I find these to be very useful to diagnose malfunctions in all types of firearms, especially semiautomatic pistols. If one first removes the recoil spring, the slide can be manipulated very precisely so you can watch what is going on in slow motion.
Most gunsmiths I know make them as follows. It should not require mention (but I'll mention it anyway) that it should be an ironclad, strictly observed rule that NO live ammo is ever permitted on a bench where guns are being worked on.
First, do not use fired cases. They are swollen oversized and are unsatisfactory. Make dummies from live, unfired rounds, of a good standard U.S.-made ammo of reliable dimensional conformity, if available in that caliber. Read that Remington, Winchester, Federal or military. For normal testing use FMJ, unless you intend to test functioning with some other specific type of bullet.
Pull the bullet with an inertia puller, dump the powder, chamber the case in a gun and fire it. DO NOT RELY on killing primers with WD40 and the like. They are harder to kill than a vampire, and I have seen them fire after a 24-hour saturation. (A primer alone will develop enough energy to drive a bullet several inches down a pistol barrel, and just possibly clear the muzzle. It can hurt you or at least give you a brief case of uncontrolled excretion. ) So: after you have killed the primer BY FIRING IT, carefully re-seat the bullet in the cartridge case to its original depth, secured with a drop of epoxy or crazy glue. Make sure the bullet went in straight, without burring the case mouth or bulging the case wall. (If it did not, it will not make a good dummy; throw it away and start over.)
Finally, hold the cartridge in a V-block and drill a 1/8" or 3/16" hole through the side of the case; drill carefully and gently so as not to distort the case with drill pressure (the previously seated bullet will help). Deburr the hole. The hole instantly distinguishes the dummy from live ammo or a dud.
There. You now have one dummy. For a semi-auto pistol, two should be enough to replicate most malfunctions, one feeding and one in the mag directly below.
M
Most gunsmiths I know make them as follows. It should not require mention (but I'll mention it anyway) that it should be an ironclad, strictly observed rule that NO live ammo is ever permitted on a bench where guns are being worked on.
First, do not use fired cases. They are swollen oversized and are unsatisfactory. Make dummies from live, unfired rounds, of a good standard U.S.-made ammo of reliable dimensional conformity, if available in that caliber. Read that Remington, Winchester, Federal or military. For normal testing use FMJ, unless you intend to test functioning with some other specific type of bullet.
Pull the bullet with an inertia puller, dump the powder, chamber the case in a gun and fire it. DO NOT RELY on killing primers with WD40 and the like. They are harder to kill than a vampire, and I have seen them fire after a 24-hour saturation. (A primer alone will develop enough energy to drive a bullet several inches down a pistol barrel, and just possibly clear the muzzle. It can hurt you or at least give you a brief case of uncontrolled excretion. ) So: after you have killed the primer BY FIRING IT, carefully re-seat the bullet in the cartridge case to its original depth, secured with a drop of epoxy or crazy glue. Make sure the bullet went in straight, without burring the case mouth or bulging the case wall. (If it did not, it will not make a good dummy; throw it away and start over.)
Finally, hold the cartridge in a V-block and drill a 1/8" or 3/16" hole through the side of the case; drill carefully and gently so as not to distort the case with drill pressure (the previously seated bullet will help). Deburr the hole. The hole instantly distinguishes the dummy from live ammo or a dud.
There. You now have one dummy. For a semi-auto pistol, two should be enough to replicate most malfunctions, one feeding and one in the mag directly below.
M