6mm Squeezebore

An armor-piercing round designed to increase the penetrating power of the M4 Carbine at all ranges.

While tungsten-cored rounds like the M995 are definitely effective versus modern heavy body armor, they are very expensive: M995 five costs over five times as much as M855.

Requiring only a barrel change, the 6mm Squeezebore round would fire a 1.5g steel-cored bullet at 1,500 m/s. The tapering bore generates higher pressures past the highest pressure part of the curve, increasing the efficiency of the cartridge from barrels over 8" long. At 500m, it retains 460J, more energy than M855, M193, or M995. By the time the bullet exits the muzzle, the annular flange on the side of the bullet is would be squeezed down to 4.5mm diameter.