Thanks guys. It may very well take #10 caps. I just assumed #11 caps as the nipple looked similar to the one on modern muzzle loaders.

I guess I will tell him to try to find a gunsmith to check it out. Unfortunately all of them either of us have dealt with in this area are pretty bad and tend to not do very quality work. Does this sound like something that could be fixed if he was to find a decent gunsmith, or are they pretty much worn out once the cylinder gets play in it?