Isopeura,
Yes I kind of realised that, opening the 375H&H was just to give an indication of what it looks like. The 404/375 that I'm fiddling with ends up as a straight tapered case with a parallel neck that A-Square called a 'ghost shoulder'. I think comparison to the 450/400 is justified as that's what these cartridges look like, long, slim and sleek! That's why I mentioned a 450gr at 2150fps ... if the 423" wildcat will do that, it's like a 'modern faster' 450/400.

Have you got the CIP specs for the 400H&H? I haven't checked them, but the pressures it's designed to operate at would be of interest.
Cheers...
Con