The raw material for making a bullet usually consists of a lead core, and a jacket, or sometimes just the lead core itself. While lead can be cut from spools of wire, using the Corbin PCS-1 Precision Core Cutter, or the larger PCS-2 Magnum Core Cutter, for those who have a good supply of cheap lead, it may be more desirable to cast the cores.

Casting cores is practical from .185 to .365 diameter (suitable for .224 through .458 jacketed bullets, or .20 to .375 lead bullets, with the CM-4 Adjustable Core Mould, which makes four lead cores of adjustable weight at one time. Larger diameters, from .365 up to .700 inches, can be made three at a time with the CM-3 Magnum Core Mould (since the physical size of a four-cavity mould becomes so great that too much heat is radiated from the surface area, making it difficult to keep a large cavity, four-cylinder mould at proper operating temperature).

The CM-4 mounts to the reloading bench (or, for those who mount a vise on their bench, to a short piece of 2 X 4 inch wood which is then clamped in the vise). There is no need for a mould handle, as the sprue cutter is long enough to push gently with a gloved hand (wear heat-resistant gloves and face protection when handling molten lead). The lead is simply poured into the "bathtub" slot, in the top of the sprue cutter/handle. It runs down into the cylinders, which are fitted with pistons that rest on an adjustable stop bar. The bar can be set to different heights, to change the volume displacement of the cylinders, and thus make different weights of cores.

The sprue cutter/handle is moved to one side, cutting the sprues flush with the top of the cylinders. Then the stop bar is pushed up, which raises all the pistons at once, and pushes the lead cores out the top of the mould. A box placed under the mould to catch the cores when they are pushed over, upon closing the sprue cutter/handle, completes the picture. Using an ordinary open top lead melting pot and a good-sized ladle is the best way to pour the lead. Bottom pour pots designed for bullet moulds can be used, but a ladle should be filled and then used to transfer the hot lead to the core mould. The sprue left in the top can be lifted out with a pair of needle nosed pliers, or a bend paper clip with the end projecting into the sprue area so that the sprue solidifies around it.

The CM-4 is available in .185, .204, .218, .247, .275, .312, .340, and .365 diameter. For details and help with the correct diameter for any bullet, contact Corbin.

• Use clean lead.
  Reclaimed range lead and wheel weights usually are infiltrated with road dust, dirt, rock dust, and hard silica dust. Most of these impurities float on molten lead, and can be carefully skimmed from the top of well-fluxed lead as a dross. Impurities in the core will scratch the inside of the steel cylinders, making gouges into which the lead will "lock" when it cools. This makes the pistons hard to move, or even freezes them in place. Clean lead removes this source of trouble.
  
  
• Do not beat on the ejector bar or pistons
  Striking the ejector bar (rest plate) or the pistons in an attempt to make a "stuck" lead core eject will usually ruin the piston rod or cause other damage. Never beat upon any part of the mould. If a piston sticks in a cylinder, stop! Turn the mould upside down, remove the rest plate, put a heat-safe hot lead catching box or tray under the mould, and gently heat the stuck cylinder with a propane/air torch (not an oxy-assist or acetylene torch!) until you can remove the piston. Lead smears can be removed from the cylinder with a wrap of extra-fine 0000 grade steel wool wrapped on a cleaning rod. Stroke the rod in a straight back and forth motion in the heated cylinder (basically, melt out the lead and then wipe the smeared lead away). Do not chuck the cleaning rod in a drill motor and spin it in the cylinder. This will put circular grooves in the ID of the cylinder, which will further lock the next core into it. Straight lines are not a problem. The core will slide out even if there are vertical lines in the cylinder. Please note that if you pound on the mould to try and get something to move, you will probably ruin it, and this abuse will not be covered under warranty.
  
  
• Use enough heat.
  When casting in the four cavity steel mould, there is a considerable amount of heat radiation away from the surface area of the mould. It is necessary to use a higher lead temperature than you would with a standard bullet mould, or else the lead will cool off too quickly and result in partially filled cylinders.
  
  
• Use a large enough ladle.
  Small ladles tend to lose heat quickly, so that the lead cool and block the holes in the mould before it can pour to the bottom. Use a large enough ladle so that there is plenty of reserve heat to keep the lead molten as it pours.
  
  
• Avoid high tin ratios.
  The steel mould cylinders will tend to "solder" to a high tin content alloy. Using antimony to harden the lead instead of tin will help prevent this. Casting solder alloys is not recommended.
  
  
• Avoid bismuth alloys.
  Bismuth alloys usually expand on cooling, just the opposite of most metals. If the core expands in the cylinder as it cools, it will try to lock itself into the cylinder. The only safe way to remove it will be to turn the mould over, remove the piston, and carefully melt the metal out of the cylinder by application of a propane torch to the cylinder. Linotype is an alloy containing bismuth, and tends to expand on cooling. It is also too hard for most swaging operations.
  
  
• Make sure the pistons are down before closing the sprue plate.
  If the pistons do not fall back down, check for tin/lead soldering in the cylinders, scratching from abrasive contaminants in the lead, or other reasons why the piston might be hard to move. If the pistons project from the top of the mould and you close the sprue plate, it will damage the piston, which may be bent or enlarged so it cannot drop back through the cylinder. If this happens, removal of the piston may require machine work to avoid damaging the cylinder.
  
  

Corbin Manufacturing & Supply, Inc.
PO Box 2659
White City, OR 97503 USA

Phone 9am-5pm Mon-Thurs: 541-826-5211
Fax 24-hrs: 541-826-8669
Website: http://www.swage.com
E-mail: sales@corbins.com