in development, which may be a waste of your money if we've already done it a thousand times before in a different and better system, which would be yours if you just got the right platform to run it (the proper press). With a different, special tool, you get to pay for any unforseen development requirements. With our own products, we already paid for development and you get to benefit from that. It's usually a better deal. Swaging Principles1. Always swage "up", never "down". Swaging down is a contradiction. You "draw" down, by pushing something through an open ended ring die, like our JRD-1 jacket drawing die, or BRD-1 bullet reducing die. Drawing makes the part smaller in diameter and longer. It can also cause separation of the core and jacket if done to excess. Swaging makes the part shorter and larger, and tightens the grip of the jacket on the core. 2. Pay attention to the instructions. If there are special written notes with your die, they are important because they modify or improve the general instructions and replace them. If there is a difference between specific notes sent with your set of dies, and anything published in general (as in this book or in general printed literature), follow the special written instructions in any respect where they may differ. Swaging is partly an art, and various materials or sizes may react differently to the same general kind of operations. 3. Use the right terminology! I cannot stress enough how important it can be to read what you have before you start to use it, and order the right part numbers and names of parts. People call the external punch everything from a "pin" to a "ram" to a "die" to a "die punch". How are we supposed to know what you mean? If you order it wrong, you get to pay a restocking fee or, if it is custom made for you, then it may not be returnable. A die is the vessel or cylinder that holds the material. A punch fits into the end of the die and pushes on the material. A "pin" is part of the pivot system of the press, or the wire ejection pin that fits into a point forming punch. A "ram" is the moving steel drive component of your press into which the swage die screws. There is no such thing as a "die-punch" or a "punch-die": putting terms together to suit yourself just confuses everyone. 4. Use the right materials! A set of dies made for a specific jacket, a certain lead hardness, or a certain alloy and size of copper tubing, may be able to work with other materials but probably not without adjustments to the punch and/or die dimensions and possibly not without developing differences in technique. Nearly all problems with broken dies and stuck parts or improper sizes comes from the use of materials other than those we used to develop the tools. Hardness, grain and dimensions make a huge difference in your success. | |||
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3. Bullet Swaging SecretsBefore I start telling you about the various kinds of swaging presses and dies that work with them, and why you might want to select a given type of press and die for a certain kind of bullet making, it would be useful for you to know some facts that have taken decades to figure out, and which most of the people who have figured them out wish to keep from you, since it might affect their own income if you knew. If you don't care to wade around in the backwaters of history, skip this chapter and go on to the "How To" chapters that follow. It isn't absolutely necessary to be aware of all the misconceptions, phony physics, and junk science that is tossed about as if it were gospel. A lot of people make a good living based on these misconceptions, whether on purpose or because they believe it too, and it is not helping them a bit if you become aware of the errors in thinking that make this possible. But I suppose someone has to support those people: you can, if you wish! The Myth of ExclusionThe most common misconception about bullet swaging is that only a few people really have the money and expertise to do it right—that equipment to make a good bullet is far too costly for you to buy, and the techniques are filled with "secrets" that only a few bullet-makers are smart enough to understand. In other words, stay away from swaging because (1) you are not smart enough and (2) you cannot afford the right equipment. Leave it to the "experts" who know best, in other words... the same "experts" who are eager to tell you this, and to scoff when you mention that you might have found a way to try it yourself. The reason this myth is repeated in print every year is simple. Think about it: if you were making a reasonably good income from selling your own custom swaged bullets and someone asked you to tell a magazine audience all about your business, would you tell them "It's easy: anybody can do it with a little reading and a few hours of experimenting with moderately priced equipment!" Or, would you be more likely to think about it and then say "Man, it's hard: the only equipment that works costs thousands of dollars and takes years to figure out. You guys are way better off just to pay me to do it for you and keep on buying my bullets!"? Always remember to consider the source when you read anything, and follow the money trail. (Yes, I'm aware of the irony, but you already bought this book so I can afford to be honest in the writing of it!) It works in almost everything in life, not just bullet swaging. Before you read something, try to figure out who wrote it, who pays them, and why they might be influenced in their comments and opinions by the source of their income. | |||
