try real black powder…. 777 is hard to set off
The powder isn’t the issue here. I’ve fired many shots out of my GPR with 777 and various #11 caps and never had an issue igniting it. This includes days of being loaded in hunting situations. With a properly cleaned gun, it’s not hard to set off at all. Seems like there is a fouling or obstruction issue as others have described. I do shoot real black powder out of my flintlock.
turtle2, are the caps going off each time but not the charge? Other than what others have said, which are likely solutions, consider:
Bad CCI caps. It happened to me. CCI had a few specific lots that did not dry/cure properly. If it takes a few hits to get the cap to go off, contact CCI with the lot number and they’ll refund.
Flared nipple from repeated use has made it difficult to get the cap to seat but not sure it would keep it from going off.
Put the factory (or new OEM) nipple back on. I tried a white hot and had better results with the factory nipple.
If you use anti seize grease on the nipple threads, be very careful not to use get any near the hole on the bottom of the nipple.
Clean the flash hole well with a small pipe cleaner. I put a slight bend at the end and a little finesse to get it in as far as I can. For the first few, I dip them in blue thunder from October Country, then several dry ones.
Others mentioned it but you need a fouling scraper and jag sized for the patent breech to keep it clean.
Pop several caps on the unloaded gun with some shredded paper, etc. near the muzzle to see if you’re getting movement, e.g. clear path. Always pop a few caps before loading for the first time on an outing.