Come on, now folks are starting with the bolt actions. The greatest battle rifle ever is a bolt action? I respectfully disagree with you guys and your nostalgic ways. Our troops are delighted that you don't run the armory though.
I say greatest in respect to its time, sir.
If I were to arm our soldiers RIGHT now, it'd be with the ACR.
If I were to arm our soldiers in four years, it'd be with a caseless rifle.
The ACR is the best rifle in general that I can think of for modern combat, especially when in 6.5 Grendel.
And it does qualify as an MBR (because assault rifle is a subset of MBR), so, yeah.
Heck, if you want to go with bang for the buck, than the AK-47 is your man.
The AK is THE ONLY rifle for many people.
The AR... just doesn't have that distinction.
In many foreign countrys, when they say "rifle" they mean "AK". They have become synonymous.
60 years ago, the Enfield held that spot.