Pretty much all of them, and they have been for decades.
What exactly is unethical about using one for hunting? You do understand an AR-15 is no different than any other hunting rifle, right? They fire the exact same bullets. Pretty much every caliber for every type of game. Ironically, most AR-15 rifles sold on the market are chambered in far less powerful calibers than common large game hunting cartridges.
The entire term 'assault rifle' is made up. Outside of the military, or people willing to spend tens of thousands of dollars to own one, they don't exist in wide public distribution. The term itself was made up by people afraid of guns purely to make them sound scary, legislators in the 80's trying to get them banned for no reason. An assault rifle is fully automatic, primarily for military use. Hunters aren't using assault rifles. The AR in AR-15 simply stands for ArmaLite. That company developed it, probably over 40 years before you were born, back in the 1950's.
The AR-15 is the most widely used hunting rifle today. And has been for years. And that's what it is, simply a sporting rifle. They 'look' like a military rifle, but function completely different. In fact they function exactly the same as any other hunting rifle, one round fired for each pull of the trigger.
Here's the real reason they are popular. They are modular. You can get one basic setup, then switch out barrels and accessories. You can put in a large bore barrel to go shoot Elk, then switch it out to go for rabbits. Put in a shotgun barrel even to use for quail, pheasant, or turkey hunting. Then when not hunting, it can be switched out again for a good home defense system. It's cheaper than having multiple firearms that way, and your scopes, hand grips, laser sights... can all be used throughout.
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Let me show you the first rifle my parents bought me as a 10 year old kid. The Marlin Model 60 (not this exact photo, just the same model). A simple little .22 long rifle. Known by anyone who knows rifles as a 'plinker.' Great for shooting squirrels, rabbits, and other small game. Also great for continually shooting at the same tree as target practice, until that tree gets too weak and falls on his fathers RV. But that's another story. By all means, a great gun for a kid to start out on.
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Now, this is a much feared AR style Smith & Wesson M&P. Scary enough to have people calling for it to be banned.
Yet they are the same gun. They fire the same bullet at the exact same rate of fire, as fast as you can pull the trigger, release, and pull again. To single out an AR style rifle as anything unique is just laughable.
Actually, I lied a bit. There is one major difference. My 'plinker' I had when I was 10 years old, held more bullets. This 'assault rifle' below has a 10 round magazine. My rifle held 18 bullets in the tube. I routinely carried around 1.8 times the killing power of the AR.
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