How the Colt M1911 Was Adopted by the U.S. Army iStock-472611184 On March 29th, 1911, the US Army Ordnance Department accepted the Colt M1911 into service. This semi-automatic pistol would remain in service for over seventy-five years and would go on to influence generations of handguns to come. Today, the 1911 platform has grown from its roots and remains one of the most popular and identifiable pistols in the world over a century after its ado…