I need someone smarter than me to help me out please. I bought 50 pieces of once fired 308 norma magnum brass for dirt cheap and I figure I can use it in my 7mm rem mag. I ran it through my full length die and now I need to figure out what to trim it to so it ends up good to go after fire forming. Any ideas? Thanks

Trim it to the trim length for 7rm.

But why???
You could have sold 50 once fired 308 Norma's for enough money to buy 100 new 7mm Remington magnum cases.
Too late now I guess..

2.5" for 270 wby brass resized to 7mm rm as well Or will the double radius end up making it longer?