Optimized Caliber

[stanc]

From a logistics standpoint it would be rather advantageous for one cartridge to cover it all. I'd be willing to take the hit on overall loadout quantity in exchange for increased lethality and penetration from short barrels at various ranges, not just up close.

Those arguments are also put forth for the 6.X GPC (and Murray's 7 UIAC). The main difference is in the size and weight of the weapons. The GPC/UIAC require guns as big and heavy as for 7.62 NATO, whereas Grendel fits the smaller, lighter firearms made for 5.56 NATO.

Both of the above would completely replace one NATO cartridge (5.56), and so may be a better fit to the Army way than Paul's 6.5 Super Grendel, which would require adding a third caliber to the inventory alongside 5.56 and 7.62 NATO. From a purely technical standpoint, the Super G seems very attractive, but IMO it has the least chance of success. Plus, as you noted, one cannot demonstrate something that does not exist.