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Corbin Handbook and Catalog No. 7 Chapter 02
.he CHAPTER 2 CORBIN HANDBOOK AND CATALOG NO. 7, PAGE #
MAKING THE LEAD CORES
The two main components that go into most bullets are the lead
filling, or core, and the outer skin, or jacket. We'll talk about
jackets in the next chapter. Right now, let's make some cores.
There are two main sources for lead cores. You can purchase a
spool of lead wire in the proper diameter, along with a core cutter,
and chop off accurately-measured lengths. Corbin has lead wire in pure
175,000 grain spools (LW-25), and the PCS-1 Precision Core Cutter to
cut them. The core cutter has an adjustable stop screw that adjusts
the amount of lead cut on each stroke of the tool.
The second source is your own supply of scrap lead, the same as
you might use for bullet casting. Corbin makes a 4-cavity, adjustable
weight core mould that mounts to the reloading bench. You don't have
to pick it up, and there are no handles required. Four pistons,
precision fitted to four cylinders, slide up and down to eject the
cores. The bottom position is set by a rest plate. This steel plate
rests on a pair of nuts, fastened to two threaded rods at either end of
the mould.
Adjusting the nuts upward decreases the volume in the cylinders,
and gives you a lighter core. Pouring molten lead into the top of the
mould fills all four cavities. Moving a long sprue cutter chops off
the lead at the top of the cavities, leaving even lengths of lead to be
ejected straight up from the cylinders. The process is very fast,
making it possible to produce at least 1000 cores per hour.
Lead wire can also be manufactured at home. Corbin makes a lead
wire extruder kit for the Hydro-press, capable of making lengths of
lead wire from lead billets. Lead wire can be extruded in special
shapes, as well, for use in stained glass work or as hollow tubing used
for fishing sinker wire. The LED-1 Lead Extruder Die set comes with a
selection of popular diameters of interchangeable dies, all of which
fit into a master body. Included with the kit are billet mould tubes
to form the proper diameter of lead cylinders for extrusion. These
special forms can be the basis of additional income for the Hydro-press
owner. Hand presses do not have sufficient stroke or power for
commercial lead wire extrusion.
Small diameter lead wire for the sub-calibers (.14, .17, and .20)
can be produced in the Corbin hand presses with the LED-2 extruder kit.
Only relatively short lengths are made at one time, but they are very
economical sources of cores for the tiny sub-caliber bullets.
For those who wish to make commercial quantities of lead wire,
Corbin manufactures the EX-10 lead wire extruder, a dedicated, single-
purpose machine to produce any size or shape of lead wire in 10 pound
spools. The EX-10 uses lead billets of 2-inch diameter, which can be
cast using Corbin's tube moulds. Write for specific information on
this product.
Lead wire for bullet cores can be used in two ways, and the
diameter depends on what way you plan to use it. You can simply swage
the lead into a finished bullet, with no jacket. In that case, the
lead only has to slip easily into the smallest die bore in the set you
are using. Dies made only for lead bullets are at final diameter of
the bullet, and consequently your lead core should be just a little
under bullet diameter.
If the lead is too small in diameter, it will stick out the die
mouth before you have enough of it to make the weight you desire. That
is a situation to avoid -- never apply any pressure to a component that
isn't completely contained within the die. The punch will probably
slip off to one side and be damaged by striking the mouth of the die.
The exact diameter isn't important as long as the core fits into the
die easily and doesn't stick out the die mouth.
But if you want to make a jacketed bullet, then the core has to
fit inside the jacket (obviously!). You cannot start with a .357
caliber lead bullet and somehow "put a jacket on it" to wind up with a
.357 caliber jacketed bullet. Instead, you use lead wire or a cast
core that fits inside the .38 jacket, and expand it upward in the die.
The lead pressure expands the jacket right along with it, resulting in
a tight, uniform assembly.
The walls of a .357 or .38 caliber jacket are usually about .017
inches thick. There is a wall on both sides of the core, and the
jacket normally is made small enough so that it will work for .355
(9mm) as well as .38 caliber. Bullet jackets are almost always
considerably smaller than the final bullet diameter so that they can be
expanded upward from core seating pressure.
This means that you have a jacket with an outside diameter of
about 0.354 inches, minus two walls of 0.017 inches, for a remaining
inside diameter of about 0.320 inches. Better quality jackets have
tapered walls, so that the base is even thicker. In practice, a 0.318
inch core will fit inside most .38/.357 caliber jackets properly.
But for higher precision, a die set for the Corbin presses usually
includes a separate core swage die, which accepts the raw lead core and
reshapes it to a more perfect cylinder, flattens the ends nicely, and
expands the core diameter very slightly in the process. The die also
extrudes a small amount of lead from the core to adjust the weight.
Because of this extra die, it is necessary to use a bit smaller
diameter of core. A 0.312 inch lead core fits nicely into the standard
0.315 to 0.318 inch core swage die, allowing for any bending or denting
that the core might receive in handling. And that is how we arrive at
the proper diameter of lead wire to use for any set of dies, in any
caliber. For jacketed bullets, the core must fit into the jacket and
it must also fit easily into any core swage die that is part of the
set. For lead bullets, the core must at least fit into the final die
and not be so long that it sticks out the die mouth.
