The Remington 7 1/2 primer has a thick cup, preventing it from being pierced when shooting high pressure loads. I have used it with BL C2 in a 222 Remington and got excellent groups. Also in 223 with great results. I use it in every thing from 221 Fire Ball through the 223. I have yet to have a pierced primer and they shoot tiny groups. Of course I do not over load my rounds, but I have not had ignition trouble, no matter what powder I was using. Remington first developed the 7 1/2 for the 17 Remington when they were experiencing pierced primers with their regular primers. Unfortunately, these are difficult to get right now. I have just bought Wolf primers - they make 3 different ones for small rifle. I bought the one with a thick cup and regular primer compound. I think it is a 223M. It is not their magnum, they have one of those too. I have not had a chance to develop any loads with them yet, so I can not report as to their reliability or accuracy. They do have a good reputation, however.