Alexander Arms will have a new cartridge out for the AR15 later this year. It is being branded the .26 Grendel.
The .26 Grendel is a 6.5mm round for bullets up to 130 grains. With a 123 grain Lapua Scenar, the round will do 2650 fps with a 24" barrel. In a 16" barrel, it will do 2500 fps. As reference, the 123 grain Lapua Scenar has a .547 BC at 2650 fps, is still supersonic at 1,000 yards.
The round is a factory / production version of the 6.5 PPC. I have been shooting it for 2+ years and it is very consistent and accurate. Recoil is mild.