Thanks for the response, Judson. First, let me say how very cool it is that you can earn a living wildcatting. You are a lucky man.
If you check the specs for the Canadian mags, I think you'll see they're based on the Jeffery.
The perfromance of your 9.3 is quite impressive indeed. Should handle anything you put in front of it. There's also a 358 RG, a 378 Weatherby necked down, and with the same venturi shoulder. Pretty hot stuff.
Back when I wrote the first post, I was looking for a big elk-buster that could also handle bruin if it came to that. I chose the Jeffery case, for a number of reasons, most of which boil down to efficiency vs performance. I can get most of the speeds of a Rigby case with much less recoil, and at any rate way more than I need. I have 280g North Forks ushering forth at around 2950 (but I don't push it that hard, more like right at 2900) and 250's go to 3100, maybe beyond, though I haven't tried. This is a 26" bbl, also. The Weatherby case gave the 358 RG another 100-150 fps, so the gain is there, but he's also using about 28% more powder to get 5% more speed. Not my idea of a good trade. There's some monster 308 and 338's made on improved Lapua cases, and it would seem a natural fit to try that case necked to 375 and trimmed to a 3.6" COL, loaded with 350g solids at maybe 2600 for the bigunz. Add a 270g of your choice, and forget the second gun. Sort of a 378 K-T beltless.
And I agree with Crispin to a point. I think the smaller calibers do have use for the bigger cases, but they need the longest bbl you're comfy with (26-7"?) and the heaviest reasonable bullet (.30 SD) for it to make any sense at all. Basically like the big brother of a 6.5-06 shooting 160g.
Have you had a chance to hunt with your creation? I'd love to hear stories.
Happy shooting!
Taylor