Combat rifles fall into two families, differentiated mostly by their magazines: combat rifles proper, sometimes called burst-fire combat rifles, and machine guns (sometimes called support machine guns) capable of fully automatic fire. Operationally, the two families differ strongly. Combat rifles have smaller magazines that reload more quickly, firing a short burst of shots with each fire command, while machine guns have larger magazines that reload more slowly, firing continuously. Other than magazines, the two families share most parts, though certain accessories are specific to one or the other, and there are also certain family-specific bodies, sights, and stocks.