During the attack in the King's chambers at the end of the movie, a muzzle-loaded pistol that has already been fired is discarded in the melee. A short time later, the King picks it up and fires it again, though it has not been reloaded.
As the soldiers arrive to attack the abbey, the rebels run out and one rebel leading the others is carrying a muzzle-loaded pistol and fires it toward the soldiers. He fires one time, with an accompanying muzzle flash and sound, but the sound of another shot immediately follows the first, with no other muzzle flash or visible person holding a pistol. Two shots, with only one muzzle flash and one person holding a muzzle-loader, clearly the sound o a shot was dubbed in.