There is no center rod in the wrist of a Charlin. It is this steel rod, wood screw threads on the outside, and machine screw threads on the inside, that frustrate bending of a Darne stock. There is a good picture of what you are up against, with a Darne, here:
http://www.gournetusa.com/forum/topic.asp?TOPIC_ID=76That big steel rod isn't a Charlin feature. That is the good news.
Having said that, I've seen many Charlins that have cracked wood in the wrist. The great majority of those have the semi-pistol grip. If the gun features a straight stock, it would likely be easier.
Good luck. Let us know what happens.
Best,
Ted