A shell loading system for a firearm in one embodiment includes a barrel, receiver, reciprocating slide and bolt assembly, tubular magazine, tilting carrier operable to receive and feed shells from the magazine into the action, a spring-biased carrier latch laterally moveable to engage the carrier, and a pawl pivotably mounted on the carrier. A carrier latch disconnect is movable between an unblocking and blocking position that prevents engagement of the carrier latch with carrier. To prevent bouncing of the carrier after firing a shot, a first detent feature on carrier assembly automatically engages a second detent feature in the receiver as the carrier returns downward from an upward position when the action is cycled by discharging the firearm. The detent features automatically disengage when the slide moves rearward to permit normal operation of the carrier when cycling the action.