Actually here in Italy there aren't many slow powders available.I think that those intended for the 50 BMG could work well,but they aren't imported here.The must common slow burning powders available are the norma mrp and the N540.

OAL is not a problem,actually the sample pictured above is only a dummy for display purposes.
I think that a lenght of about 3 inches would be right for this cartridge,a lenght that allows it to be chambered in a 6,5 x 55 mauser lenght action.

Case capacity is,according my measurements,a bit greater than the 240 weatherby,so the body lenght could be shortened of about 3-4 mm

The idea behind this cartridge was to offer a 6 mm that could use heavy bullets launched at high velocities with a short-and-fat case shape