oldwun
I do have one that I purchased from PR - kinda expensive, but for me it was worth it - only because it stopped the blowback into the firing pin area and what use to go up against the scope. I did not find any difference in accuracy, and I really can not say that it did anything for the "crud ring" cause I get so little of it anyway...
The second & third ones that i have I took to my local machinist and he drill them out from the pattern that I provided him.