This has been an interesting read. I am flummoxed as to what this cartridge will do that a 35 Whelen IMP will not?
(If the bbl is set up for heavy CBs.
I believe the 35W as the 400W has been misserved by having a non G&H chamber as the SAMMI standard. The G&H chamber (as researched by Mike Petrov) is less tapered and has a distinct shoulder. The 35 would have done better w/the same shape. The 35W IMP does the same albeit a bit different shoulder.
Picked up a nice FI FN that's going to become a 35W or 9.3x62. Choices ---- always choices !