153 lines
11 KiB
Plaintext
153 lines
11 KiB
Plaintext
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.he CHAPTER 11 CORBIN HANDBOOK AND CATALOG NO. 7, PAGE #
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DRAW DIES
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Draw dies, or drawing dies (as they are also called), are simply
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ring dies used to reduce the diameter of a component. When you size a
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cast bullet, you are using a much less precise version of a draw die.
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The draw dies made by Corbin are extremely hard, tough venturi-shaped
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tools held in a 7/8-14 TPI body. A punch pushes the component through
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the die and out the top.
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There are two general types of draw dies. The JRD-1 can be made
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either for bullets, or for jackets. The bullet draw die reduces a
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finished bullet by a small amount, sometimes as little as 0.0005
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inches, and sometimes as much as 0.003 inches. However, greater
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reductions cause distortion of the bullet and are not feasible.
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Jacket draw dies can reduce an existing jacket by a whole caliber.
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This is the way that .41 caliber jackets are obtained today, for
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instance. A .44 caliber jacket is pushed through a draw die and
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reduced to .41 caliber. This would not work with a bullet. Jacket
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drawing punches fit inside the jacket, and actually push it through
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base first, while bullet draw dies push the bullet through nose first.
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Special versions of draw dies turn fired .22 cases into .224 or
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.243 caliber rifle jackets. The .22 WMR case can be drawn to a long
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6mm jacket in another die, and shotgun primers can be turned into free
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.25 ACP jackets with another. Draw dies perform a remarkable service.
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Their limitations are discussed in "REDISCOVER SWAGING" in detail.
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Dies ending in "R" fit the standard reloading press and have a punch
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that fits into the press ram. Dies ending in "M" fit the Mity Mite
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press, and have a punch that screws into the press ram. The die goes
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into the press head, replacing the floating punch holder. Dies ending
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in "H" are made for the Corbin Hydro-press. They have a long punch
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that screws into the ram, and the die fits into a 7/8-14 adapter which
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in turn fits the 1.5-12 thread of the press head, also replacing the
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floating punch holder.
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RFJM-22R Rimfire Jacket Maker, 22 LR to .224 caliber
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RFJM-6MR Rimfire Jacket Maker, 22 LR to .243 caliber
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SPJM-25R Shotgun Primer Jacket Maker, 25 ACP caliber
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JRD-1-R Jacket Reducing Die, specify starting and ending
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caliber.
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Draw dies for the reloading press are used by adjusting the die
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position so that you can push the component through the tightest part
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of the die using the end of the stroke. Careful die setting is
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necessary so that the component is pushed far enough into the die, yet
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the more powerful portion of the stroke is still utilized. If you
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simply put the die in the press at random settings, it might not be
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possible to push the component far enough so the next component pushes
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it out the top. Or, it might require so much effort that the operation
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becomes impossibly difficult.
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It is important to realize that effort varies quickly with the
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exact part of the stroke where the most resistance is met. This is
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adjustable by your setting of the die. Too high, and the press easily
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pushes the component in, but not nearly far enough. Too low, and the
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press has little leverage or power to do the job, even though there is
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plenty of stroke to push the component through. The optimum adjustment
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can be found in a few attempts, if you bear the critical nature of this
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balance in mind.
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It might seem as if a draw die is a very inexpensive way of
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creating a custom bullet. In a few limited instances, it is. But, for
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most calibers, reducing an existing factory bullet to a smaller size is
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more expensive than making it yourself, produces a far less accurate
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bullet, and limits you to the same weight and basic style as the
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factory bullet itself. Giving up the advantage of superior accuracy,
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the ability to make the bullet in any weight or style you wish, and the
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cost savings of using jackets and lead instead of buying ready-made
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bullets, seems like quite a bit to give up just because drawing a
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bullet down seems simple.
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The lure of getting an inexpensive bullet-production die sometimes
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overwhelms one's sense of values, though, and it isn't uncommon for
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someone to sacrifice all these advantages -- all the real power of
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bullet swaging -- in order to draw down some existing bullet. In the
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instance of the .357 and 9mm, the two 8mm diameters, and sometimes in
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the reduction of a military bullet purchased very cheaply in quantity,
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the process works well enough to justify the lost advantages. It isn't
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a general cure, and it certainly does not replace swaging your own.
