Good choice. 6.8 is just a specialized .270 cartridge.
"The 6.8 Remington SPC is based on a .30 Remington cartridge case, but fires, you guessed it, a 7.035 mm projectile. If you don’t recognize 7.035 caliber, that’s just the metric measurement of the popular .270 which is actually .277 inches diameter. See, there's that goofy tendency to name cartridges something different from their actual diameter again. Just like a .38 Special being .357 caliber.
In simple terms, think of the 6.8 Remington SPC as a .270 Winchester with a smaller cartridge case and less powder capacity that can be fired in an AR type rifle with correct barrel and bolt."
But they are coming out with a .224 Valkyrie cartridge now that is supposed to have amazing ballistics out to 1200 yards and less recoil than 6.5 Grendel.