Originally Posted by Quentin
Great answers, TekGreg!
Just repeating some of the points, you probably can get a midlength gas system to work with a barrel shorter than 14.5" but it would take a lot of tuning to make it reliable with various ammo, increasing the gas port and playing with the buffer weight and spring, maybe even a light weight bolt carrier. Even in a 14.5" sometimes it's hard to get Wolf and other light powered ammo to be reliable with midlength gas.
It's just not worth it so you see the carbine length gas in shorter barrels.
Quentin, absolutely correct, from what I can tell. The more tuning you do, the more specialized the platform becomes and the more finicky it will be about accepting types of ammunition and bullet weights. Manufacturers have to make a gas system that will devour every known weight/powder combo on the market and therefore are extremely limited by what can be put on a production gun.
“Malo periculosam, libertatem quam quietam servitutem." (I prefer the tumult of liberty to the quiet of servitude.). Thomas Jefferson
"All that is necessary for the triumph of evil is that good men do nothing."
-Edmund Burke, Loosely translated from Thoughts on the Cause of Present Discontents. (1770)