A crud ring is nothing more then fowling of the powder in the barrel of the rifle near the area where the projectile sits. All powders produce a crud ring of sorts. Some powders perhaps worse then others. The difference in the crud ring that concerns black powder shooters is how hard the crud ring is.

Triple Se7en fowling is crusty and much harder then other powders. Since it is made from the burning of Triple Se7en it can be removed with simple water. So when you swab the bore of the rifle you have to pay special attention to the area near the breech. Work the barrel from the muzzle to the breech in short strokes with your cleaning patches and you should be fine.

Pyrodex produces a softer fowling then Triple Se7en but it is still fowling just the same and should be swabbed between shots for the best accuracy from your rifle.

Goex also produces fowling and again it can also be removed with a simple swabbing of the bore. The Black Mag3 I can not comment on. Clean Shot or AAP produces a fowling but not to the degree of some of the other powders.

No matter what powder you pick, be sure and carefully swab between shots and do not worry about the crud ring. Make sure you put a witness mark on your ramrod and that each projectile you load falls to the witness mark. If you're doing a good job of swabbing the dreaded crud ring will not be a problem....