The ArmaLite AR-15 is a selective-fire, 5.56×45mm, air-cooled, direct impingement gas-operated, magazine-fed rifle, with a rotating bolt and straight-line recoil design. It was designed above all else to be a lightweight assault rifle, and to fire a new lightweight, high velocity small caliber cartridge to allow the soldier to carry more ammunition. It was based on the Armalite AR-10 rifle. After modifications (most notably, the charging handle was re-located from under the carrying handle like AR-10 to the rear of the receiver), the new redesigned rifle was subsequently adopted as the M16 Rifle and went into production in March 1964. The Armalite AR-15 is the parent of a variety of AR-15 variants.