The breech block on a Charlin has a round pin with a set screw holding it in, from the bottom of the action. The stock needs to come off to get at it. It is not an easy to remove design, and, further, there are two TINY, and I mean really tiny, springs and detent balls (bearings) that the breech rides on. I damn near lost mine when I took my Charlin apart, and I knew they were there.
Most of the screws in the breech block (two are visible on the bottom of the breech block, when the action is all the way open) have some metal peened over, to keep them from coming loose.
If you are beginning to think this sounds like a lot of work, you are getting the picture. There really isn't a good reason to dismantle a Charlin breech block, unless something is broke. The thing that usually breaks, is a flat spring that serves the purpose of keeping the action from trying to cock itself if it is cocked. If this spring is broken, the opening lever will make two distinct "klunk, klunk" noises when you are opening it, if the gun is cocked. I used to have a few of those springs around, but, they are easy to make from flat spring stock.
If your gun is not doing this (opening should be smooth as silk and nearly silent, when the gun is already cocked) I'd suggest you not take it apart.
There isn't really a good reason to if the gun is not broken. Trust me on that.
Best,
Ted