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It's not a conspiracy: it's just how life works. Everyone has an interest in protecting their source of income. The more unusual the occupation, the less likely it is that the person will say anything that would encourage you to go into competition. Successful people learn early how to get good information from shaded stories without necessarily accepting everything at face value. All this means is that when you read articles by or about bullet makers or their products, be aware that the products were made by human beings, not mythological Titans. Odds are pretty good that, given the right equipment and information, you could do the same thing. Or maybe, even better. The Myth of the ShortcutIn a long and largely successful business career, I've found that the only reliable income is that generated from trading good information, services and products. Perhaps some have become wealthy by chance, or by trickery, or by other transient opportunities, but by and large what works is providing consistent good value. The surprise is that so many people think otherwise, and spend their lives looking for shortcuts. So much effort is expended in the search to avoid putting out any effort! It isn't fast or easy to build a reputation for good value, but the alternatives are too unreliable, even putting moral considerations aside. This myth isn't just for bullet makers, but it seems to come up frequently in discussing a new bullet business with someone who wants to make back his investment in a hurry. "What's the hot item to make? What would make the most money in the shortest time?" Well, here is where I could take a shortcut myself and make up some foolishness that would insure a quick or bigger sale. I could speak eloquently about whatever this client was sure to have seen on the covers of the latest gun magazines, and it would be easy to make a good case for whatever caliber, style, or gun was featured as the magic carpet one could ride to riches by making that particular bullet, or one for that particular gun. But unless it was true, I wouldn't do it, and while there is some truth to the idea of following the latest trends, it isn't likely to result in immediate riches. There are not enough potential bullet makers to treat clients like used car buyers, even if I could somehow justify acting that way. Either my clients have to be successful, and continue to purchase equipment and supplies as they grow, or the swage die business will not work well enough to be viable. After more than three decades of providing income for six families of Corbin employees, it's fairly obvious that there must be something reliable and long-term behind the ideas I am discussing here. It's not very likely that thousands of handloaders would come back, year after year, for products and ideas that didn't meet or exceed their expectations. Many people do, in fact, make a good living using Corbin equipment to produce high quality custom bullets for other shooters. You see their ads every time you pick up a gun magazine. They start small, often just as a hobby, and their interest and business grows and expands to other equipment, which Corbin de | |||
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signs and manufactures. Our design and engineering work, as well as marketing help, is critical to the success of most of our clients (there are some who had everything figured out from the start, but not many). Because a substantial part of our income and reason for our own success has been based on appropriate advice and honest dealing with our clients, your trust is a critical factor in Corbin's very existence. We continue to have backlogs for our work primarily because people know that they can trust in the essential facts that are spelled out in our books. The myth that you can get there by some shortcut inspires countless other people to try, year after year, making a brief appearance and then disappearing forever. In their wake are abandoned and disgruntled would-be bullet makers, who may get such a bad taste for swaging from the experience that they never want to try it again. That is, of course, my main worry from a business point of view. It doesn't take too many shortcut takers to spread a bad feeling about what can be a marvelous technology when done correctly with well-made tools. Shortcuts are what allows equipment to be made more cheaply, by using cheaper materials, taking less time to fit and finish the components, or skipping most of the tests and rework that might be necessary if a reasonable quality control procedure was in use. But a bullet-maker could forget the reason cheap copies of good equipment are cheaper, and think all such equipment is equally flawed. The same myth can affect the bullet-maker, even when he is wise enough to purchase good equipment. Taking shortcuts in the process of making bullets, in order to make them faster, can result in less satisfactory bullets. The custom bullet market is not interested in cheap bullets: it exists because of the need for bullets of superior performance. Today, you can hardly pick up a gun magazine without reading something about one of my clients who makes a better custom bullet. Custom bullet making has been elevated by these people from a dark art to a serious, mainstream part of the firearms industry. But these bullet-makers, by and large, did not take shortcuts. They spent an average of 18 months building up to the point where they could show a profit. Some did it in less than a year, others took two or more years. They built a business, they didn't trick one into existence. You might not care at all about the commercial possibilities for custom bullet making, but it affects you anyway. The mass producers have been forced to come up with their own premium lines of bullets and have often purchased bullets from my clients instead of trying to come up with their own. The fact that hundreds have turned to bullet swaging as a way to make a living, and thousands more use it as a way to make a little spare cash on a part-time basis, means that your bullet selection has improved vastly in the past few years. Guns of a type that you might not have considered using for defense twenty years ago can now be put into service, since the bullets have improved their performance so much. Game animals that you might have wounded and lost twenty years ago can be cleanly taken without the suffering and without the long hikes to the bottom of canyons where the game was able to run and finally die a lingering death because of poor bullet performance. Hunting is more humane when the bullets perform flawlessly on the first shot. | |||
