The question of caps is always an an interesting one. Each time I acquire a new "Toy" and yeah for those of you that will troll that answer guns=weapons=not toys; to which I say What Ever!
Sorry, I digress.
Where was I? Oh yeah, caps! I find my self each time trying out what cap fits that nipple right and snug. Just putting them on at home wont give the answer. You have to fire a live round or 6 to see what hangs on during the big bang. Please don't "Squeeze or pinch your caps on the nipple. If you find yourself doing this, you indeed have the wrong size. Just because its a Pietta made 1858 Remington or 1851 Navy doesn't mean it will automatically just take a Remington #11 cap and work. Your gun may only like a CCI #10 and hate the Winchester #10. ( Unless its a Colt, it just hates everything equally. )
Summary of this rambling is this, go out and get a few different brands, try them out. Essentially play with them ( The grown up term would be to experiment, again I digress
)
till you find what works for your toy and then go enjoy it. By the way keep the other caps around, they come in hand for that next new "Toy" that needs experimenting to get that right fit.
Happy shooting.
Pete