I shoot a 6.8 x43mm and have bee studying up on the 6.5 Grendel as well as shooting a couple that I borrowed.
So far, my thoughts are that the advertised performance of both rounds has been greatly enhanced via a key board.
The whole idea of the 6.8x43mm was to make the cartridge conversion as inexpensive as possible. So the rifle had to end up as an M4 size rifle (carbine to us real rifle shooters) and that all the magazines and web gear had to stay the same size. Plus the round needed to work in the belt fed M-249 SAW system. The use of the old 30 remington case for the base of the 6.8mm works for that purpose. The whole caliber deal sounds like a classic govt' program compromise. The 6.5 bullets were better for range , plus accuracy, while the 7mm bullets had better destructive power against tissue. So they split the difference with the 270 caliber (6.8mm)
Basically I see the 6.8 as something of a souped up 30 carbine round.
I am firing 110 grain Nosler and Barnes boat-tails at 2,550 fps from a 16 inch M4 style barrel. This is in cold weather, such as what one finds in the mountains of Afganistan.
Even though I am using the best bullets (BC of .370) for that weight and length , being limited by the AR-magazine size and standaard AR action size, these projectiles slow down fairly fast.
Muzzle= 2550 fps
100=== 2315 fps
150=== 2203 fps
200=== 2093 fps 5 inches low with 100 yard zero
250=== 1987 fps 10.5 inches low with 100 yard zero
300=== 1884 fps 18.0 inches low with 100 yard zero
So at 250 yards, it is basically like shooting someone with an M-1 carbine at the muzzle range. With a pointed bullet instead of a round nose.
I tend to see the 6.8mm as a 250 meter, (maybe 300) cartridge. Particularly when fired from an M4 sized carbine, while using military grade ammunition which will not be as effective (or accurate) as my ammunition.
