Abstract: A handgun of the drop barrel type has an over-length firing pin coupled with a "pile-driving" barrel action that permits the firing of rifle load cartridges. A micro-precision timing sequence of the action causes the rearwardly propelled cartridge disposed in the floating drop barrel chamber to strike the fixed firing pin while the barrel is still in its rearwardly moving direction. In the preferred form of the invention a spring driven actuator sleeve surrounding the barrel interiorly of a receiver tube propels the barrel rearwardly such that the cartridge is ignited and the bullet discharges from the barrel prior to the seating of the barrel against a breech plate that is integral with the gun frame. Gases escaping and expanding from the cartridge are captured by the barrel and actuator sleeve and cooperate with the inertia created by the falling barrel to lock and seal the barrel chamber against the breech plate.