A bolt carrier for a firearm, including lugs on the first end to engage corresponding lugs of a barrel receiver/extension. The bolt carrier includes a cam slot within which a cam pin from a bolt is constrained to travel along a cam slot path during rotational and translational movement of the bolt. The cam slot defines (1) a first cam slot means for constraining motion of the cam pin and the bolt during engagement or disengagement of the lugs of the bolt and the corresponding lugs of the barrel receiver or extension; (2) a second cam slot means for imparting rotational movement to the cam pin and bolt during linear movement of the bolt carrier; and (3) a third cam slot means for constraining motion of the cam pin at an end of a rearward travel of the bolt and bolt carrier during an ejection cycle. The combination of the first, second, and third cam slot means yields an extension of the unlocking by over 10% and a delay of the actual unlock of the bolt by over 5% relative to TDP.