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Your scores at benchrest, metallic silhouette, IPSIC, and even blackpowder matches can be higher than they were "back then" because of the tremendous amount of research and testing done by all the custom bullet-makers. Laws have been passed or modified based on certain kinds of custom swaged bullets that did not come from any mass producer. If you don't think you have some interest in commercial swaging already, think again! None of this happened by taking shortcuts, either in the making of the equipment, or in the using of it. The Myth of CarbideThere is a great deal of emphasis placed on the buzzword "carbide" at this time. Carbide is a rather generic term that covers a lot of ground, rather like the word "chlorophyll" back in the 1960's, or any other semi-technical term that is turned into an advertising catchword. There is no such thing as a single kind of die material called "carbide", except in the minds of ad writers. When you heat any tool steel to a high enough temperature, some of the carbon in the material dissolves in the nearby iron, and forms a ferric carbide material which can be captured in the frozen matrix of the steel if the temperature is lowered quickly enough. The ferric carbide trapped in the steel mixture is primarily what gives the steel its hardness. The structure also has a matrix of iron and other elements, which form complex compounds that give the steel ductility, ability to remain hard at higher temperatures, corrosion and shock resistance. All hardened steels have "carbide" in them: that's what makes them hard. If you systematically reduced the amount of iron and increased the amount of carbon that dissolved in the iron that was left, you would wind up with a very hard, but also very brittle material. It might be almost "solid carbide" but it wouldn't be very strong. By forming compounds of tungsten and other metals with carbon, the General Electric company (and others) developed commercially acceptable variations of "carbide" in a wide variety of grades. General Electric's trade name of "Carboloy" was applied to some of these. The important thing to note is that there are variations that are nearly as soft as hardened tool steel, and others that are so brittle that they shatter like glass if force is applied incorrectly. Some carbide materials can handle high temperatures and some fracture when heated and cooled during use. Some make good tool bits, and some are only good for a thin coating on the surface of a hardened steel bit. Some are reasonable to machine accurately, and some cost a fortune to machine compared to making the same shape from a good tool steel. If you were to be faced with the decision of a material from which to build dies for a high speed punch press, working at 40 strokes per minute or more, and making several million bullets, then one of these grades of carbide material could give you higher temperature operation and thus longer life than a tool steel die. Because the harder materials are more abrasion resistant, you would be able to run the dies for a longer time before replacing them. | |||
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They would still need to be lubricated: the idea that carbide dies need no lubrication is foolish. It is like saying that because your car engine might run 100,000 miles without changing the oil, you don't need to change the oil. It might run 250,000 miles if you did! It is necessary to consider value to make a good decision about die materials. Value is the cost of the die amortized over the number of bullets you expect to make, considering the amount of wear which will take place before the bullets are no longer acceptable quality. It is somewhat subjective, since one person might consider a die "worn out" when the bullet diameter increased by 0.001 inches, and another might find that the 0.3090 bullet shot even better than the standard 0.3080 in his gun. The point where you no longer consider the bullet diameter acceptable determines the life of the die, for your application. Wear is related to heat and abrasion. If you operate your dies in a hand-fed system of any type, it will be impossible to make more than five or six bullets a minute. At those stroke rates, any heat from friction would dissipate into the air before the next stroke. There would be minimal heat buildup, so that normal swaging lubricant (Corbin Swage Lube) would be sufficient to protect the die and the components from frictional abrasion not caused by dirty components or by polishing compounds embedded in the jacket material. In a power-fed system, it is possible to stroke the press so fast that heat cannot radiate away into the air as quickly as it is generated, until the die becomes quite warm. It reaches a stable high temperature by radiating heat into the air, and into the frame of the press. Swaging lubricants may not stand this high temperature, so the metal surface needs to be made of something that will remain hard and resist abrasion without as much lubrication. Certain grades of carbides will handle the job. Value is indicated by first estimating the tolerances which are acceptable for the bullets, and then figuring out how long a set of dies will give that range of tolerances, and how many bullets are made with each set, for what price. The lowest cost per bullet indicates the best value, all other things being equal. In the high