I inherited an old Marlin Model 39M 22 that originally came from Florida. It is pitted pretty badly along the barrel. I want to draw file and sand the Octogon barrel but I haven't been able to extract the front site from its dovetail. The site is not rusted on the outside but I think it is probably rusted in place inside the dovetail. I've used liquid wrench and WD40 as well as mild heat to try and loosen it to no avail. Any suggestions?