I have a CMMG with a 18 inch nitrided barrel that is very accurate. .3-.4 MOA with FGGM and Barnes Vor-Tx and a Bushmaster with a 6 inch chrome lined barrel. We have had at least 2 carbine coure students shoot part of the course with LR-308's and one Rifle Instructor Candidate shoot a JP Enterprises .308. That JP is a sweet rifle! The biggest ossue with them is weight. The Bushy ORC is the lightest at 7.75 pounds dry. With an Aimpoint Micro, a sling, and a 20 round mag it's about 9.25 pounds, which is heavy but manageable.
You will never begin in the fight you have planned for. You will begin in the fight the other guy has planned for. Retreat in a manner that leads him into your fight should he press his attack.