I am looking into the purchase of a new upper and I need advise in the best caliber for a AR-15 platform. I would like to have the best BC bullet into my excisting lower. Any advise would be welcome
6.8 is a great caliber not much more expensive than 556 when reloading otherwise around $20 a box seems the norm. check out arperformance.com. also you can use your existing lower and even 556 mags but definately not recommended. hope this helps.
6mm and 6.5mm bullets have pretty comparable BCs, but the 6mm can be slung faster. Both have better BCs than the stuff in 6.8mm. If you're target shooting past 500 yards, 6.5 Grendel and some of the 6mm wildcats are worth a look.
If you wanna whack deer or hogs under 300 yards with an SBR, 6.8 is the man.