The 777 is absolutely not corrosive . The Pyrodex on the other hand is very corrosive , more so in my opinion than real black powder . My dad was a fan of the 777 , I shoot real black mostly . You can always throw 10 grains of black First and then the rest of your charge in 777 . Let the black light the sub . I have done this with a flint gun and Pyrodex back before I figured out that it was not something I wanted to be shooting anyway . I found a closeout at Walmart one year after hunting season and bought 15 pounds at $5.00 per pound so I had to try it . Gave most of it to a guy I really didn't like much .
Eddie