speed punch press, a set of dies might easily cost $3000. They might slowly wear to an unacceptable tolerance after two million bullets were made, at a cost per bullet of three thousand dollars divided by two million bullets. This is a cost of 0.15 cents (not fifteen cents, but fifteen hundredths of a cent) per bullet. In this kind of operation, properly made tool steel dies might only last 50,000 bullets, at a cost of about $300 for the dies. That is 0.60 cents (sixty hundreds of a cent) per bullet. Obviously, the value is four times greater for using the carbide dies in this application. One might reasonably expect to make two million bullets on a punch press system: at 40 strokes a minute, and a bullet per stroke, that is only about 104.167 days or about 3.5 months—assuming the punch press is run eight hours a day, which isn't unreasonable. But even the largest and most successful custom bullet maker seldom turns to punch presses. The average custom bullet operation (if one could ever say these outstanding operations are anything close to "average") turns out about 50,000 bullets a year. After all, the market is limited and the price is fairly high (worth it, | |||
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but not cheap). You probably wouldn't make one million bullets in a lifetime of hand swaging. If you could make two bullets a minute, and worked at it every weekend for four hours, you'd only be making 24,960 bullets a year. When run at less than ten strokes a minute with proper lubrication, the high-carbide content die steels used by Corbin hold acceptable tolerances for at least 500,000 bullets, and some have made over 1,500,000 bullets in commercial operations started years ago. Assuming the dies would make 500,000 bullets, this means your $300 investment in dies would last for over 20 years if you made two bullets a minute, working every weekend for four hours, every week of those years. If you are just now turning 20 years old, you'd be 40 before you needed to buy another set at that rate. If you expected to live to be 100 years old, you would have a lifetime of bullet making on just three sets of dies, for a total cost of $900. Now, most people don't make anywhere near 24,960 bullets a year unless they are in business to make bullets. The odds are great you'd never make 500,000 bullets in a lifetime. But just suppose you did. Your cost per bullet for determining die value would be $300 divided by 500,000 bullets, or .06 cents (six hundredths of a cent) per bullet. In your lifetime, if you made 1.5 million bullets, you'd use up three sets of dies, so your total cost per bullet would be $900 divided by 1.5 million bullets, or .06 cents. This is for using tool steel dies. If you purchased $3000 carbide dies, you would not get one bit more accuracy or any better die, other than the fact that long-term abrasion resistance would be less, so you could get by with one set of dies for your lifetime. We assumed you might live 100 years, and make 1.5 million bullets. Your cost per bullet with a carbide die set would be .20 cents per bullet ($3000 divided by 1.5 million bullets). The steel dies are three and a third times better value for this application! That is 333% more value for your money with the steel dies. The reason I've gone so long into this is not any animosity toward "carbide", but because of the widely-held perception that just stamping the word "carbide" on a die automatically blesses the product with supernatural powers and makes it somehow more accurate. A die is only as accurate as you can make the hole. It is a lot easier to make a good die from a material that can be worked in its annealed state, then hardened and given its final adjustment in size with diamond lapping in the hard state. The easier a job is to do, the less it has to cost. So, you get more value: the same accuracy for far less money. Obviously, it is much easier to promote the myth, than to explain the facts. Advertising is sold by the column inch or fractional page, or by the word...and it costs a lot more to educate than to dazzle the reader. Fortunately, a book has plenty of space for education and you've chosen that path rather than just allowing yourself to be dazzled. Following the "carbide worship" path, the term "ECM" or "EDM" sometimes is waved about as a sort of accuracy magic wand. The terms refer to "electrochemical machining" or "elecrical-discharge machining". ECM is a form of "reverse plating" where metal is removed from the surface of the work by a strong flow of | |||
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electricity through a conductive electrolyte solution. EDM is a form of "spark erosion" where an arc burns away tiny pits in the surface and eventually removes it in a controlled manner, often under an insulating solution that carries away the eroded metal. Electrochemical machining is a last resort, not a step up. It is used when there is no other practical way to machine a part, because it is very costly, slow and difficult to make the hole precisely the right diameter and shape without going to much higher expense than with traditional machining techniques. ECM has its uses, one of which is to machine carbide materials that simply cannot be cut any other way. There is nothing inherently more accurate about ECM. It costs fortunes in equipment just to make it the same accuracy as lathe boring, reaming, and diamond lapping. Using ECM makes sense when you can't cut the material in a more traditional way. People who sell ECM machines are the first to tell you this. There is nothing inherently "more accurate" in using electrical machining as opposed to diamond lapping. Thin, fragile sheets of metal or brittle, hard carbide materials are best machined by ECM, but materials which can be machined with a faster traditional method should be. One who simply swallows the advertising hype is set up to spend