That's a great gun. Yes you will damage the barrel threads if you shoot it with no choke tube fully seated in place. I say shoot anything out of it except steel. If you must shoot steel be sure you have a choke tube specifically designed for steel, then it would be OK. If the box of shells does not say what the shot is comprised of, then it is lead shot. Other than steel you can shoot all other shot out of your gun with any choke tube in place and not damage the barrel or choke tubes...<><.... :grin: