Hi,
I have been involved in reenactments in the pouring rain, one in particular this past summer at Hastings, Michigan. I mean it was a complete downpour. I continued loading and firing my rifle (just blanks of course,
) through the entire event as did the rest of our boys in blue and those in gray on the other side. No one it seems had any problems whatsover. We kept biting cartridges and just pouring it down the barrel and it would fire everytime. The nice things was the rain was helping cool our barrels and that was a bonus for our hands!
It was really one of the cooler events I've been involved in. The rain and wet air knocked all the powder smoke down to the ground and it was really something to watch a volley and then watch all the smoke go down and spread along the ground instead of it's usual blowing away.
Dispelled alot of myths in mind about rain and blackpowder. There are many accounts of troops fighting in downpours and thunderstorms during the Civil War and obviously it didn't have too much effect as long as your cartridges stayed dry in your box or you didn't somehow like pour water down your barrel off the rim of your hat or something.
The battle of Chantilly right after Second Bull Run was fought in a violent thunderstorm and downpour. Men were firing at each other by the lightning flashes.
And by the way, wet wool dryed out in the sun after a downpour tends to uh, shrink. Big time. Learned that lesson for the first and last time. Hehe.