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