This is Colt .45 M1911A1 except it doesn't look like one (all the proportions are drawn wrongly).
It was a standard-issue side arm in the US force for a long time, from 1911 (hence M1911=Model of 1911) until it was replaced by Beretta 92 in 1985. It was used in WW1, WW2, Korean and Vietnam wars.
Cartridge: 45 ACP. Action: Short Recoil Operation. Range: 75yrd (62m). 7 rounds max. Weight:1130g. Designed by John Browning.