 From the center of the gas port to the muzzle, the longer you can make that, while it makes sense, the longer the gun is pressurized. And remember, what you're doing when the gun is cycling is you're moving mass. Now, if you want to move a couch across the room, do you walk up to it and you kick it, or do you get behind it and you shove it? If you want to move mass, shoving it