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