A shell assembly for use with a surgical instrument, the shell assembly comprising:a shell (31, 110, 180, 210) including a ramp (37) and a locking aperture (36, 126, 182)a staple guide (60, 140, 170, 230) configured to house a plurality of staples andat least one engagement structure disposed on the staple guide, the at least one engagement structure including a surface configured to slidably contact the ramp of the shell prior to the at least one engagement structure engaging the locking aperture.
