A surgical fastener applying apparatus includes an end effector assemblyhaving an anvilassembly and a cartridge assembly. The anvil assembly and/or the cartridgeassembly ismovable relative to the other between open and closed positions. The cartridgeassembly isconfigured to retain a plurality of surgical fasteners therein. A fluid-actuated drive assemblyincluding a distal piston member is configured to oscillate between proximaland distal positions.The distal piston member includes a base and a rack extending distally fromthe base andslidably disposed within the cartridge assembly. A drive beam is configuredfor translationthrough the cartridge assembly to eject the surgical fasteners from thecartridge assembly. Apawl assembly couples the drive beam to the rack such that the drive beam isincrementallyadvanced along the rack and through the cartridge assembly as the distalpiston memberoscillates between the proximal position and the distal position.
