I recently inhereted a Ranger 20 Gauge pump action shot gun. I pretty sure its a Sears House brand made by Stevens (520A) with the double hump receiver. The action will not open with the release. This was my grandfathers shotgun he hunted with Its a good clean shotgun and actually feels pretty good in the hand. Its a very early model with the safety in the trigger guard ahead of the trigger sort of garand or M1A style. I know how to take it down, It is a takedown by turning the magazine tube out. But the action has t be open for this. A disassembly diagram or parts break down would be helpful. I want to fix it and would also like any ideas on getting the action to open So I can get it apart to see what I need. It looks like Stevens 520 parts will work in it from what I have researched so far. ANy and all information is welcomned