"The 6.8 mm Remington SPC (or 6.8x43mm) is a new rifle cartridge that was developed with collaboration from individual members of US SOCOM.[2] Based upon the .30 Remington cartridge [3], it is midway between the 5.56x45mm NATO and 7.62x39mm in bore diameter and velocity with more energy than both. It is particularly adaptable to current 5.56 mm NATO firearms, the cartridge overall length being comparable."
The military dropped the idea. I see little use for the cartridge except for those who think deer hunting with an AR-15 style rifle is good for our public image.