A surgical instrument for use in connection with a pneumatically powered tool having a firing mechanism operably supported therein that is movable between an unactuated position and an actuated position. In various embodiments, a drive system is supported by at least one of a handle assembly and an elongate shaft assembly and is configured to selectively apply a firing motion to the firing mechanism of the pneumatically powered tool to cause the firing mechanism to move from the unactuated position to the actuated position in response to a flow of gas from a source of gas fluidically coupled to the drive system. A travel monitoring member is operably supported by the handle assembly and is linked to the drive system to provide an indication of progress of the firing mechanism of the pneumatically powered tool as the firing mechanism moves from the unactuated position to the actuated position.