Abstract: A full automatic firearm or submachine gun has a combined trigger, sear and selector mechanism including automatic and semi-automatic bars which are pivoted at their forward end to the trigger, and a sear member disposed therebetween and independently pivotably mounted. A selector member is pivotable among safe, semi-automatic and full automatic fire positions, and is engageable with the bars to effect their pivotal movement as required and is engageable with the sear to prevent its movement in the safe position. The semi-automatic bar, automatic bar and sear have means which are engageable to pivot the sear from engagement with the bolt upon pulling of the trigger, but only one bar is so engaged at any one time. Biasing means bias the sear, semi-automatic bar, automatic bar and trigger to their respective initial or at rest positions.