RE: Wet powder, no buck!!
 

I had something similar happen on a bear hunt. I have a cow elk muzzleloader hunt coming up soon during the "wet" season, and I picked up a kit at the sporting good store. It has the finger cots to put over the muzzle and a plastic ring that holds and seals a cap to the nipple. My hunting buddy recommended to fire at least two caps before you load to burn off any moisture/oil in the barrel, load, then pull the nipple and add a wee bit of powder there. This is for traditional open breach caplock rifles, not sure if you can do it on an inline.

RE: Wet powder, no buck!!
 

Nope!! This has never happened to me. I put plastic wrap around the muzzle and over the lock area when hunting in the rain, and carry the rifle muzzle-down with the lock area under my left armpit.

Ionce hunted for a week in the rain in the Adirondacks carrying a caplock rifle so protectred, loaded all week, and on the last day, I unwrapped the lock, cocked it, and shot at a target 75 yards away. Dead on the correct spot, 2" high.... This with Clean Shot (same as APP) for the propellant..... Left the gun in a truck every night after removing the cap. Replaced the cap and re-wrapped the lock section every AM, under a tree where there was protection from the rain while recapping.

Inlines should be a lot easier to waterproof than a sidelock!