I know they had to have happened, especially with inexperienced gunners, but I'm having trouble hunting out how they work, exactly. While I'm sure they would be concentrated on the hands, I'm assuming the face and neck would get spattered with powder as well. But I don't know.
Plugging "gunpowder burn" into Google gets me plenty of hits related to ballistics, which is fantastic, but unfortunately it mostly relates to modern firearms. "Powder burn" gets some really interesting hits on how quickly the powder burns, but is still not what I need. (It also finds some metalcore band from Texas, which is awesome, but useless.)
I thought "flash burn" might do the trick, but that's apparently a different kind of burn entirely. Oops.
So basically, what I'm looking for is this: What constitutes a powder burn, what causes it (aside from the obvious answer, gunpowder), how severe would it be, and where in the world is the powder and other debris going? Also, would that sort of burn come only from a misfire or backfire, or could they form in the course of repeated, rapid firing and reloading?
I'm also looking for information on guns backfiring. In movies, it's shown as a dramatic thing that usually causes the shooter severe injury. (The Tom Cruise movie Far and Away is a good example.) However, when I look for "gun backfire", "firearm backfire", "backfire" or even "blowback", the best I get in return is information on gun laws. I have the information I need on misfires and premature discharges, it's backfires that have me stumbling.
Thank you to everyone who responded! I think I've got a better idea of what I'm looking for now!