SX-1's that have not been cleaned properly will develop a ring of corrosion where the piston head sets on the mag tube.......turning it around gives you a clean, smooth surface for the gas piston to move on the mag tube again.
Definitely heat. Kroil will not loosen the loctite that's on it. A heat gun or good hair dryer and a strap wrench as mentioned.
To b12, even if you do clean your gun well and often, the simple movement of the piston will wear the area of the outside of the mag tube over which it travels. Since the mag tube is symetrical on both end, you just turn it around and you are good to go for a while.