I also agree that the MBR is a antiquated concept, mostly for gun nuts who like big booms and think the AK and AR wont get the job done.
Much that you don't understand, dom. Of course the AR calibers will get the job done. There are too many bodies in the ground to deny that...but there are other targets besides human in a battlefield situation. The other side's war materiel can be damaged or destroyed with the extra punch afforded by the full power cartridge...not to mention the extra range with residual killing power. Like the speed afforded by a Corvette. Not often needed...but nice to have in case it is.
Do I personally as a civilian have any use for an MBR? nope.
Allow me to point to the Winchester 70/Remington 700/Ruger 77 "sporting" rifles chambered for military cartridges in civilian guise. (.30-06 Springfield and .308 Winchester) that have been used to take all manner of large game...often at distances that would fairly boggle the mind.
It was always my impression that militaries all over the world abandoned full power semi-auto weapons when they realized a normal soldier cant make 800 yard shots.
The change came about largely due to the fact that personal combat didn't normally take place at distances greater than 300 yards...and most often at 100 or less. Additionally, it was found that a good many infantrymen wouldn't take deliberate aim at an enemy soldier until that enemy was almost on top of him...leaving little time to aim. In that scenario, a high rate of fire was/is more important than precise shooting.
In WW1, the infantry still used mass area fire at extremely long distances...aka "Plunging Fire" in the attempt to break up enemy concentrations or hopefully be able to reach him in the far trenches. The original .30-06 cartridge...designated Caliber .30 Ball M1...was loaded with a heavier 175 grain bullet that was conducive to effectiveness at extreme range. The switch to M2 Ball with its 152-grain bullet was easier on Garand op rods and produced less recoil...and was better suited to the mobile battlefield of WW2. Still a reliable killer out to 500 yards, but even that was no longer necessary due to more accurate artillery, air support, and armor...long-range area fire by riflemen became an obsolete tactic.
In the hands of a civilian, operating alone...a rifle chambered for the MBR class cartridge may be of more use than one might suspect. Distance is your friend. More than that...the full-powered cartridge can stop a man...or a truck dead in its tracks with a well-placed shot at pretty extreme ranges. For those reasons alone, I opted for the 03-A3 Springfield. "It encourages aimed fire...thus conserving ammunition...and it discourages becoming involved in a firefight...thus conserving life and limb."
As a final point...The term "Gun Nuts" is used all too frequently by those who would take all our firearms away and leave us in the role of the king's subjects. This notion of "need" as a requirement or a justification for ownership should be stricken from all discussions. Need has nothing to do with it.
If I want it...my reasons are mine alone, and that is justification enough for my having it.
Remember the fallout generated by Jim Zumbo's statement concerning "Assault Rifles. That works in both directions. I have no personal need for an AR15 or an AK47...but if somebody else wants one...I'm behind that 100% and would never make disparaging or derogatory remarks as to that choice.