For my sons' 1858 Remingtons, one in .36 and one in .44, I've been buying them #11 caps. It appears that unless I replace those with #10 caps, they're risking a nipple-end chainfire? Is it the extra brisance of the #11 cap that's the culprit?
They each have several hundred WonderWads of the appropriate caliber, and well-lubed conicals, so I'm not too worried about the chainfire starting from that end.