[RightFighter]

You mean a real AR-15 with a conversion kit to shoot .22 ammo? I didn’t know there was such a thing.

[BipolarBob]

http://www.ar-15.us/22_kits.php

[Ouderkirk]

You can buy a real AR-15 and get the conversion kits.

Replace the bolt carrier group with the one in the kit, and you’re ready to go.

http://www.armalite.com/Categories.aspx?Category=e12e2236-9dab-4a1a-a015-47b56da84038

Is but one example of these conversions that apply to the entire platform.