An assault rifle is a select-fire rifle chambered in an intermediate rifle caliber (5.45 Russian, 5.56/.223 Rem, 6.8 SPC, 7.62 Soviet, or other similar calibers). Fire mode is controlled by a selector switch or lever. Its primary role is that of a weapon that delivers more precision firepower than a submachine gun at moderate range without the bulk of a full-power battle rifle or the recoil. The lesser weight of the rifle and rounds allow soldiers and marines to carry more ammunition in field ops.
Assault rifles usually serve as military service rifles, as well as police patrol rifles and as civilian defensive rifles (usually configured to fire in semi-automatic only). The assault rifle allows the individual infantryman to deliver precision fire to an enemy, and bursts of automatic fire if necessary for maneuver (though not for the duration that a light machine gun would deliver).