I have fixed broken stocks quite a few times, but without seeing the gun personally it's impossible to ascertain the best course of action. That said, I suspect that the pin is causing problems and needs to either be removed or cut off shorter inside the crack. Before doing that, survey how the locks and tangs fit. The lock seems likely to have some gaps, no? If that is the case then proceed with getting the metal pin out of the way. Now you should be able to close up the gap, although it may take some force. Don't try to use a metal clamp, like a C clamp as it will likely damage the wood and just slip off any way. I have used long strips of bicycle inner tube for clamps. Free, they won't damage the wood and you can apply considerable force with them by just wrapping the stock tightly. Shellac and then heavily wax the stock before applying epoxy and you'll keep clean up to a minimum. Don't mix the epoxy with anything as it reduces the bond. Apply the clear epoxy, wait a few minutes to allow it to soak into the grain, then add more epoxy and wrap. Any cosmetics like matching the color and touching up the checkering can be done later. Here are a few pictures of a stock that I did recently.


Men build too many walls and not enough bridges. -Isaac Newton