Considering that pewter was cast, and formed, into all kinds of dinnerware, and utensils, very early in our history, it's only logical that gunsmiths used it as well. I'm sure it didn't take the smiths of old long to find new ways to utilize damaged plates, flagons, and utensils. I would suspect that pewter was quite likely used more in areas where factory produced sheet metal was harder to obtain, i.e. the south.
Hungry Horse