There are various theories on loading for the old NE cartridges that were originally designed for Cordite. I have been loading the .450/400 3" for 20 years. My rifle was regulated for the 55 grain "Tropical Load", which was less than the 60 grain standard. Reason for this is that Cordite was a bit temperature sensitive.
I was told that you could use IRM 3031 in 1:1 substitute for Cordite, and have found that to be true. My load is 56 grains of IMR 3031 under Woodleigh 400 and Fed 215 primers. That load runs about 2025 fps and has killed elephant, and a number of Cape Buffalo without incident. 400 grain solid penetrated a 300 lb wild boar lengthwise. That's 4 feet of hog.
The .450/400 case capacity is not as large as some other NE cartridges. I also load for the .450 #2 NE. In that case I use 105 grains of H4831 and 2 grains of polyfiber. The poly is used to keep the powder from sloshing around in the large case. I don't use poly anymore in the .450/400, but you could. If you use poly, weigh it every time!
IMR 4831 and H4831 are popular powders for loading NE cartridges, as is R15 in some circles. I've experimented with those in the .450/400, but none were better than IMR 3031 loads.
R15 - 61 grains worked well
IMR 4831 - 75 grains
H4831 - 79 grains
Guns vary, so work up to those and use a chronograph and DO NOT TRY TO HOT ROD NE loads. 2050 fps is the range that seems to give the best performance, and 2100 fps in a double is tops.
Find the load that regualtes the best that runs between 2000 and 2100 fps, and you are good. Once you find that combo, your experimenting is over. Write it down and go with it.
Best of luck!
Hatari
