Inserts, splines, and methods for reducing and/or eliminating spline crash in surgical instruments

Inserts and features to reduce or prevent spline crash in surgical staplers and/or to minimize damage resulting from spline crash in surgical staplers. An insert for a surgical stapler includes a body and spline covers. The body is configured to fit within a bore of a shell assembly and the spline covers extend inward from the body. Each of the spline covers are sized and dimensioned to cap a distal portion of splines of the shell assembly. A shell assembly for a surgical stapler includes shell splines that are disposed on an inner wall of an inner housing portion that defines a bore. The shell splines include a lead spline that has a leading end positioned distal of a leading end of each of the other shell splines.