Bonanza:

US suppliers have new Kynoch in .350 No. 2, but no .400/.350. These are different loadings of the same cartridge and if your gun was regulated for 310 grain, the No. 2 won't regulate well with it

Roosevelt and Drake has original Kynoch .400/.350 listed, but I don't know how old it is. Old cordite is usually OK, but not old NC. For an evaluation shoot, since this is original ammo, I'd probably try it. They have both Kynoch and Eley Bros. listed. Get the Kynoch. Never shoot the old Eley stuff. If you try it, check the primers. If the cups are copper, they're corrosive and you'll need to flush the bores with hot water after shooting. Brass cups are non-corrosive.

For brass, I've used the Bertram .400/.350 and it was only good for two rounds. Get in touch with David Little at Kynoch, their stuff seems to be available in component form now. Horneber will also make it. Easiest to just form it from RWS 9.3X74R. This case is virtually identical to the 9.3 except for length. Woodleigh makes the correct 310 grain bullets.

Standard data for this cartridge was sometimes reported incorrectly. 43 Cordite and a 310 grain bullet for 2000 fps, not 2150.
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