These arguments dovetailed with work being done by an engineer named Eugene Stoner, who was tinkering in his garage in Hollywood, California, during the nineteen-fifties. Shy, reserved, and opinionated, Stoner was a Marine Corps veteran who’d fought in the Pacific theatre; he lacked a formal engineering education, but had worked his way up through the machine shop at the Fairchild Engine & Airplane Corporation. By the middle of the decade, Stoner had begun to apply his experience with aircraft ordnance to firearms. Using advanced alloys and lightweight parts that were common in aeronautics, he started developing a firing mechanism for a new kind of lightweight rifle. Success was slow in coming; the barrel of Stoner’s first prototype burst in Army tests. The weight of U.S. military opinion was in favor of a heavier, more powerful weapon, the M14. His fortunes began to change when one of S.C.H.V.’s boosters, General Willard G. Wyman, asked Stoner to modify his rifle so that it could shoot a redesigned .223-calibre round weighing roughly a tenth of an ounce.
The resulting rifle, the AR-15, could fire its .223 round at more than thirty-two hundred feet per second—nearly three times the speed of sound. Stoner later explained the advantages of its smaller bullets to Congress. All bullets are “stabilized to fly through the air,” he said, but “when they hit something, they immediately go unstable.” Tiny bullets, having a smaller mass, grow unstable faster, and tumble through the body, causing disproportionate damage. As a smaller bullet tumbles, it transfers its energy to your organs and creates shock waves strong enough to sever muscle; if such a bullet strikes your head, the pressure it creates can shatter your skull or squeeze brain tissue through your sinuses. It might also fragment inside the body, scattering small pieces of itself and increasing the damage.