Cyanoacrylate glues are very strong in tension, but weaker in shear. For clean wood, Titebond II wood glue is tough to beat, but you'll need compressed air to force it into a crack. I tested various wood glues several years ago on small blocks of planed black walnut. The Titebond II was stronger than the wood when I attempted to break it apart after a couple weeks, as was Acraglas, and a Marine Epoxy. A polyurethane glue I tried was also very strong and gave a glue joint that was hard to detect, but it was messy to work with and affected finishing of the surrounding wood if you couldn't sand off what squeezed out of the joint. I have read that polyurethane glue works good when there may be traces of oil left in the wood.
The Titebond II gave me the most invisible glue joint when finished with over half a dozen various finishes including Tung oil, Permalyn, Spar Varnish, Oil Modified Urethane, Polyurethane, Watco Danish Oil, Tru-Oil, etc. With careful grain and pore matching on my test blocks, it was almost impossible to detect a closely fitted joint. For a cracked stock with no missing wood, and careful clamping, you can make a repair so invisible, no-one will ever know it was broken. This is what I was looking for. Many repaired stocks may be strong, but the glue joint sticks out like a sore thumb. I did not even test any of the Super Glues because I knew they were not ideally suited for the shear and flexing type of forces required for a lasting bond in a gunstock.
