Red,
I think it is caused by the 209 primer. A lot of folks using Omegas and Encores have switched to a .25 acp conversion. This doesn't burn as hot so no crud ring. Precision Rifle makes them and you can see them at
www.prbullet.com I have one but haven't really given it a go. I'm using BlackMag3 powder and the Precision rifle Dead center Sabot now. The BM3 burns so clean I don't have to clean my gun until I'm done shooting.