1680 & 680 (if you can find it) are great powders for the .256. Foolish I sold a 21" Contender barrel along with forming dies. I still have a 10" Contender barrel along with several hundred factory loads. A fun Cartridge to play with, & will really roll up a Groundhog.
I have mostly 256 brass, but I have over 50 formed from 357. A couple of days ago I thought I'd try forming from 357 again. I had not done that since the 70's.
I have heard that 30 Mauser dies work well for the first pass in forming, then use full length 256 dies. I don't have 30 Mauser dies.
What worked for me was to run the 357 brass into the full length 256 dies until the shoulder was starting to form, then I ran the case into a 32 S&W long die enough to look like a 30-256 cartridge. Then I ran the case into the 256 die again.
