The ammunition the Germans developed for what would become the first mass-produced assault rifle, the Sturmgewehr (StG) 44, was the same caliber as the standard German rifle ammunition (7.98 mm) but with a case that was considerably shorter: 33 mm versus 57 mm. This meant that while the bullet was the same size, it was propelled by a smaller amount of gunpowder. The gun kicked less and was easier to control, even when set to automatic, and fired at a rate of 600 bullets per minute. The 98K it was intended to replace was not even semi-automatic. The StG 44 was not lighter than the 98k, but it had a barrel that, at 16.5 inches, was about half a foot shorter. It also had a 30-round magazine, compared to the 98K’s five-round magazine. Of course, the StG 44 packed less punch than the 98K and was not as accurate at extreme distances, but the Germans understood that the StG 44 was deadly enough. Fortunately for the Allies, the Germans did not issue many StG 44s until late in 1944, at which point having a better gun wasn’t enough to turn the tide of the war.

Other countries quickly developed similar weapons. The Soviets, impressed with the StG 44, developed their own version of the gun, called the AK-47. The British took a different approach with the EM-2, which had an even smaller cartridge (.280 caliber, or 7 x 33 mm). The U.S. was more conservative, to the point that the nation forced the British to abandon the EM-2 because the U.S. wanted NATO to accept as its standard ammunition a slightly modified version of the venerable 7.62 x 63mm “thirty-ought-six” used in the M-1, a new round that measured 7.62 x 51 mm.

Still, the Army wanted something better than the old M-1 rifle, which opened the door in the 1950s to new ideas. Two organizations within the military conducted research that helped undermine Army orthodoxy: the Operations Research Office (ORO) and the Ballistics Research Laboratory (BRL). ORO studied the Korean War and came to the same conclusion the Germans had during World War I: Soldiers mostly shot at targets much closer than what they were trained to shoot at and what their guns were capable of hitting. Few even saw targets or aimed; instead, they conducted “area fire,” which means they fired as quickly as possible at an area to suppress the enemy. ORO also determined that in combat the best marksmen fired no better than the worst, and firing quickly was more important than firing accurately, within reason. The BRL analyzed ballistics tests and concluded that the lethality of a bullet had more to do with its speed than with its mass. If a small .22 (5.56 mm) caliber bullet went fast enough, it was as deadly as the NATO 7.62 x 51 mm round—and more accurate. Nonetheless, the Army favored a big orthodox rifle, the M-14, which fired the NATO 7.62 round and had a 20-round magazine. It could fire on automatic, but because of the ammunition it was difficult to control on that setting, and most kept it set at semi-automatic to avoid wasting ammunition.