I've used JB Weld Steel stick and mixed it with a little 5k lb expoxy to make it a it more malleable,but not runny. Takes a little practice but once it sets, well, it's like steel.
On another topic, flimsy synthetic stocks make me crazy, I've found that the hollow spaces in the forend can be filled with epoxy or fiber reinforced fiberglass. No twisty, floppy feel any more. Makes te forend heavier, so I get some old lead bullets I won't be using and put them in the hollow buttstock until the rifle balances were you want it. If you don't want them rattling around, put them in a baggy with some epoxy and stuff the baggy into the stock. It'll come out if you need to adjust the weight distribution.