Gotta say, looking forward to the pack & ballistics. Spartan0536, have you considered looking at 6.5 PCC ballistics? The cartridge is designed to work better out of a shorter barrel than the Grendel (meant to use faster powders, generating more energy in a shorter barrel), and uses the 5.56 as a parent case. Thus, you have loads comparable to the 6.8 (rule of thumb seems to be subtract 2 inches of barrel length from comparable 6.8), with full STANAG magazine capacity.