The point is, it doesn't really matter what you do. You can blow the gun up, setpos it to a distant point, make it setcaptive or whatever - you can choose anything that suits your mission. The important thing is that when the loon dies you can do anything you like. Obviously the countdown is whatever looks best in the circumstances. (Thinks: wonder what happens if you moveInGunner a gamelogic?)
There is a script in the Ed Depot which gets another loon to get into the gun. So if you have a good position you can snipe the enemy platoon one by one as they get into the gun ;D