I've only used Musket caps in my Navy Arms Zouave "that I used to have" in everything else I use Remington #11 caps.
My little CVA Bobcat .50 shoots pretty well but when I experimented with 777 FFF I would occasionally get misfires till I learned how to load 777 FFF properly, now every time I load it with anything but Pyrodex RS "it doesn't like the larger granules in it's smallish flash channel" it goes BOOM when I squeeze the trigger.
I've learned from my N-SSA days that FFFG was the way to go, cleaner burning than FFG & a bit more accurate at the range & in keeping that tradition for my hunting rifles & ofcorse my revolvers I rarely have an ignition problem unless I did something wrong in my process of loading, the same goes for Pyrodex P, I've had very reliable ignition with Pyrodex P even in very damp weather while hunting.
I take my rifles that I plan to hunt with & swab them with 91% rubbing alcohol to get any moisture & oils out then dry patches "I cheat & use my Bore Scope to make sure that I did get everything dry before I pour any powder in the muzzle."
Pour my measured amount of powder then I'll bump the side of the barrel a couple of times to settle the powder into the firing chamber, my PRB home then I'll swab the bore above the PRB with a Crisco lubed patch "not a lot goes onto the bore but enough to keep from any moisture from attacking the bore" then a strip of Electrical tape over the muzzle to help keep moisture & junk out of the bore "seems t help."
While the rifle is loaded I'll keep either my rubber vacuum cap onto the nipple or a #11 Remington cap in place with some bees wax surrounding the two, but never do I not have something over the nipple that'll allow moisture into that area.
I've had my rifle soaking wet, cold enough to see sweat freeze on the outside & once when I had taken it in to shoot at the range the next day sweat all over the outside of the barrel but "knock on wood" I have yet to have a misfire or hangfire since I started doing what I do during the loading process &/or daily routines while they are loaded.
BTW I've had my C&B revolvers at one time or another loaded for up to a year & would get caught in the rain with them on my side, take them in & out in the coldest wettest days to check traps or do some scouting & have never left any of them in the truck because it's cold out but in the 25+ years of doing so have never had one not fire it's 5 chambers as reliably & with the same authority as if I had loaded it that day, I think my success is from what I do in the loading process, & what I do to help prevent moisture from getting into the loaded chambers or bore of the loaded weapon.