10mm to 40 S&W Shotshell

[crandall crank]

I'm about to load some 40 cal shotshells. I will start with 10mm cases and use a die to put the shoulder on the case. Has anyone else done this? I am mostly concerned about the amount of powder needed. I typically use either Unique or 231 in pistol shotshells.

The actual loading will not be a problem since I have made shotshells for 45acp, 45LC, 357, 410 (from 303 Brit).

Hoping to get a little guidance and not reinvent the wheel.

[SWANEEDB]

I have loaded up a good deal of the 10mm and 40's, using 10mm magnum brass, around 4/500 total before health went down, enough where all my reloading and casting is now no longer. The 10mm mag brass is quite scarce almost impossible to find. Making the shotloads is really quite simple, looks like you have done quite a bit of it already, if you scale down further on these threads you'll see a bit of info on the 10/40 loads. I have some info written down, just need to locate. ?'s just ask.

[DDriller]

If you can't find 10mm Magnum brass .338 specter brass will work as it is just 10mm mag brass necked down

[crandall crank]

I've got enough 10mm brass to make quite a few.