Skimming, it sounded like the m14 vs m16 argument from ancient times. Where will battles be fought and what is the expected range? And if the grunts have to humo all their ammo, weight will be a concern.

Level 3+ body armor is getting way cheaper ever since China started manufacturing it like crazy and selling it to literally anyone. Unless the army wants to switch to tungsten or depleted uranium small arms ammo, they are going to need something like the 6.8mm. I'm almost certain that any problems they have now with the XM7 will get ironed out pretty quick.

I don't see them getting around the ammo weight issue though. I think that drone intelligence and better optics have made that slightly less of an issue. The only thing better than suppressing fire is accurate fire after all.