A barrel design in which fired bullets having a spool-like body are squeezed to a smaller diameter in passing from the breech to the muzzle. The idea of this firearm was to present a large cross-sectional area of the projectile to the propellant gases and to present a small cross-sectional area to the atmosphere in order to reduce air resistance and thus increase the muzzle velocity of the projectile. Also known as a Gerlich type gun, a taper bore gun, or a reducing bore gun.
1