I shot at least 10,000 of the older nickel plated WSR and they worked fine. Then in 2000 Winchester came out with the brass finish primers. I called and Winchester told me they had made these primers more sensitive.
Loads that never bothered the old nickel plated WSR pierced terribly with the brass finish WSR. Soon I had a handful of dished AR15 firing pins. I am using a couple of them as punches. I cut the loads, and cut the loads, and about 1.5 grains down the primers stopped piercing. Since I wanted more velocity than I could get out of these brass WSR, I just loaded close range ammunition with the brass primers and used my CCi #41’s at long range. I am close to the last of the brass WSR; I loaded up the last with FMJ’s for rock busting and used reduced loads.
The primers go bang, they are accurate, but you cannot push bullets as fast as you can with CCI #41’s.
Even though I had a standing slamfire with a brass WSR I am not as worried about AR15 slamfires as I am with Garands/M1a’s. I have never heard of an out of battery slamfire with an AR15 action and I believe it is because the firing pin in an AR15 only extends during cam down, when the lugs are in engagement, thus slamfires will always be in battery. For Garands/M1a’s/Mini 14’s/M1 carbines, the firing pin is only retracted on cam down, and there are many accounts of these weapons slamfiring both in battery and out of battery with sensitive primers.
If I'm not shooting, I'm reloading.