The HJS derringer has four two-inch rifled barrels drilled into a single piece of steel. A lug on the bottom of the four barrels fits into a slot in the frame. The barrels are held in the frame by a latch mechanism that is nearly identical to that of the 1859 Sharps derringer, with a release button on the bottom of the frame. The hammer is tensioned by a flat spring in the grip. The hammer features a rotating firing pin originally patented by Christian Sharps in 1859--each time the hammer is cocked a pawl rotates the firing pin 90°.