Sentence:  The US Army adopted John Browning's M1911 pistol as its sidearm, chambered in .45 ACP (<WSD>Automatic</WSD> Colt Pistol). 
Meaning of the word marked with <WSD> tags:  An autoloader; a semi-automatic or self-loading pistol, as opposed to a revolver or other manually actuated handgun, which fires one shot per pull of the trigger; distinct from machine guns.