My Brother and I are doing the same thing with the std 7 Mag with .210 freebore.
Two loads, 26", 9T, #5 contours, Brux and Krieger 4G, a third in an X Caliber barrel-6G
A. R#22 shoots a single bullet hole with R#22 at 2860
B. R#26 shoots sub 3/8" with Fed 215's, 3030 fps
Remington Brass, non-trued 700s, Boyd's stocks, Gentry muzzle breaks, Burris signature 6x24 with the light seeker front objectiveDies are Forster bullet seater and FL sizer, while I found the best accuracy with a '79 RCBS full-length sizer....go figure. We full-length size every firing. Beater rifles are not supposed to shoot this well, but they do.
I don't think a guy could go wrong with a 7 PRC or 7 Rem mag as they have almost identical case capacity.
The 7 Rem mag will feed flawlessly in the Mark 5, I don't know about the PRC.
28 Nosler is equal to the 7 STW in case capacity, or darn close to it. 28 Nosler cases(AGD), anyone making 7 STW Brass?