Colt AR-15
The Colt AR-15 is a lightweight, magazine-fed, gas-operated semi-automatic rifle. It is a semi-automatic version of the M16 rifle sold for the civilian and law enforcement markets in the United States. The AR in AR-15 stands for ArmaLite rifle,... Wikipedia
Action: Direct impingement
Barrel length: 20 inches (510 mm) (standard); 16 inches (410 mm) (carbine); 24 inches (610 mm) (target)
Cartridge: .223 Remington; 5.56×45mm NATO
Feed system: Issued with 5-, 10-, 20- & 30-round STANAG magazines
Manufacturer: Colt