I just repaired a Turkish Mauser stock that was broken all the way through one side, where the recoil lug goes through. I have only put 2 rounds through the rifle since I did the repair, so I can't be sure how it will hold up. I had cheap ammo problems. Maybe a firing pin problem.
I used Brownells Acraglas Gel to glue the crack by spreading it and forcing the gel into it with a stick. Then I supported the ends of the stock and put a weight in the area of the repair to hold it closed. The next day, I trimmed off the extra cured gel. Then, I drilled a hole from the area of the indentation for the trigger gard across the crack, and installed a 2" long brass 6x32 machine screw in the hole with more Acraglas slathered all over it. The hole I drilled was not very tight, but tight enough that turning the screw pulled it down into the hole. Before I installed the screw, I cut off the head and filed a screwdriver slot in it. One end of the screw is covered up by the receiver, and the other by the trigger guard. I think I was very skillful (lucky) to drill the hole without it coming out through the stock, where it would show. It worked this time. I'm not sure if I could do it again.
And, like I say, I don't know if it will hold up or not. The crack is in the worst possible spot I can think of. If you are unable to spread the crack you have, like I did on mine, the Acraglas comes in liquid form too. That might work better for you than the gel. I have also heard about using air from a compressor to force glue, or whatever is used, into a crack.
Good luck.
Verne