I'm right about to put in an order for a Pac-nor barrel, 20" chambered in 7mm BR. I'll be slinging medium to heavy grain bullets (140-160gr) so the twist will most likely be 1 in 9. My question is, how many grooves should I go with. The only other custom I had built was a 6.5-284, and got a 3 groove (not really my decision). Given my twist requirements, I could go with pretty much anything, including a 3, 5, or 6 groove barrel. I'm leaning toward the 3 groove (don't know why), but any input is welcome.