Abstract: A hammer assembly for a side hammer percussion lock is comprised of a hammer which is displaceable relative to the firearm from its normal operative position to a safety position where it cannot be brought into contact with a percussion cap placed on the firearm. In one embodiment of the invention the hammer is displaced by rotating it about an axis which is perpendicular to the axis about which the hammer is rotated between its cocked and firing positions. In another embodiment of the invention the hammer is displaced to its safety position by being slidably translated relative to the firearm. In the rotating embodiment, detents are provided for fixing the hammer against inadvertent movement from its desired position. In the sliding embodiment a lock is provided to prevent movement of the hammer from either its normal or safety position without first releasing the lock. A cam is provided in both embodiments to lift the hammer slightly off of the percussion cap when it is moved out of its normal position.