Generally I choose a primer, standard or magnum, based on the powder I am starting with. Using a flake or ball powder I generally run with a CCI 450 magnum primer (748, H414, H335, H380, and BL-C(2) for example), when starting with a stick powder I run with the CCI 400 standard primer. Basically this works for me in several rifles from AR to bolt.
The following were 10 shots over the chronograph. The loads were all H335 26.1 grains in LC 11 brass pushing a 53 grain Sierra BTHP match bullet. The rifle was my modified Rem 700 with a slow 1:12 twist.
View attachment 1020994
While all the 10 shot groups weren't bad the best group came from the CCI #41. The worst group was the BR 4. Since I was more concerned with getting them all over the chronograph the group sizes are subjective.
Load some, shoot some and see what works for you with your powder.
Ron