M16 PUBG Low-poly 3D model

In 1928, a U.S. Army 'Caliber Board' conducted firing tests at Aberdeen Proving Ground and recommended transitioning to smaller caliber rounds, mentioning, in particular .27 in (6.86 mm) caliber. Largely in deference to tradition, this recommendation was ignored and the Army referred to the .30 in (7.62 mm) caliber as full-sized for the next 35 years.[27] After World War II, the United States military started looking for a single automatic rifle to replace the M1 Garand, M1/M2 carbines, M1918 Browning automatic rifle, M3 Grease Gun and Thompson submachine gun.[28] However, early experiments with select-fire versions of the M1 Garand proved disappointing.[29] During the Korean War, the select-fire M2 carbine largely replaced the submachine gun in US service[30] and became the most widely used carbine variant.[31] However, combat experience suggested that the .30 carbine round was underpowered.[32] American weapons designers concluded that an intermediate round was necessary, and recommended a small-caliber, high-velocity cartridge.[33]