During World War II, American G.I.s called the German MG42 machine gun “Hitler’s buzz saw” because of the way it cut down troops in swaths. The Soviet Red Army called it “the linoleum ripper” because of the unique tearing sound it made—a result of its extremely high rate of fire. The Germans called the MG42 Hitlersäge or “Hitler’s bone saw”—and built infantry tactics around squads of men armed with the weapon. Many military historians argue that the Maschinengewehr 42 was the best general-purpose machine gun ever. It fired up to 1,800 rounds per minute in some versions. That’s nearly twice...