I had a european made repro percussion gun that didn't line the hammer up with the nipple well at all. I used marking die on the top edge of the nipple to show me where the high spots were on the hammer, then used a dremel tool and grinding bit to remove the high spots. Kept testing until the hammer cut a nice " donut " like a paper punch, on a new nipple. Solved the stuck caps in the hammer issue by using a triangle file to file open a relief in the front edge of the hammer skirt. This allows the gases to blow the cap open towards the front of the gun, away from my eyes, which released the caps so they could fall off the nipple, or hammer, when I cocked the gun after firing. Uncle Mike's " HOT-SHOT" nipples were designed to accomplish the same thing, by providing a port for gases to hit the edge of the cap and blow it out, breaking any seal that may occur between the cap and nipple, or in you case, with the hammer skirt.