extra money without getting the extra value. If I thought that there was better value for my clients in selling them $3000 dies, I'd certainly have no reason NOT to do it! I'd rather get ten times as much for a set of dies, if I could justify it to myself and to my customers. But for the past 30 years I've been proving over and over that it isn't good value for this application. What, exactly, is the benefit, other than making more money for me? I'll just have to rely on the good judgement of ten more handloaders, instead, to make the same amount! The Myth of Equating BC with AccuracyAnother myth is that aerodynamic shape is synonymous with accuracy. Years ago, I made some bullets that were just cylinders without any ogive at all, and fired them from a benchrest rifle in .224 caliber into a group that measured about 0.2 inches center to center. Then I fired another group made with 6-caliber ogive spitzer bullets made exactly the same way, with the same weight and diameter and the same materials. These made almost exactly the same size group. The gun was at its limit and the bullet shape had no effect on accuracy, except that the cylinders landed a little lower on the target (more drag, so they dropped slightly more). In our work for various government agencies, Corbin made dies that we called the "Ultra Low Drag" or "ULD" design, many years before the popularity of the so-called "VLD" design of the late 1990's. The two designs are quite similar. In fact, nearly all low drag designs that are practical utilize a long ogive and some kind of boattail. Ours used a nine-degree rebated boattail, and a 14-caliber radius curve that was offset by 0.014 inches from the tangent (a secant ogive, in other words). There is nothing magical about the numbers. There are dozens of variations which would work approximately as well, better in some guns, worse in others. | |||
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There is a problem with promoting these buzzword designs: people tend to believe that they solve all problems of accuracy, when in reality they are very special designs made for certain kinds of loads, rifling twist rates, and purposes. They are not always more accurate nor are they even useful in some guns. Here are some of the problems with the very low and ultra low drag designs (which means "high BC", the ballistic coefficient): To offer less air resistance, the bullet needs to be more streamlined, which in turn makes it longer for the same weight, or lighter for the same length as a conventional design. To keep the amount of shank in approximate balance with the extra long nose (which would fill up with all the available lead in a normal or light weight design and leave nothing for the shank), these bullets are usually made in the heavier weights for the caliber. This means that the long, heavy bullet has the center of balance shifted toward the rear, so it wants to turn over more easily than the conventional bullet, and thus requires a higher twist rate to stay nose first. If you have a barrel with the appropriate faster twist, you may get a flatter shooting bullet with equivalent accuracy to a normal design. Since the custom swaged bullets are usually made with more care than mass produced bullets, you may even get superior accuracy plus a flatter trajectory. But if you don't have a faster twist rate, you may find accuracy actually is worse than that of a shorter bullet having lower BC. The longer ogive and boattail (or rebated boattail) combine to make the same weight of bullet longer than in a conventional shape, which means that the bullet may not chamber or feed in some guns, and may actually be too long for the throat in the barrel. This might require setting the base of the bullet far down into the cartridge, intruding into the powder space, and possibly requiring the case neck to be partly encircling the start of the ogive. This means the bullet may not be held securely on a center line with the cartridge, but instead might be able to tip and start into the rifling at a slight angle, which does no good for accuracy. Bullet jackets need to be longer for the same weight, since the long thin nose doesn't hold as much volume (and thus weight) as a more rounded shape. And if you wish to make a light weight bullet, you'll need to use low density core material such as Corbin bullet balls, because if you fill the long ogive with lead, you'll need to at least balance the nose with a reasonable shank length. Having a long nose and balancing it with the shank means the minimum weight is higher than with a more rounded nose. In other words, you trade a somewhat flatter shooting bullet design for versatility in range of weight. A more traditional 6-S ogive or a round nosed shape will give you both heavier and lighter weight possibilities. On the other hand, extremely efficient airframes do give you a flatter shooting bullet, because they drop less in the same amount of flight time. While less trajectory isn't necessarily the same as more accuracy, it contributes to your ability to judge distance and hold the sights in the right place. It helps you be a better shooter, rather than actually improving the accuracy of the bullet, but the effect is the same. My point is that if you use accuracy and flat shooting as synonyms, you'll be just far enough off the mark so that you'll fall for some of the advertising hype about bullet shape. You may be like the fellow who heard that three of the top | |||
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benchrest shooters won that year using bullets that happened to have a 7-S ogive (a nose shape formed by a curve that has a radius of seven calibers) instead of the more common 6-S, so he passed up good buys on both 6-S and 8-S ogive die sets to wait for a custom made 7-S set. In truth, any of those sets would have been fine, and the 8-S would be slightly flatter shooting yet.
