A surgical stapler having a distal end to which is mounted a tool assembly having a pair of opposing tissue engaging surfaces for deforming a plurality of surgical fasteners through and fasten tissue, the surgical stapler comprising: a housing having a fixed handle； a clamping handle mounted to said housing and selectively movable relative to said fixed handle from a first position in spaced relation relative to said fixed handle to a second position closer to said fixed handle to actuate the clamping of tissue； a lead screw to actuate the tool assembly to clamp tissue； a drive assembly including a shaft, said shaft being mechanically engaged with said lead screw such that upon selective activation of said drive assembly, said shaft rotates said lead screw to advance a roll nut distally along said lead screw to force a firing piston into the tool assembly to deform the surgical fasteners through and fastening the tissue； and wherein said drive assembly is selectively variable to regulate the advancement of said roll nut along said lead screw which, in turn, regulates the speed at which said surgical fasteners are deformed.
