Try Black powder. Its pretty consistant and accurate as well. I have a TC Pennsylvania Hunter that I load with 75 gr FFF under a home cast .495" lead ball, seated in a .015" patch, lubed with Natrural lube 1000+. I set it off with CCI Magnum #11's. It will shoot 1" or under @ 100 yards from a bench.
I had a TC New Englander that would shoot 2" groups with TC Maxi Balls and 75gr Goex FF, Set off with CCI #11 Magnum caps. Traded it for a bow.
None of my rifles EVER hang fire or are hard to clean. They were seasoned with Goex BP from the start. Alot of old time BP shooters will tell you, The more you shoot with BP the easyer it gets to clean.
My flintlocks always go BOOM as well, Even in the rain.
Alittle forthought and preperation and any smoke pole will function fine.