Originally Posted by drgonzo
You use the length of barrel you want to and don't answer to idiots. If you have specific considerations in mind, then you try to meet them, but no barrel is inherently wrong if you straight up like it better. For any reason.
That. In theory a longer barrel will be less air efficient but the difference would be pretty minimal, use what you are most comfortable with.
Personally I use a 12 or 14 on everything, anything longer gets unwieldy in my opinion but I've seen plenty of people rocking 16s with no trouble. Do what you like.
I would say that 18 is probably way too long to be comfortable to most people.