Originally Posted By: italiansxs
I intend to do the following unless someone has a better idea:

1.Obtain some 303 British Enfield brass
2.Fire form the cases so they're the correct size albiet a little short.
3.Load the cases full with blackpowder.
4.Crimp the heaviest 10mm bullet I can find in and start from there.

Thanks for the info PWM but I expect there's a safe smokeless equivelent to the black powder load. It's just going to take a little digging.


yes, that will be the way to go.
Some more things to consider, from my own limited experience with loading old cartridges:
- different brands and granulations of black powder will give different results
- if using less than a full case of blackpowder, use felt or cardboard wads to fill up the case
- finding the right bullet may be trial and error. Finding bullets of the correct diameter may be difficult. Smaller diameter bullets can be paper-patched and adapted.
- use a chronograph, not only for velocity readings but to check consistency of your loads

Of course in a second step smokeless can be tried. Data for "original" loads are either not to be found or they are useless anyway, because the old powders are not available any more. One has to establish new loads.
There are plenty of options, I am only pointing to a few (no details, because working these out is up to you):

- a reduced load of IMR4198 or H4198, 40% of the established BP weight, plus a filler, either Dacron wadding or some "foam rod" - note that there is plenty of discussion what is correct or not
- use of very bulky powders, omitting the filler - I like SR4759.
- "Trail Boss" may be another option

Again the chronograph is essential, stay with the blackpowder velocities.
You can compare available loading data for similar cartridges, in your case mabe .40-62 or .40-70
And there are other boards that are focussed on reloading, you might try here
or here