Here's what I did in my gunsmith shop. I suggest you do a trial run with scrap wood before repairing a good stock. I use 24-HR epoxy for the extended work time it gives me. Standing by was an air compressor with the adjustable flow nozzle shown in the photo. Mix the epoxy. GENTLY flex the crack open. We want to create a space for the epoxy to flow into. Apply the epoxy to the crack. Adjust air flow to a rate that moves the epoxy without blasting it away. You did experiment on scrap wood first...Right? Once you have nudged glue as deeply into the crack as possible release tension and allow the crack to close. Clamp lightly and allow to cure for 24 hrs. Refinish the area as needed.
Good Luck!
John
Good Luck!
John