ORIGINAL: stubblejumper
The magnum primers will decrease the effective burn time and increase velocity. I gain over 100 fps in my 06 when switching from 210 to 215 primers with 180 grain bullets. This should work in any case capacity limited cartridge.
Of course the extra velocity is a result of extra chamber pressure produced when using the 215s.You can simply use 210 primers,and add a grain or two of powder to achieve the same results.
I guess I misunderstood the posts above. I understood the problem with 4350 in the 308 was that it reached max case capacity before it reached rated pressure and there was no room to add a grain or two of powder as you suggested. That is also why I specified "case capacity limited cartrigde" in my post above. RL22 in my 06 required heavy compression in order to get good velocities with some bullets. When I switched to the 215 primers I got the desired pressures without heavy compression of the powder. I dont load for the 308 but it seemed to me like the same situation for Shoulder Strap.