I'd like to think that some of the discussions reproduced on this page had some part to play in this. JD Jones of SSK Industries now markets the 6.5mm MPC round based on a. The 6.8mm SPC requires new magazines and is not compatible with current belt feed mechanisms. That means economic and logistical benefits as well as improved performance. 223 case will not equal the 6.8mm SPC on paper but will still out perform any assault rifle round in current use, and the only modification needed is a new barrel and possibly a new gas port and tube. Stan beat me to the punch on that one so this is known as the 6.5mm SCC rather than the 6.5mm ARC! 223 case was also of interest (and was to become my preference). I'd christened this proposed round the 6.86mm ARC and this round was featured in Special Weapons for Military & Police no.27 (many thanks to Stan Crist for the mock-ups of the rounds).
![thermold subsonic 223 thermold subsonic 223](https://i.imgur.com/mPYLDix.jpg)
My initial thoughts were that a 115gr 6.8mm round appeared to be a good starting point for a case of this powder capacity. Acceptable exterior ballistics can be taken to mean any performance better than the 7.62x39mm. This implies the largest bullet from which we can get acceptable exterior ballistics. Terminal ballistics at combat ranges is the area in need of improvement, not extreme range performance.
![thermold subsonic 223 thermold subsonic 223](https://beckammunition.com/image/cache/data/ammo/rex/308_180gr_rex-550x560_0.jpg)
222 Rem/.223 Rem/.221 Fireball case so it can be used in unmodified magazines and belt feed systems. Summary: Any new round adopted must not just be for a new model of rifle, but easily compatible with the vast number of 5.56mm weapons already in service.