This gem bought to you by AR15.com, a giant forum that sometimes talks about guns.
The 5.56 round is practically harmless unless it fragments. Reliable fragmentation velocity is about 2600 fps.AR15.com User Pebble LINK
Your barrel has a muzzle velocity under 1900 fps, which means its effective range is zero meters. You could shoot someone with it point blank in the chest and they’d likely be fine, unless you happened to get lucky and strike the spinal cord. If you had used an 11″ barrel, you would probably OK for 30 yards or less…or if you had used a .300 blackout, you’d be fine with that barrel length.
At least the first person to respond to him responded with laughter.