The Hard Kicking comment, above, is one that always gives me the Willies when it is applied to an old, double shotgun, but, especially to a Charlin. There tend to be some things that dont get covered that are pretty important.
To begin with, almost all Charlins left the factory with 65mm chambers. When a Charlin is fired with proper ammunition, they shouldnt be hard kicking. Proper ammunition, sadly, is not especially easy to come by, and people have a tendency to buy what is easy to find. I wouldnt be in a hurry to use more than a 1 ounce load, in a 2 1/2 case, in the above 12 gauge gun. This is not a goose gun.
I have seen people firing a Charlin, and removing spent cartridges with the ends ripped off. Of course, there is a complaint that the gun kicks too hard. A Charlin is a pure over the center device that doesnt have additional mechanical locks built into the mechanism. Built into the opening lever is an interrupter, that keeps the gun from firing if the lever isnt completely closed. Spiking the pressure in a Charlin, with long, or, higher pressure ammunition, will occasionally force the lever out of battery at the shot. While the action cant be forced open, it is disconcerting, to say the least. These are very typically light guns intended for long days afield that feature much more walking than shooting. While they are heavily proofed, perhaps to excess, if truth be known, they are unpleasant to use with typical American off the shelf hunting or promotional loads.
Dealers, being dealers, have a distinct tendency to take things out of context when marketing their wares. I get a laugh when I see one advertising an incredibly smooth action Charlin,and perhaps writing how much better it must be than a Darne, because it is so smooth.
Poppycock. They are two different actions that accomplish pretty much the same thing. A Darne is not an over the center device, and the multiple mechanical bolts that hold it closed must be unlocked to open it, cocked, or, uncocked. If either gun has been fired, one, or both barrels, there is no difference in apparent smoothness, as those robust coil springs that drive equally robust strikers, have to be compressed, and that opening lever is what gives one the mechanical advantage to allow that to happen in either design.
I like a Charlin, but, I like a well broken in Darne R model better. Others feel differently. I dont find one to be superior to the other in a pure design comparison.
Good luck with the sale.
Best,
Ted