I'd like to let you in on another secret: there is no inherent difference in accuracy between spire points, truncated conical points, round noses, spitzers, and secant ogives, if you make all of them from equal quality materials with the same level of care. A round nose or what we would call a 3/4-E (elliptical ogive with a length of 0.75 times the caliber) handgun bullet is inherently no less accurate than the regular 9 or 10 degree truncated conical bullet (truncated means cut off, and the TC is a spire shape with the end cut off, usually at about 40% of the caliber). Whichever you like best and feeds best in your gun is the one to use. A common request is for dies to make a bullet with some arbitrary BC number, usually higher than anything else on the market from mass producers. But this is a little like spending all your money on a great set of magnesium wheels for your car, so you have nothing left for the engine or body work. Lots of teenagers did that when I was of that age. Today I hear the thumping of huge, overpowered speakers from expensive stereos coming from cars that could use a paint job and a tune-up, usually with the same genre of fuzzy-minded youthful driver who spent his burger-flipping paycheck for "cool mags" back in the `fifties. Putting all your attention on the ballistic coefficient and ignoring most of the other factors is very little different. The real goal is usually to hit the target at long range with greater reliability. Confusing the real goal with some narrow part of the total package that will get you there is a problem created by the myth that somehow, an arbitrary BC number bigger than anything available currently means the bullet will be more accurate. Sorry, but the BC is only a relative measure of inverse air resistance compared to some standard bullet, such as the one-inch artillery projectile that has been considered a 1.0 on the BC scale for decades. The BC means nothing by itself. You must also know the standard against which it is compared, and advertising sometimes plays on this fact to overstate the comparison or ratio by subtle use of a different standard projectile. For example, I could easily publish BC numbers of 2.50 or 3.59 or anything else I wanted, whereas most BC numbers are less than 1.0. How? By noting in the fine print, which no one reads, that the standard projectile used for comparison is a five grain wad of newspaper chewed to a soggy consistency and fired from a pursed pair of lips (yes, a spitball). More subtle yet, I could simply assume that everyone "knew" I was using a conventional 6-S 168 grain spitzer flat base bullet as my "standard", and then publish comparison BC numbers relating the bullets I was attempting to market to this standard. Not drawing any particular attention to the standard just reinforces the myth that BC has some independent value as a figure of merit. It is in fact a ratio, so it requires two items for comparison and has no meaning otherwise. Stating the BC alone is like saying the odds of the Atlanta Braves winning the next game against the Giants is "3". But three compared to what? You might assume 3 to 1. Maybe | |||
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the Giants fan meant 3 to 6, or 2 to 1 in favor of the Giants! Normally we would assume the other bullet in the implied BC figure is the old military standard one-inch projectile, but remember the old saying, "Assume makes an Ass of U and Me". Seeking a high BC is not a foolish quest, but it is foolish to think some number higher than that you read about a factory bullet will solve all your problems and improve the accuracy of your new bullet. How are you going to measure it? If you use the dual chronograph method, your measurements can be off by a very wide tolerance unless you fire a large number of rounds. Sometimes the variance is greater than the amount of supposed gain. The best way to achieve good accuracy is to judge it by the holes in the target. That is, use anything that improves the group and don't put on blinders in the quest for one specific part of the accuracy formula. High BC is desirable, but the higher spin rate it may require of the longer bullet can exaggerate normal eccentricities in the bullet, and wipe out any accuracy gains from a flatter trajectory. Each factor in the design of a bullet is part of an equation that tends to be self limiting: making any one factor too large automatically makes the others too small. You get the optimal performance by achieving the right balance of factors for your particular application, not by pushing one of