Because it fits in the AR15, lighter, more rounds in the mag. You need an AR10 for the Creedmoor.
Is the civilian AR market for a cartridge like this larger than that of the bolt gun shooters?
No information to back this up, but EVERY gun store I walk into is LOADED with ARs and accessories. Bolt guns are there but the crowds are around the AR's mostly.. AR's seem to fly off the shelves.
