My hunterbolt mag gets a lot of blowback with the .50 barrel and very little with the .45. I'm using W 209's and 100gr of 777, but the dreaded crud ring isn't much at all. I can feel it when I run a spit patch after each shot, but no sense of a deposit when I follow it with a dry patch.
Off the subject a bit, I found that my 260 platimums, Winchester that is, hit the same point of impact as my 250 grain Barnes MZ's with 100 grains of 777. 1-2 inch groups for both which will make practicing cheaper. I'm hoping they stay the same out to 200 yards, which will be sick.