First, the 7 Practical is different than a standard 7/300. The Practical has it's shoulder angle increased and I think the case body is wider. It's a fire forming case, for sure.
A straight up 7mm/300 Win Mag is what I built. It's a simple necked down 300 WM case with no other modification. I'm running the 195's in an 8" twist at 2990 fps with Retumbo. I can get up to 3030 but with some pressure signs. It shoots great. If you run R33, you can get up around 3040 no problem. But I didn't want to use a double based powder. Good powders for the 195 would be in the Retumbo burn rate area- R33, IMR 8133 (new).
The reamer used on my chamber was the bore rider reamer from PTG. COAL is right at 3.680", to keep it under the 3.7" max magazine for me. I can seat it touching around 3.720" or so.
My barrel is a 1:8" twist. I have 3 barrels still available, if needed. A 1:8.25" is recommended minimum twist for the 195 or 197 bullets. A 1:9" will NOT work for the 195's (bullets were tumbling at 200 yards).
Dies, I am using Redding 300 WM dies with a 7mm neck bushing. It's easy.
We have built several of the 7/300's and like them a lot. I have not had much playing time with it recently. I've been to busy with customer rifles and hunting season lately.