Yep. I agree with his post. Additionally, you want to load the bullet to not sit on the rifling. I test this at least 6 times till I get a really good indication on the OAL the leade will take and then shorten the OAL so the bullet is not sitting against the rifling when chambered. Also, if it's a box fed rifle, your mag length is probably going to be your OAL limiting factor. Make sure to measure that too and see what length round it will take.

Tomorrow after class, I'll check the specs I use to load the Rem 700 I have in .270 and post it. I haven't loaded for a Barnes yet, but it will get you some ball park numbers.