I have a rifle that's not a wild cat but it might as well be because I cannot find any loading data for it. So how do I come up with loading data? It's chambered for the 400-360 2-3/4 Nitro Purdey version. Everything you can find in print about this cartridge is wrong! probably because there are five different 400-360 cartridges, all non-interchangable. Books list rim thickness from one, base diameter from another, etc. all as one cartridge. So any way, I have things more or less sorted out as far as diminsions go. At present I am using 9.3 x 74R brass with the rim shaved, the neck trimmed back, and run through the sizing die. Bertram has allegedly started making brass for this cartrdige so eventually I will send off for some.
This cartridge was originally loaded with a round nosed 300 grain bullet of 0.367 inch diameter. the nearest I have come up with is a 285 grain 9.3 mm bullet that is 0.366 inch in diameter. The 300 grain bullet was pushed by 40 grains of cordite to 1950 fps according to published data from Kynoch et al.
So where do I start for a powder charge? This is a double rifle so changes in bullet weight, powder charge, velocity, etc. can throw it off.
I think it calls for a relatively slow powder that will burn smoothly at fairly low pressure. It's a big case. For a given pressure and velocity slower powder means more powder which may tend to offset the light bullet as far as regulation is concerned.
