Ok, here's a lesson learned, albeit belatedly. I've been hand loading since before a lot of you guys were born - and it's not too late for me to realize I should have been doing something a different way. So, maybe this thing that just bit me won't bite any of you guys after you read this! I keep pretty good reloading records and have done so since the late 1960s. I keep track of all the stuff most of you guys do, of course. The ONE thing I have never tracked is the lot number of my primers. I have just never bothered. Up until now, I've never had a problem with any primer. Fast forward to now. I had what appeared to be maybe 4 primer failures in one range trip, Tiny little pinholes in the "gap" between the primer cup and the side of the primer pocket, with some burned powder residue evident. Looking at the bolt face of my Sako .243, I had a nice erosion ring in a circle pattern the same diameter as the primer pocket. Serious erosion, but likely not dangerous. I punched the primers out (kept them) cut open the cases so I could look at the primer pockets, and also ran all the components through an ultrasonic cleaner to get a better look. The primer cups had small pinholes along the outer edge where the sides round over to the primer's face. I sent a note to Winchester and they asked to see them, despite the fact that I had no lot number to give them. Winchester verified that the primer cups had failed. They offered to send me new primers for the ones I had to punch out, but I'd need to send them the ones I punched... kind of a hassle and not really worth the time. They didn't have to offer though, and it's good of them to do so. Bottom line: I have probably 2,000 large rifle cartridges with Winchester primers in them and no lot numbers recorded. I have a ruined bolt in a very nice Sako .243 and a replacement bolt just cost me $394. I had to have a gunsmith adjust my headspace. (it's an old Sako... not easy to find a bolt, but I did) I have to disassemble all of the Winchester primed cartridges I have loaded and then test the open bricks that I have on hand, to see if there are any bad lots. Then I'll be reloading the pulled bullets, which is not what any of us like to do. This is not a fun thing. If I had known the lot number, I'd know exactly which primers to punch out, and Winchester could have recalled them, and then replaced them... saving me, and maybe you from future problems. Have fun out there... and keep all the records you can.