A surgical severing and stapling instrument clamps tissue within an end effector of an elongate channel pivotally opposed by an anvil. An E-beam firing bar affirmatively maintains a desired spacing while severing and stapling tissue by longitudinally engaging the anvil and elongate channel. Separate closing action and firing (i.e., severing and stapling) action of the end effector allows a clinician to selectively position and clamp tissue. The end effector enables this advantageous separate firing while affirmatively spacing the end effector by having an upper pin of the firing bar reside within an anvil pocket before firing. When the anvil is closed and clamped, the upper pin of the E-beam firing bar may move longitudinally and distally from the anvil pocket to an anvil slot thereby engaging the anvil.