. I think the humidity is a big factor.
OH YA !
It get's nasty here in Minn too.
What if I drilled out the flash channel and re-threaded the clean-out plug hole?
Na, just pick the nip from time ta time,,If I'm in a aggregate shoot or session and I get just a little hang fire,,I'll pull the nip and brush it well (little brass brush from NAPA-$3) get the bottom of it too. I've found the cap fouling is worse than the powder in the flash channel. Point is the flash channel is big enough,, the fouling happens in the nip,, I keep small sections of pipe cleaners handy too for inside the nipple