Editing M1 Abrams (section)

====M68A1 rifled gun====
[[File:XM1 Abrams interior.jpg|thumb|right|XM1 interior]]
[[File:U.S Army M1 Abrams 105 mm rounds laid out Desert Shield.jpg|thumb|right|105&nbsp;mm [[APFSDS]] rounds are laid out in Operation Desert Shield, 1991]]

The main armament of the original model M1 and IPM1 was the M68A1 105&nbsp;mm rifled tank gun firing a variety of [[Armour-piercing fin-stabilized discarding sabot|APFSDS]], [[High-explosive anti-tank|HEAT]], high explosive, [[white phosphorus]] rounds and an [[anti-personnel]] (multiple [[flechette]]) round. This gun used a license-made tube of the British [[Royal Ordnance L7]] gun together with the vertical sliding breech block and other parts of the U.S. T254E2 prototype gun. However, a longer ranged weapon was always envisaged, with lethality beyond {{convert|3|km|adj=on|sp=us|order=flip}} to combat newer armor technologies. To attain that lethality, the projectile diameter needed to be increased. The tank was able to carry 55 105&nbsp;mm rounds, with 44 stored in the turret blowout compartment and the rest in hull stowage.

Being non-combustible, the empty cartridge cases of the M1 variant accumulated on the turret floor after firing. After allowing some time to cool, they were ejected out of the hatch by the loader.{{sfn|Green|Stewart|2005|p=62-65}}