In the CM-4 Core Mould, six diameters cover most of the bullets
you might wish to make. The .224 mould makes a core of about 0.185
inch diameter, which works well in the 6mm and .25 as well as the 6.5mm
caliber. The .257 caliber mould crosses over slightly into the .25 and
6.5mm caliber range, but since different jackets have different wall
thickness, it is useful for thinner wall .25 jackets and thicker wall
.270 and 7mm jackets.
The standard 7mm jacket takes a 0.218 inch core, so a 7mm core
mould is made in that size. The .30 calibers all take a 0.250 inch
core, as do most of the .32 and .338 jackets. Heavy walled tubing
jackets in large bores can use the same core size as a standard jacket
might in a smaller caliber. A pair of standard sizes cover the .38 and
the .44-45 calibers. These are 0.312 inch and 0.365 inch,
respectively. A slightly smaller size is made for the .41 caliber and
the .40 Bren 10 caliber.
Using the next smaller size normally serves quite well, without
the expense of having a custom mould built. However, custom moulds CAN
be made to order if desired. For large diameters of lead, Corbin
builds special moulds to order at a correspondingly higher cost than
the CM-4. Moulds for billets of half inch diameter can be used for
shotgun slugs. Tube moulds, which have a steel base with a plug that
slips into the bottom of a honed steel tube, are generally used for
large diameter billets.
Lead cores are discussed in great detail in the book, "REDISCOVER
SWAGING". The advantage of using a lead core mould is the lower cost
of using scrap lead. The advantage of using lead wire is the neatness,
safety, speed, and ease of use. There is not much difference in
potential accuracy. Lead wire has a slight edge over cast cores
because of the great uniformity of the extruded product.
You probably wonder about the hardness of the lead: can you use
wheelweights, or casting alloys to swaging bullets? The answer depends
on the caliber, and the system of swaging you plan to use. In most
reloading press dies, you can't quite generate enough pressure to swage
any lead harder than about Brinnell Hardness 8 (or about 3 percent
antimony/lead alloy) before breaking either the die or the punch. But
in certain circumstances, you can even swage linotype alloys of
Brinnell Hardness 22. The Corbin Hydro-press can swage any alloy of
lead ever made, or even solid copper if you wish.
The reason that you can swage hard alloys in some calibers and not
in others, in some shapes and not others, and in the Hydro-press but
not in a reloading press has less to do with the power of the press
than it does the strength of the dies and punches. If you are curious
about the mathematics involved in engineering dies to withstand certain
pressures, the book "POWER SWAGING" is full of revealing data,
formulae, and charts that will make it all clear.
As a rule of thumb, it's safer to use soft, pure lead for swaging
in all circumstances because pure lead flows more easily at lower
pressures, and thus puts less strain on the dies. But, if you have a
need to swage hard lead for some reason, don't give up just because of
a rule of thumb! We have a way to do it in every case, if you are
willing to purchase the correct kind of tooling. Your stock of casting
alloys can be used if the caliber, die, and press system is selected
with proper specifications for hard lead. Tooling made for hard lead
may, in some circumstances, not be as useful for soft lead because of
the different size bleed holes. That is one reason why you need to
talk to the die-maker before jumping in head first with a bar of hard
alloy in hand!
If you use Hydro-press dies, hard lead is perfectly acceptable
in calibers up to .500 diameter, unless very deep and thin base skirts
or other special designs are planned. The dies are so strong that they
can handle any lead alloy. In the Mity Mite system, hard alloys can be
handled if the die-maker knows in advance you plan to use them. In
calibers above .358 diameter, they are a bit risky because of the die
wall in the smaller Mity Mite series -- an imprudent stroke of the
handle could crack a .45 caliber die used with too hard an alloy. In
the reloading press, calibers of .243 and .224 work reasonably well
with hard lead, but anything larger should be used with alloys of
Brinnell Hardness 6 and under. Corbin supplies pure lead in billets
and in lead wire form, but does not furnish alloy lead except on
special order.
A potential objection to lead wire is the cost of shipping. At
the time of this writing, it costs about $10 to ship a spool of lead
wire completely across the country. A spool of .22 caliber wire makes
over 4,000 .224 bullets. The cost of shipping, then, breaks down to a
mere 0.0025 cents per bullet (that is a quarter of a penny per bullet).
This amount is not prohibitive, and consequently most people choose to
use lead wire for the smaller calibers. In the larger calibers, the
cost per bullet increases since there is more lead consumed in each
bullet, but the trade-off of convenience and safety still results in a
majority of bullet-makers using lead wire.
Corbin has lead billets in 0.795-inch diameter for use in the LED-
1 extruder die (in case you don't care to cast billets), and can
furnish lead in just about any size of billet. Alloys can be furnished
only in minimum lots that generally are 100 to 250 pound, because of
the minimum billet required for a commercial extruder operation. Many
of our customers can provide you with the smaller quantities of alloy
leads: check the "WORLD DIRECTORY of CUSTOM BULLET MAKERS" for
addresses and phone numbers.
