The good news is this is a fixable crack. You need to use liquid type acraglass (not the gel!!!) as the liquid will penetrate the wood fiber.
First degrease the head of the stock. The more oil you get out the longer the repair will last. I degrease with dollar store oven cleaner keep applying this until it stops turning brown. Then remove the residue throughly with acetone. (make sure the stock dried out after this)
Second mix your acraglass liquid (4 to 1 ratio) you will then need to warm this mixture up slightly to increase its viscosity, a hair dryer works well for this and it only takes a few seconds until the glass gets really runny. (this helps increase the penetration of the glass may sound like overkill but it really works)
Third apply to the cracked area and let it sit for a minuet or two until the glass starts to cool and becomes little thicker then apply some more glass, clamp the crack closed, and walk away for 24 hours. This will require some clean up work to remove the excess glass once it has hardened but that can easily be done with a small scraper inside the inletted area and some sand paper on the outside.
good luck
