300 WSM primers?

[M700]

Have run into a variety of different recommended primers for the .300 WSM in the published and on-line load data from different powder & bullet makers.

It's certainly not a huge case... What's working? Standard primers? Magnum primers?

This cartridge is new to me...

Thanks, Guy

 

[sewwhat89]

I am shooting two 300 SAUMs and a 7 SAUM, and in both cases, the RP 9.5M primer is the best hands down. I bought some Wolf LRM primers to see if they may be more consistent; however, they must be a much hotter primer. I was getting excess pressure from loads 1-2 grains below max loads with RP9.5M primers. The one load in my 7 SAUM that did not have a noticable excessive pressure change showed a slight decrease in velocity and ES/SD, but the groups were slightly larger than the RP9.5M groups. I am going to try the load again at 300 yards to see if there is any discernable difference and to double check the chrono numbers under different lighting conditions.

I would say the RP9.5M is THE primer for the SAUM case. CCI BR2 is a close second.