If I could only own one gun it would be a Model 12. That being said, there are a couple of things you might do before ordering parts;
a) completely disassemble the action, clean everything thoroughly and reassemble. Don't forget the ejector! Also be sure to grub out all the old oil and seeds that get caught and conpressed in the bolt locking notch on the inside top area of the receiver. If the trigger group does not want to come out you may have to loosen the stock slightly. If you have to do this, you may want to remove some of the wood in the half round area of the stock directly behind the trigger group securing screw. This will allow the removal of the trigger group anytime without loosening the stock.
The Model 12 is quite easy to work on, but, years of old oil and seeds and field residue can cause problems after 50 or 60 years. The same goes for the Model 42.
Good Luck and Congratulations on getting the Model 12!
