How to Fix a Loose Hammer on a Percussion Lock

A muzzle-loading firearm and the successor to the flintlock, the percussion lock uses a cap that fits over the head of the hammer to ignite a black powder charge. Because of the design, the hammer of a percussion lock can work loose with continued firing. If addressed immediately, a loose hammer can often be repaired by tightening or replacing the tumbler screw that holds the hammer to the lock plate; if neglected, both the hammer and tumbler screw will almost always require replacement.

Things You'll Need

  • Precession screwdriver set
  • Vise grip pliers
  • Duct tape
  • Thread sealer
  • New tumbler screw
  • New hammer
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Instructions

    • 1

      Place the hammer in the "uncocked" or fully forward position. Remove the hammer-side lock plate from the firearm with a set of precision screwdrivers.

    • 2

      Cover the jaws of a pair of vise grip pliers a with duct tape. Grasp the cap on the back side of the lock plate, at the base of the tumbler screw, with the vise grips; remove the hammer's tumbler screw from the lock plate with a screwdriver. On some models, the tumbler screw will come free from the lock plate without needing to hold the cap with the piers.

    • 3

      Examine the shaft and threads of the tumbler screw for signs of wear, which is the most common cause of a loose hammer on a black powder firearm. Examine the inside of the tumbler screw hole on the hammer for signs of reaming. If neither the hammer nor screw show signs of wear, apply thread sealer to the threads of the tumbler screw and replace the hammer and screw. Do not allow sealer to get on the shaft of the tumbler screw, above the threads, as it will impede the movement of the hammer.

    • 4

      Install only a new tumbler screw if the inside of the hole in the hammer does not show signs of damage. If the inside of the tumbler screw hole does indicate wear, replace both the screw and hammer. Take the worn parts to a gun shop to have them matched up with new parts or order OEM -- original equipment manufacturer -- parts online.

    • 5

      Apply thread sealer to the threads of the new tumbler screw. Install the new tumbler screw and hammer in the lock plate. Reinstall the lock plate on the firearm.