Multi-part stacking bullets can be loaded into straight cases like the .357 Magnum and .45 Long Colt. Bullets that are composed of two or three independent sub-bullets, stacked together with a nose that fits into a hollow base on the next bullet ahead of it, can be loaded as a single projectile, and will separate slightly in flight. The drag on the base of the rearmost bullet will retard it, allowing the next bullet segment to retard and separate in turn. The result is a string of bullets, similar to a shot string from a shotgun shell, which impact in a tight pattern at 50 to 100 feet.
The benefits of multi-part bullets are that they lower the net penetration depth, while delivering the same total energy to the target. With three separate strikes, the bullets have a better chance of hitting a vital area in defense situations. With less penetration of each separate part, the risk of passing through the target and causing collateral damage is reduced. In night shooting situations, the ability to fire small groups with each pull of the trigger gives a nervous, frightened home defender greater odds of disabling an intruder quickly.
The bullets can be made with half-jackets (exposed lead noses) or entirely of lead. Or the rearmost bullet can be a Base Guard, gas check or half jacket. An easy way to make the bullets is to use the JSWC-2 two-die set. This set consists of a core swage die, to make accurate weight cores, and a core seating die, to form the base and nose and optionally seat the core into a jacket. The normal JSWC-2 die set has a base punch (internal) and a nose punch (external) for the core seat die. The addition of two other punches, a hollow base internal punch and a matching nose punch. The special "stacking punches" added to the set allow production of matching truncated conical nose and base.
The base section is made by using the standard base (for example, a flat base) internal punch with a stacking "nose" or projection-forming punch. The middle section (of three-part bullets) is made by using the same stacking nose external punch but changing to a hollow cavity stacking internal punch. The nose section is formed by changing the external nose punch to a standard shape, but keeping the same hollow base punch in place.
After forming the individual sub-bullet sections (each weighing either half or a third of the weight of the total projectile assembly, which in turn is a normal safe weight for the caliber), clean them of all lubricant with a good solvent such as Corbin cleaning solvent. Then stack them together, insert the assembly into the core seat die with the normal base and nose punches installed, and lightly swage the bullet together for a perfectly fitted stack.
The bullet can be loaded into straight cases, but should not be used in bottleneck or tapered cases where there is any chance of the rearmost bullet section dropping free into the powder area. As long as all three (or two) segments are firmly seated into a case neck, or a straight case, the total weight of the separate segments can be used as if it were one projectile, and normal loads for that weight can be used.
The "socket and tang" design (hollow base that matches the angle and depth of a truncated conical nose) can be used with half-jacket style bullets. The front section can also be formed in a normal point forming die, using a socket-type hollow base punch, if the SWC shoulder isn't desired. Since the purpose of these bullets is primarily close range defense, the shoulder is usually a good feature, adding impact shock. In autoloaders, the front section can even be a full metal jacket formed by reversing a normal 3/4-length jacket and seating a lead core into it with the hollow base stacking punch. Since the point forming die is slightly larger than the core seater, this would require a different base punch. Also, the point form die uses an external base punch, and the core seater normally uses an internal base punch.
