Okay....So I had this same problem. I took the gun apart when I first bought it and the Gas Tube was extremely stiff and I couldn't pull it out. After trying to pull it off with pliers, I gave up and decided to shoot it and see if it loosens it up a bit. Shot it, took it apart to clean, and still couldn't pull it out. All I had to do was take off the hand guard and pry up on the tube a little against the end of the barrel and it popped right out. Goes in and out just fine now.. There is a spring on the end where the gas tube meets the receiver, it was just a little stiff from the factory.