Is 300 BLK a Good Caliber for the AR Platform? Aaron Cowan covers that in his review of the Sig MCX TacOps rifle in 300 BLK.
This Battle Arms Development SBR is not your typical AR 15, not least thanks to its superb aesthetics. Check out the Battle Arms Development Paratrooper.
Most hunters approach varmint hunting from a distance. With a bit of practice, though, animals can be called in close. That's why I'm carrying two rifles, one for long range shots and one that fires subsonic rounds for closer work.