I'm not going to go into great detail as I still have a few depositions on this coming up, but there is a trade-off on everything, and with the .mil, consistency is king, and that caters to the lowest common denominator.
It is VERY unlikely the the .277 Fury will make into the hands of the average Joe. SF types first, DMRs certainly, Light machine guns, sure. Common Infantry, nope. Son is in the Honor Guard and was working funerals last week. His partner forgot his overcoat, so, in deference to consistency, neither could wear their overcoats in the snow. It is the way it is. The M4 is light, simple and shootable by 90 pounders to 220 pounders with the flick of the stock.
I have several friends who have been allowed to shoot the Fury's, I have a few cases on my desk. These are highly skilled marksmen, and they report stout recoil, charging, etc. One felt it was more difficult to charge and shoot than his .308 gas gun.
An experts gun is not always suitable for the common person. The .223 AR15 is an equalizer in that the relatively frail can shoot it reasonably well, and longer, than almost anything else available. I can shoot my 5, 6 and 7 pound ARs faster (with the same accuracy) than anything else I own. I can beat my 9mm carbines and pistols with a .223 on almost any drill you toss at me. That is going to be the same for any skilled to proficient to novice shooter.