..what for? is the old one damaged, want a longer/shorter one..? Personally, I've never had the need to take mine off, but if I did, I guess I would use a smithy.
The tube screws out, standard right hand threads. Beware of locktite and be ready to catch the follower and spring when the tube comes off the receiver.
The tube is glued in so you have to heat it to break the Loctite. A heat gun works pretty well for heating it up to break temp. You turn the tube with a strap wrench applied at the cap end. If you try the strap wrench at the base you run the risk of crushing the tube. Hold the receiver in a padded vice while heating and turning with the strap wrench. At some point you should be able to use your hand to finish removal.