I was musing over an idea for a fully assembled upper with a night vision scope that would fit on any customer's AR-15 lower. I wanted something with more ft. lbs of energy than a 55 Gr .223 that would still fit the AR-15 platform.
To help with the decision I graphed out some information on 5 very popular rounds, although two of them are AR-10 based they are included for comparison. In the graphs below the colors represent:
Red: .223 50 Gr GMX Full Boar
Grey: 6.5 Creedmoor 129 Gr American White Tail
Dark Blue: .308 165 Gr American White Tail
Light Blue: 6.5 Grendel 123 Gr Custom
Gold: .300 Blackout 135 Gr
In general the two 6.5's and the .308 all stay fairly close to each other in velocity.
In the trajectory arena all of the rounds except the .300 blackout are so close that there is no clear winner....only a clear loser, the .300.
It is the ft. lbs of energy that each round distinguishes itself. The .308 to no surprise has, and retains, the most energy. The 6.5 Creedmoor and the 6.5 Grendel start off in evenly spaced gaps down from the energy of the .308 (2,300 and 1,800 ft. lbs. respectively) but they start to converge at 500 yards. The .223 and .300 blackout both start much lower in energy and wind up lower at 500 yards but at about the same ration of loss as the others.
After looking at the data we will soon be offering a completely assembled 6.5 Grendel upper with bipod and night vision scope. Keep checking back for the final spec's and cost.