empirevr:
If you look on page 77 of Wrighty's 2nd edition, you will find a table of recommended 'factory load' equivalents for Nitro-for-Black cartridges.

The .500/.450 shows a 350gr bullet at 1950 fps.

The .450 x 3 1/4 shows a 350gr bullet at 1970 fps and a 365gr bullet at 1950 fps. A few reduced loads which still regulate are given there as well.

Like Tinker, I get just over 1950 fps with a 350gr Woodleigh from my Tolley .500/.450 x 3 1/2 if I cock my hat at just the right angle. That's with 72gr AR2208 (=Varget). The ME is around 3000 ftlbs.

According to Graeme Wright (on the same page of his book) the .500 3-inch turns up 1850 fps with the 440gr bullet. This matches the Kynoch factory-load of 100+ yrs ago, and gives ~3350 fpe.