You've tightened everything that holds the stock on. If you still have a loose stock at this point, it is time for stock removal, oil removal from wood, and a glass bedding.
IF you believe this is needed in your case, get it done, soon-you don't want to try to have a Charlin re-stocked.
For some strange reason, people think they have to pour oil into an action to lubricate it. That causes much woe for the wood.
Good luck with your Charlin. I see much ballyhoo on the internet about how superior they are to a Darne ( BS, in my opinion) mostly from dealers that haven't a clue what a Charlin is, what grade the gun they are peddling is, or what one is worth. I find them to be good, serviceable sliding breech guns with an interesting design.
Best,
Ted
