the strongest of caps? Heard Chuck Dixon explain once that standard caps were good enough for everything for a century plus. Then when the first substitutes came out, the caps had trouble igniting Golden powder and Pyroduh, so then "MAGNUM" caps hit the market. So soon most generic gun shops were carrying only the hotter caps and not standard caps. Because of magnum caps some cap manufacturers altered their nipple structure. So then we have standard caps which worked fine historically in standard nipples., then we get magnum caps and nipples that are altered for magnum caps and we have bigger chance of problems from caps. His explanation is that caps always fell into colt revelover mechanisms, but it happened with increased frequency with magnum caps, and then all kinds of gimmick nipples came about, with holes drilled through the sides etc.
Now we have dumbed down musket caps and re enactor powder and 209 primers to further confuse the mix for reliable ignition. More kinds of fake powder, and the numerical number of miss-combined factors for misfires increases. Chuck also had an explanation for how nipples changed, and something about the flash hole in the base for standard caps being extremely small, to prevent back pressure.
So I and another guy simply purchased "standard" caps for our cap and ball revolvers. In my ruger and 1860 colt from Euro arms, I never had increases misfire problem with standard caps. I also never switched nipples.
Just passing along what the Grand Oracle of Black Powder said about the issue.