Gunny,
IF you are seriously interested, try this.....if not and your filthy rich like Old Savage, just keep buying jacketed bullets.
Get 20 cases....get dremel tool......get sanding drum of appropriate size.......get micrometers and measure wall thickness.......sand out .001 on one case (inside) for the depth of the bullet when loaded.......load it with a .412 bullet...no primer or powder......test.....
If it works do 20 and load with the same load.....no need to change powders.......keep variables to minimum......
I'm sure you know this but a cast works best at .001 over groove diameter.....002 is better with light to mid range loads.
On handguns size to throat diameter.....if throat diameter is smaller than groove diameter, the throats need to be reamed.....I've done them with Dremels ......with an exacting "grinding tool", then a polish....."polish" NOT Polish.
Forster will make you an inside neck reamer for whatever diameter you want....they have done some for me to the half thousandths for some antique Winchesters.