How do you tighten rifle stocks?

Answer 1

Best left to a gunmsith

Another answer:

Many rifles also have a stock bolt under the Buttplate which if the buttplate can be easily removed (some are not easily removed). There should be a large hole under the buttplate where you can see the head of a large bolt with a flashlight. Find the appropriate long-shanked screw driver & tighten the bolt. Stocks sometimes loosen up from shooting recoil. If you have wood shringage, swelling, warpage,wood rot, oil damage, etc. then take the first answerers advice.