So...There I was in the basement, playing around with my A1 build, when I saw a rabbit hop his way past the window...

I look at the A1 I'm holding.
I look at the rabbit.
I look back at the A1 I'm holding.
I look back at the rabbit.
Hmmm...

So.  Before I go spending any money on a hunting license, has anybody here taken an AR-15 rabbit hunting, and do I NEED dogs to do it?

My first impression when handed an M-16A1 was that it would be the best rabbit gun ever.  Not the most charitable sentiment under the circumstances, but still very true.

Being from the frozen north we never used dogs to rabbit hunt - and frankly I've never seen the sport in that.

In brush at short range, I agree the .22LR would be more than adequate, but in more open country the flatter shooting 5.56mm is nice to have and the AR-15 is more accurate than most .22LRs once you get past about 50 yards.  

If you are going to eat them, head shots are the rule - and for best eating gut them on the spot as Cottontails will go bad quickly otherwise.

I've seen 5.56mm literally blow rabbits in half...Just something to think about if you DO plan on eating them.

+1. It might gut it for you also. But fun factor is a 10!

If you use a 5.56mm, use an FMJ and eiither keep the velocity down or stay with head shots under 150 yards (until the velocity drops off enough to prevent the bullet from fragmenting).  

When hide hunting for coyotes, we'd use a very light jacketed 50 grain SX that would go in one side and then fragment - preventing another hole in the hide from an exit wound.  But if you apply that strategy to a rabbit you get rabbit burger.

my pwa commando never misses a rabbit hunting trip, or miss the rabbits either

Yup.

68gr Hornady BTHP at about 150 yards. I was a little shocked at the damage.
This was a jackrabbit, too, which is kinda big.