.280 Enfield...Ahead of its time

[adamjp]

Yeah, that's pretty obvious. Like I said, I think ambidexterity was not the real reason the US turned down the EM-2.
Likewise, I think 6.5 SPC (w/long, high-BC bullets) would be a better choice than 6.5 Grendel for your MRMG. I know it's heresy to say that here, but the extra 4mm of case length would eliminate some problems inherent to the short, fat Grendel case.

I think you are onto something there. I've been toying with the SPC cartridge, but in different calibres. The 6mm SPC (pretty much aka the 6mm WOA) looks quite nice as a little hunting round.

IMHO the 277 bore and the reasons put forward for it's choice make sense - for SF types. Since they represent a tiny proportion of the Army perhaps a wider viwe should be taken and that means a 6.5mm bore is more logical.

TO be honest it is all academic, the way to do this properly is to decide the effect you want to deliver, and then design the bullet to do that, and a cartridge to propel it. Things like the Grendel and the SPC are still tied to the available parent cases - a company with resonable resources could start with a greenfield design. I think this is what is suggested in the Optimised Calibre discussion (I've been away and have not had the chance to read it yet).