The 8mmRem Mag is a grest chambering. It has mostly been pushed aside by some of the RUM,SAUM,and WSM loadings as of late.
I had several sports shoot it for moose in Maine,always with good outcomes. But it is one of the "gotta pay to play" chamberings. I still shoot a handfull of them including the 416Rigby,7STW,375JDJ,and others.
Take a look at some of the brass suppliers. It is out there. Possibly even Remington.
Good Shootin'. --- SAWMAN