Share This: The 1911, or M1911, or the M1911A1 likely places first in a competition of the world’s most popular pistol. It served the United States from 1911 to 1985. Along the way, it fought in two world wars, a conflict in Korea, that communist hunt in Vietnam, and still chugged along with spec ops into the war on terror. So what do you know about the M1911? Well, after this article, you’ll know it all. The Basics of the M1911 The M1911 is a semi-automatic, single-action-only pistol that operates off of a short recoil system. It utilizes the 45 ACP round and feeds from a single stack magazine. Over time the pistol’s popularity has seen it become chambered in dozens of different calibers, from 22LR to 50 G.I.