This is a shame, as Winchester primers are one of the most easily obtained brands around here. I've got a bunch of them, but have not had any problems. Gonna check the lot numbers on the ones I have squirreled away.

Years ago I had the exact same problems with a particular lot of Remington LR primers. I had just started reloading (for a 6.5 Arisaka, coincidentally) and I was blaming myself for doing something wrong but had no idea what. Fortunately I saw an announcement in a magazine (WAY before Al Gore invented the internet)concerning the piercing problem with Remington primers. I contacted Remington and they sent me a whole carton to replace the 200 primers I had purchased. No problems since, and I think I'm still using primers out of that carton.

Pierce primers in my ARs and Mini14, but not the 5.56. The latter seem to do fine but loads like the. 64 grain Winchester, Razorback (very accurate in a couple of my rifles by the way), and 55 grain soft points. Only happens with Winchester 223. All other ammo I've run through my AR's including handloads do fine with no pierced primers.