[Sparta]

The 6mm PPC would be an equally good choice, too, but I doubt that it's Soviet-designed case would endear it to the military brass in the U.S.

Can you provide ballistics data on the round. If it's a good round, it wouldn't surprise me if the brass refuse a good weapon just because it's Russian designed. (The Su-35 and newest MiG-29 varients are superior to current US warplanes.)

[SBprone]

The hot ticket in across-the-course highpower competition is a cartridge championed by David Tubb that he calls the 6mmX. It will do things at the 600yd line that the 6mm-.223 wildcat just can't approach. The 6mm-.223 wildcat has been tried by many in highpower but never with much success.

I don't know if this cartridge is feasible in a modern rifleman's weapon but you can read about it at http://www.zediker.com/tubb/images/dies/xcdieins1.html

Both the 6mmX and the 6mm PPC have much fatter cases than the .223 and that may be the deal killer from a weapon design standpoint.