Test barrel length: 24 in (609.6 mm) Source: Remington 
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. Based upon the .30 Remingtoncartridge, 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 the same.
Though ballistics similar to the 1950's era .280 British, improved powders allow the 6.8 mm to have a smaller case. The 6.8 mm SPC (Special Purpose Cartridge) has a muzzle velocity in the 2,400 feet per second (730 m/s) range from a 16 inch (406 mm) barrel using a 115-grain bullet.
The 6.8 mm Remington SPC is designed to deliver 44% greater energy than the 5.56 mm NATO at 100-200 meters. When compared to the more powerful and well-established 7.62 mm NATO cartridge, the 6.8 mm falls short in all these areas, but has less recoil and is more controllable. While the 6.8 mm generates around 1,759 ft·lbf (2385 J) of muzzle energy with its 115 grain bullet (note: this figure is from an unrealistic 24" bolt-action test barrel), the 7.62 mm NATO (M80) fires a 147 grain bullet at 2,750 ft/s for 2460 ft·lbf of energy (838.2 m/s for 3335 J).
While the round is generally intended for use at shorter ranges, this handicap somewhat dampened the initial enthusiasm over the SPC round, and given competitors like the 6.5 Grendel or improved 5.56 mm rounds an opportunity to compete for acceptance. Many criticisms fall short considering the majority of military engagements (even with modern optics) occur inside 300 m (U.S. Army Continental Army Command Operations Research Office ALCLAD study, and Gen. S.L.A Marshall, cited on p. 15, "The Complete AR-15/M-16 Sourcebook", Duncan Long, Paladin Press 1992, 2007)Cite error: Closing </ref> missing for <ref> tag..