ACP
Automatic Colt Pistol
ACP is an abbreviation used to describe the real-steel .45 calibre semi-automatic pistol bullet. Invented by Colt for their 1911 range, this bullet is larger and more powerful than many, but the increased size does not allow many rounds to be stored in the gun prior to shooting. Airsoft Colt 45 replicas are often called 'Airsoft Colt 45ACP replicas', although they actually still use the same 6mm plastic BB that is used throughout airsoft.