I use the cream of wheat method to fire form my 470 Mbogo...It works and I hate the mess it creates.
My buddy has a place in the country so we decided to shoot off the FF loads (20 grains WW231/full case of COW/topped with toilet paper wadding) in his garage. The sound was deafening, the snow storm blinding, the stink nasty, and the dent in his garage door unmistakable!
I made the mistake of pointing it at his metal garage door and from the outside it looked like the roadrunner hit it!
After discussions about how much a new garage door was going to cost me we took the remaining COW loads outside