If you're talking prc brass I think you are confusing the sherman max and the Sherman magnum.I haven't been able to load for it I'm still working on getting my PRC brass shot so I can reload
I am running a 21.5" barrel on my 300 max but never tried 4350 (of any flavor) or anything lighter than 208 grain. Love my 300 max. Shooting the 208 eld m at 2893 fps with rl 26. I also load for a friend with 300 max and use 208 eld m with hybrid 100v with 22" barrel at 2815 fps.