RE: Wet powder, no buck!!
If you did not like Pyrodex then I would try some 777 pellets. They are cleaner, less smoke and no sulphur smell. If you experience the dreaded crud ring then your only alternative is go back to the Pyrodex in pelletized. If you want to shoot loose you can look at Mag 3, a clean/ more potent sub with no crud ring...so an alternative if you will to 777.
As stated all powder is suspect to drawing moisture, so make sure you take ever precaution to weatherproofing your ML first and foremost. Cover the barrel, keep it clean & dry and possibly cover the breech or nipple area in rain in some manner.
I have absolutely no experience with Pionner Powder so I can not compare it to others I have used. My experience with pellets isonly with Pyrodex and 777,at that it is very limited, as I prefer the benefits of shooting loose.
Good Luck