Just FYI:

The 1937 DWM catalog that I have lists one load for the 8x60 Magnum Bombe cartridge: 12.0 gram bullet at 891 meters per second which equates to a 185 gr bullet at 2923 fps.

For comparison with the same bullet weight, the catalog lists two regular 8x60 loads as:

12.0 gram bullet at 791 meters per second which equates to a 185 gr bullet at 2595 fps.

12.0 gram bullet at 817 meters per second which equates to a 185 gr bullet at 2680 fps.

Barrel length for all is listed as 65 cm (650 mm = 25.6 inches)

meters x 3.28084 = feet
grams x 15.43237 = grains

Cheers!
-Bob F.