I don't know what you are referring to "crud ring" but I'll tell you something about T7, I used that stuff in my TC Hawken 54, same charge I used with pyrodex and broke the stock in half, after the smoke cleared I was holding the pistol grip and butt in one hand and the rest in the other !!
I sent it to TC and they replaced it for free and told me never to use that stuff again in that gun.
Check out what the manufacturer recommends for your gun before you load it, Just a word of caution !!
What is a "crud ring" is that the ring around your mouth after you eat a chocolate popsicle ??