A surgical end effector comprising a cartridge jaw is disclosed. The cartridge jaw comprises a proximal channel portion extending along a longitudinal axis, and a distal portion movable relative to the proximal channel portion between an open position and a closed position. The surgical end effector further comprising a staple cartridge removably seated in the cartridge jaw, wherein the staple cartridge is configured to slide along the longitudinal axis into the proximal channel portion of the cartridge jaw when the distal portion is in the open position.