Thread: CCI BR4 vs CCI 400 primer’s

The BR4 and 450s have thicker and harder cups that are supposed to be more pressure tollerant, hence the 450s being called magnum primers (BR4s are supposedly the same as the 450s just more betterer).
You aren't supposed to use the 400s in semis as they are reportedly prone to slam fires, either match or magnum primers are considered safe to use.

As to why your Tikka has issue with BR4s? No idea but I was about to try a similar test with my T3 223, BR4s vs 400s with 75gr bullets.
I've never had a primer issue with mine but I have never specifiaclly tried the thicker primers either.