I just acquired a used winchester 1300 28" barrel. shot it for the first time yesterday and after about 10 shots the vent rib on the barrel started to slide forward. it was about 1.5" in front of the barrel. i know winchester has a floating vent rib, but this isn't normal is it?? should I just have a local gunsmith look at it or is it something i could fix myself??? Thanks for any help ya'll can give.