The way I read the OP, sounds like he wants to neck a 7 mag down to 6.5. Interesting.
You should get more velocity than a 6.5 SAUM, but burning a fair bit more powder would probably give you less barrel life. That being said, 7mag brass can be found everywhere. Unlike the SAUM, PRC, RPM etc.
For twist rate, I'd think 1:8 like the PRC.
Like a .264 Win mag?




















































