These now have M4 feedramps (check before ordering to make sure you are getting a newer upper).PRI mags work well and they also sell an adapter to convert the threads for different muzzle breaks/flash hiders. Ammo is more expensive but is more versatile and harder hitting. Check out the 6.8 forum for more details on the 6.8, mags, uppers, etc.
Was this review helpful to you?
7 of 8 people found the following review helpful:
Good Shooter
February 14, 2009
Reviewer:
Mark Hyder
from Vail, AZ United States
I have a left hand 5L model. Shoots good. No problems feeding from PRI mags. I've used SSA and Rem ammo so far. I will try Hornady if I can ever find any. More recoil than 5.56 but much less than a .308. If you are looking to upgun your AR lower this is the one to get.
Best 6.8 upper for the buck! 
Good Shooter 