them to the limit and ignoring the rest. The Myth of Critical DiameterThere can be a significant difference in accuracy between bullets of different diameter, but there is no cut and dried rule about it except that undersized bullets (compared to the rifling groove-to-groove depth of your particular gun, not to some arbitrary industry standard) generally don't shoot as well as bullets with a diameter at or slightly larger than the groove-to-groove depth. Oversized bullets tend to have minor problems in some guns with case swelling and chambering. The pressure difference is insignificant for a 0.308 inch bullet compared to a 0.309 inch bullet until you reach those loading intensities where the gun is about to come apart anyway. If it will feed and fit the chamber with the larger bullet seated in the case, it will probably shoot better than with a smaller bullet (if everything else is equal and the load is generally accurate and safe). For my money, if I were to decide on a given diameter for my swage dies, I would always choose either right on the money for diameter compared to my gun's rifling groove-to-groove depth, or slightly larger (between half and one thousandth, depending on whether it is an Auto-loader or not—some pistols have a problem with slightly larger bullets which bulge the case and cause feeding failures). On the other hand, if I had a bullet that shot well in a given gun, I couldn't care less if the bullet was undersized, lopsided and backward! The goal is to hit where you aim, and if the bullet does that, forget about what it ought to be and just be happy that it works so well. Some armchair ballisticians tend to wind themselves up so tightly in their theories that they miss the fun and the point of it all: shooting. If it works, it must be right by definition. | |||
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Many factory barrels of the same caliber are far different from each other in diameter. The differences in bore diameter at various points even in the same barrel can be far more than the wildest tolerances in any bullet. Since the whole idea of controlling bullet diameter and tolerance is to make it fit into the bore, or the rifling grooves, there's a problem here! Why worry about an overly precise bullet diameter if the bore isn't at least that precise? We've had clients send us sample bullets, pushed through a factory barrel, that came out as much as .41 caliber from a .40 caliber pistol! In one instance, the client sent the gun back twice and got two different oversized barrels, both different by as much as 0.005 inches from each other. I won't mention the gun-maker, but it is a respected name and the problem isn't unique. This doesn't mean that it isn't important to have good control over bullet diameter. It merely means that you should not take the "published specifications" for granted. Measure your gun if you really want to specify the bullet correctly to fit it. If you don't know how to measure it, you can fire a low velocity slug through it and capture the slug in water, and send us the slug to measure. By low velocity, I mean just enough pressure to get it out of the barrel reliably. Measuring a barrel is an art. Firing the bullet through it only gives you an idea of the diameter at the point where the bullet came out. Suppose your barrel has "waves" in the bore, where it varies 0.002 inches larger than the average, but the muzzle is actually tight at 0.001 smaller than the standard specifications. The bullet might expand when it passed through the big areas, but it would be drawn down again when it hit the tight spots. Which dimension is really the size of your bore? Who knows—it all depends on your meaning. Average? Mean? Tightest point? Loosest point? Standard deviation? You want a bullet to fit so it won't be distorted and so powder gas won't escape around it and cut the jacket or lead like a torch. It's worse to have gas jetting around the bullet in the loose places than it is to have the bullet slightly elongated by the tight ones (since the amount of distortion is so tiny, yet the damage by gas cutting can be so harmful to both bore and accuracy). That's why I lean toward large bullets so long as they don't cause any other problems. The fellow who says he must have a 0.2240-inch bullet for his .224 rifles could be right, if every one of them has a barrel with a .2240 maximum groove- to-groove diameter. But unless he actually knows that for a fact, he could be just as well off or perhaps better with a bullet from .2242 to .2245 diameter. The Myth of the Pressure Ring | |||