I have been using winchester primers in my XL650 and loaded several thousand rounds now. I get a flipped primer like 1 out of every 300.

Tried some Federal Magnum match primers for some hot 45 acp loads I was doing. I got almost 10 upside down primers in only 50 rounds. That was with me catching the problem quickly and inspecting the primer before seating... I think they were flipping in the primer system as well as during the primer seating process... I thought my press was the problem but I switched back to winchester right after and had no problems.

I suspect that the Federal primers have a rounded edge than the Winchester. And it is possible that the press is slightly out of time. Just enough to mess with the Federal primers but not enough to mess with the Winchester.

I just deprime them slowly and reuse them after inspecting them.

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