You obviously know nothing about the AR-15:
It's way to destructive for hunting.
AR-15 style rifle - Wikipedia
It's no more destructive with the first mag than any other rifle. But the fact that the mag is so easy and quick to change out makes it more destructive when you fire 3 or 4 mags as quick as you can. And there is no hunting application where you need to be quick changing the mags out like that. Only in a fire fight is that necessary.
My Mistake. I was referring to the original specification for the Armalite AR-15, but that was based on a 5.56mm round.
And the 308 was as well. So was the 303 British and a host of others. But those all were built in a day when the same concept was also used in hunting rifles. The construction was the same as the hunting rifles that came before them. The AR was designed from the ground up to kill with nothing left for cosmetics. Every feature about it was designed for the combat field of operation. Not one ounce is designed for hunting. The fact that it can be used for limited hunting doesn't make it a sporting rifle and not a combat rifle. it's a combat rifle. A thoroughbred Combat Rifle.
To this day, you can swap all but about 2 or three parts between the Colt Model 750 (AR-15 Civilian), LE6920 (made for Law Enforcement), the Model AR-15 Model 601 (Made for the Air Force in 1962), All version of the M-16 (Models 602 through 604) and even the cheap knockoffs or clones. They are all chambered for either the 556 or the .223. The difference between the 556 and the 223 is about 300 fps at the muzzle. The 556 has a higher chamber pressure so not all knockoffs should fire the 556 if they were chambered for the 223. But there isn't enough difference between the two to really make any difference in a mass shooting. It's not the shell that makes the difference. It's the fact that the design has no function other than to kill. It's not pretty, no frills, no cosmetics, nothing. Every feature has a reason. It's light to carry for long periods of time. But the real thing it has going for it is it's simplicity in using. It takes about 20 minutes for almost anyone to almost master. It's also the fastest reloading of mags of them all. I can change out a spent mag in just over a second when I am in trim. That means, I can push a bullet out in less than a second, shooting 60 rounds out in 61 seconds accurately and then in another 61 seconds, put out another 60 rounds accurately out again using 4 mags. And that is with ANY of the better versions of the ARs including the AR-15 Civilian and the M-16A-4. Forget about the 3 shot burst. No one uses that stupid feature. You hit your aim point on the 1st round and you are off target on shots 2 and 3. Wasted 66 2/3 % of your ammo that way.
As for the old AR-15 Model 601 and the M-16A-1 and 2, Full auto was just a waste of ammo and looked good in the movies. It wasted a lot of ammo and probably didn't hit shit. It just made your enemy temporarily put his head down until you ran out of ammo which was pretty damned quick (about 10 second). And the 11th Commandment is, "It's a huge sin to run out of Ammo". In fact, it's a deadly sin.
In the end result, the AR-15 and it's various clones are just as deadly as the M-16A-4 because they are both used as single fire weapons. But the fact that both are capable of being operated so easy and reloaded so fast makes both sought after as combat weapons. And yes, the US does export AR-15s and Clones of Mil Specs and so does Belgium.
Before you go on, I suggest you get a little bit more educated. Talk to us Veterans that have used the weapons.