I don't know the answer to that. Many people use Winchester White Box. I am not crazy about it because I don't like squared off bullets because they chamber kinda hard. I have used quite a bit of PMC without issue. I did not read your other post yet, but after a thorough clean and lube rack it over and over, 100 times or more and shoot it some more. If you still have issues give them a call at Ruger.