A loading unit (20) for a surgical stapling device has a cartridge assembly (508) and an anvil assembly (506), the cartridge assembly including a channel (516) and a staple cartridge having a plurality of surgical staples (530) therein. An axial drive assembly (560) has a clamping member (606), the clamping member having an upper flange (606b) for engaging the anvil assembly, and a lower flange (606c) for engaging the channel. The axial drive assembly is movable through the staple cartridge to drive the staples out of the staple cartridge and against the anvil assembly. Mechanical features (1020) are defined in the channel for indicating an end of stroke for the axial drive assembly, the mechanical features having a first pattern (1020a) and a second pattern (1020b).
