Doesn't cutting an AR barrel require some fancy voodoo on the gas tube hole (sorry if that's not the technical term) unless you want to risk $#@!ed up dwell times, not enough back-pressure, etc?
I can cut off the end that attaches to the upper receiver shorten the barrel then weld the attacment point back on for a case of beer.
Or some ding dog wants to use a carbine barrel for a pistol build.