Abstract: A nail and dimpler driving apparatus for a nailing gun is provided having a barrel with a short hardened metal dimpler which slides longitudinally in the end of the barrel and comprises a hardened metal piston having a broadened face at its end extending symmetrically on opposite sides of a metal plunger which extends longitudinally from the lower center of the piston face in alignment with an orifice through the dimpler. The piston reciprocates to impact a shoulder at the inner end of the dimpler. The barrel has a longitudinal rail extending along the top of its bore to maintain the piston and dimpler in angular alignment and to guide nails fed into the bore from an opening located in the side of the barrel between the tip of the retracted plunger and the dimpler shoulder. The rail has a longitudinal groove in its lower edge to aid in guiding the nails and in providing clearance for the residue of web material used to join the nails in flexible collated strips.