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On the other hand, a jacket draw die makes good sense. The jacket
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will be expanded by internal lead pressure during swaging, so any
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diameter changes made to it are rather unimportant to the final
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product. The ability to change standard diameters, to use an existing
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longer jacket or heavier design in the next smaller caliber, is a good
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advantage. Sometimes, it is the only way to obtain a good, inexpensive
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jacket. In .41 caliber, a drawn .44 is the standard jacket used by
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bullet swagers. Likewise, for the .40 calibers.
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One does pick up a little longer draw on one side of the jacket
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when the reduction is extreme. This is unavoidable without extremely
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high cost equipment, but its effect is primarily cosmetic: the tip of
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an open tip jacket may appear uneven. Accuracy generally seems
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unaffected by this, since the jacket walls themselves seldom become
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eccentric in any normal drawing operation.
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A set of dies to make .14, .17, and .20 caliber bullet jackets
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from commercial .224 0.6-inch length jackets is available from Corbin.
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The process of making sub-calibers involves drawing the standard .224
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jacket through these three stages, stopping at the stage you desire.
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The jackets must be annealed after the first draw (from .224 to .20
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caliber) or else the end will break out on the next draw or during
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swaging.
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Since the jacket for a .17 or .14 usually is shorter than that for
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a .224, the jacket must be trimmed at some point. This can be done in
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the first draw, from .224 to .20, using a PINCH-TRIM die and punch.
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The punch is made with a shoulder, so that the shoulder to tip length
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determines the length of the jacket. Any jacket that extends beyond
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this punch step or shoulder will be sheared off as the punch passes
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through the die constriction.
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The process works well provided the correct jacket is used, since
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the temper, grain, and diameter as well as wall thickness are somewhat
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critical for proper shearing action. Usually, the jacket will be made
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quite short, and will be drawn longer in the .17 and .14 stages. The
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exact final length is a bit experimental, since variations in jacket
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lots, temper, wall thickness, and material composition will produce a
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somewhat different final drawn length. But it seems quite consistent
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within one lot or kind of jacket.
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Jacket and bullet draw dies that fit the reloading press or the
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Mity Mite press require careful adjustment so that the maximum leverage
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can be properly utilized to push the component through the tightest
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point in the die, yet still gain maximum stroke within the required
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leverage range. In some cases, such as drawing copper tubing to make
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long rifle jackets, there isn't any easy way to get enough stroke and
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enough power at the same time. In those instances, a short "helper"
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punch or rod must be used.
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The jacket is drawn in two stages. First, the jacket is started
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into the die using the end of the stroke, where there is sufficient
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power. Then, the ram is drawn back, the helper rod inserted in the
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jacket, and the ram is run forward again, gaining extra stroke to push
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the component all the way through the ring die. This is, admittedly, a
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slower way to do the job. But in some cases, it is the only thing that
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works in a hand press.
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Dies made for the Hydro-press, on the other hand, seldom have any
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such difficulties because the programmable Hydro-press develops
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whatever power is needed, at any point in the stroke cycle. With a
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full six inches of stroke to work with, and full power from top to
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bottom, it is a simple job to draw just about any length or thickness
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of jacket in one stroke. Copper tubing jackets are a product that
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point up the advantages of the Hydro-press design.
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Remember that in most home swaging operations, you are
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accomplishing tasks in very few steps, with relatively inexpensive
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equipment, that the major factories spend tens or hundreds of thousands
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of dollars in time and equipment to accomplish, often in 10, 12, or 14
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stages. Sometimes, there are obvious limitations to what you can do
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without a bit of leeway in your final lengths or weights. (Sometimes,
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the amazing thing is that the process works at all!)
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On the other hand, for the person who doesn't mind experimenting
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and can put up with things coming out just a bit differently than his
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original blueprints might have demanded, these processes offer a great
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deal of freedom from high costs, abritrary supply sources, and the
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ability to make bullets that are extremely accurate and unusually high
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in performance. Just don't confuse accuracy and performance with
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predictable adherence to a pre-existing design concept! Sometimes, the
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way it happens to come out is what you have to work with, in the
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practical world of limited costs, simple operations, and available
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supplies. Fortunately, the way it comes out is usually pretty darn
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good!
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