[Clutch Martin]

The AR-15 in 5.56mm is a .22 caliber, might shoot straighter over distances... but it’s a .22 (.223 to be more exacting) nonetheless.

[libstripper]

I have a S&W M&P 15-22 that regularly shoots groups like that at 75 feet. Since it took him 150 rounds to do the job, I suspect he used a similar rifle.

[Kickass Conservative]

I own one. I was being facetious. #;^)