NAME – 5.7×15.6R M24

NAME (COMMON) – M24 .22 Long Rifle

TYPE – Rimfire

YEAR OF INTRODUCTION – 1944

COUNTRY OF ORIGIN – USA

CASE TYPE – Rimmed straight

CARTRIDGE LENGTH – 25.3 mm (0.995 in)

CASING LENGTH – 15.6 mm (0.613 in)

CASE HEAD DIAMETER – 5.7 mm (0.225 in)

CASE RIM DIAMETER – 7 mm (0.275 in)

BULLET TYPE – Round nosed full jacketed ball

BULLET DIAMETER – 5.7 mm (0.223 in)

BULLET WEIGHT – 2.62 g (40.5 grains)

POWDER WEIGHT – 0.16 g (2.5 grains)

CASING WEIGHT – 1.64 g (9.8 grains)

TOTAL ROUND WEIGHT – 29 g (52 grains)

MUZZLE VELOCITY – 343 m/s (1125 fps)

NOMINAL BARREL LENGTH – 35.6 cm (14 in)

MUZZLE ENERGY – 154 j (114 ft/lb)

     This was an unusual load for the .22 Long Rifle developed during the last years of World War II. The round was initially intended for use in survival rifles issued to aircrewmen. The idea was that the normal .22 long rifle lead bullet load would run against the Hague Convention Accords against the use of deforming bullets in combat. The fully-jacketed M24 (originally T42) round would prevent any arguments that a lead bullet was being used by servicemen. In 1945, the OSS also asked that this round of ammunition be loaded for their use in the suppressed High Standard .22 pistol.