I have a pair of 1851 Navy revolvers that were notorious for cap jams. One is an old Armi San Marcos made gun and the other is made by Pietta. I recently equipped them with aftermarket nipples made by Slix Shot. These nipples have a re-designed combustion chamber and two lateral vent holes in the cone. That relieves the back-pressure from the exploding charge of powder in the revolver’s chamber. It cured the cap jams in these two guns.