This is the most common type of crack and place you find it. Being so common it is quite a straight forward process, except for the pin that I cant see if it is wood or metal.
To start this is the way I would tackle it but if you ask a dozen other people you will come up with twelve other methods. The first thing I would do is to remove that pin if it is at all possible and not making any more damage in the process. Next clean out the crack using a spirit Acetone etc. or Alcohol, you will also need some adhesive my preferred is slow set epoxy, dental floss. Bicycle inertube, Brass or Stainless Steel to make pins and staple's .Not totally necessary but it is the only thing I have found to successfully clean out cracks and make the passage of the adhesive and dental floss through the crack is a "Piercing saw blade.
When you have cleaned the crack out as far as you can go the dental floss comes in to its own now for pulling the adhesive into the crack as far as it will go, the reason for slow set epoxy now becomes obvious so take tour time. Now using strips of innertube bind the crack tightly so it closes.
After the epoxy has set clean up the wood and fit staples across the crack as in the photograph, the size ant type you use is dictated by where you can fit them without interfering with the guns working.
As for that pin, if you removed it I would replace it with a metal one but remember to file a small groove along its length to allow the adhesive to exit and not build up pressure. My personal choice would be to end the pin a little below the surface and steal a sliver of wood from inside the stocks head that will match in colour and grain then glue into the recess that you left over the pin then sand level with the stocks surface.
Hope this is of some help.
damascus
