For use in the AR15 and using mil spec extensions, the bolts are stronger without a doubt. The 6.8 mags are wide enough that they do not pinch the 6.8/30 Rem case. There are several cats based on the 6.8 case. 5.56x42,6x41,SIX5, 6.8, 30 Herrett and a 358 when it is finished.
The shorter case of the 7.62x39/6.5G allows the use of longer bullets if the other obstacles can be improved upon. I don't think the issues are big enough to prevent it from being used as a hunting or target round but I don't think it is reliable enough for combat or duty use.
I designed and manufacture a bolt that is plenty strong enough but it requires a different extension. If some company were to machine a lower with a wider mag well like the LWRC SIX8 but designed for the 220 R/PPC case and then made mags specifically for that lower and case it would greatly benefit cartridges based on the 220R/PPC. IMO that should have been done on day 1 but, it takes money.
