I have a 1985 Mossberg 500 and am trying to replace the magazine tube spring. I have heated the thread end a little with a heat gun but it wont seem to want to break loose. I inserted a wooden dowel so I wont crush the tube and I am getting a good amount of pressure with a strap wrench but it wont budge. Does anyone know any other trick to get this thing apart without damaging the tube?? If I hit it with a brass hammer with a piece of wood over the cap end will it damage the reciever tube threads. Or would it be better to put some dry ice in it to try to shrink a little?