Nitrox, the 6.8SPC is a Remington 30 shortened to fit in the AR magazines and necked down to 270. Bit like a shortened necked down rimless 30-30. The 30Rem is a rimless case, not rimed like the 30-30.

The bolt face is larger than a 223 but smaller than a 308. The Ar magazine that holds 30 5.56 will hold 28 6.8SPC and 26 6.5 Grendel. The 6.8 can use the same follower as the 5.56 but the Grendel can't. It was developed by a group of US SF blokes who wanted some thing that would reach further, hit harder, put a bigger hole in people than a 5.56. It also had to work through a M16 platform.

It is a great little round, way better than any 223. I have taken numerous pigs and goats with it. I would feel comfortable taking Red Deer out to 200 with it when using a 115 or 120 grain projectile.

I know some have necked the case down to 6mm and was wondering is anybody would neck it down to 224.