Yes I know I'm a noobie here,but has anyone in this thread mentioned the
6.5 Grendel?
I know that ammo is a bit scarce for it right now but the round was designed as a compromise between the 5.56 and the 7.62x51. It's still light, so you can carry a decent amount of ammo, but it has a lot more carry and punch at extended ranges.
Just throwing a thought out.