Originally Posted by Dan Carey
CCI and Federal primer are used by a lot of BR guys. I use Rem 7 1/2 BR primers in all my small rifle primer loads and that includes my 38 super pistol. I've tried them all in the 38 years of competition shooting and don't see a difference in any of them. The last time I bought SR primers I got Winchester the cheapest and bought 15,000 of them. But I still use Rem in the BR guns.
I like the Rem 7 1/2 BR primers too, for certain applications.
I am not able to see much difference in large rifle primers, but in my 223, 204 and 17 rifles, primers seem to make a difference.
In my 223 the slight edge goes to the Rem 7 1/2 BR primers.
In the 17 and 204 my groups tightened significantly using the Rem 7 1/2 BR primer.
I would borrow some different primers from some reloading buddies and try them out with the powder you are using and see how they do.
As far as temperature is concerned, I think the powder will have more of an effect on your velocity than the primers do, all other conditions being the same.
I have shot my 223 at 10 below up to over 100 and the primers worked fine. It was the powder that tended to vary the velocity.