DESIGN AND FABRICATE A HIGH-VELOCITY CALIBER .22 CARTRIDGE, MODIFY A STANDARD M2 CARBINE TO FIRE THE CARTRIDGE, AND EVALUATE THE WEAPON-AMMUNITION COMBINATION. 25th Report on Project TS1-2

A high-velocity, small-caliber cartridge was designed to improve the effectiveness of the M2 carbine. The 0.22-cal cartridge had a 41-grain bullet, an 18.0-grain charge, a 145-grain total wt, a 1.700-in. length, and a 0.375-in. diameter. Ballistic data were obtained by lumiline initiators at 28.5 and 78.5 ft and 2 make-circuit screens at 580 and 620 ft from the muzzle. A charge of 2 grains of IMR 4227 and 16 grains of IMR 4198 gave a muzzle velocity of 3022 fps and an instantaneous velocity of 2866 fps at 78 ft. Four ten-shot targets at 100 and 300 yd showed mean radii of 0.38 and 2.01 in., mean vertical deviations of 0.28 and 1.20 in., mean horizontal deviations of 0.22 and 1.41 in., extreme vertical deviations of 1.15 and 4.40 in., extreme horizontal deviations of 0.75 and 5.38 in., and extreme spreads of 1.20 and 5.97 in., respectively. At 50 yd, 5 lead-core ball slugs perforated a 0.25-in.-thick, mild steel plate. Perforations were obtained in 0.5-in.-thick mild-steel plate with AP slugs. Five AP rounds fired against 0.25-in.-thick homogeneous plate gave 4 perforations and 1 penetration. Against face-hardened plate of the same thickness, 4 perforations and a 0.07-in. penetration were noted. An M1 helmet and an M12 armored vest were perforated at 350 and 250 yd, respectively. The tests indicated that the 0.22- cal weapon is superior to the 0.30-cal M2 carbine in trajectory, velocity, penetration, and accuracy in semi-and full-automatic fire, and compared favorably with the M1 rifle at ranges up to 300 yd.