Hi Dave,
I guess I got the idea about cutting off 375 Winchester reloading dies(RCBS) for use with the 375 Supermag by looking at the maximum case length of the two cases, ie 2.020" and 1.610"(only reference I have access to) respectively which shows a 0.410" difference. So I thought about cutting off some 375 Winchester brass and some RCBS 375 Winchester reloading dies and see if the result could be used with a 375 supermag revolver.
In looking at the body taper/inch rate numbers on both cases with the shortened 375 Winchester case(cut down to 1.610 to begin with); it appears that the slightly larger diameter numbers of the 375 Winchester parent case at the base and at the shortened area will get close to the supermag dimensions when run thru the shortened die. The brass thickness at the shortened 375 Winchester case is something I have no information about yet, but guess one could always ream if necessary, I just do not know how the thickness will really turn out yet.
I believe that 38-55, 30-30, and 32 special(as others commented on) could be candidates for parent brass(due respect to pressures) to be run thru the shortened dies if the 375 Winchester is scarce etc. By shortening the 375 Winchester dies by approximately 0.410", the taper of the die will constrict based on the linear? taper of said die, and hopefully retain the roll crimp if the die has it. Probably need to research(just casual so far by me) the dimensional numbers on the two cases/die set some more to get more confidence in the approach, but so far looks kinda feasible and these 375 Winchester dies/brass are expendable in my situation here.
So just trying to use what I have to get a pistol shooting. I have shot a 10" 445 and a 8" 357max, but not a 375.My 375 supermag pistol is a 8" model, which I suspect is the common variation during those years.
regards,
Rick W.