I did a search and he covers the R models very well but not the V models which are different.
Indeed, they are different. I've been asked about twice in 30 years how to do this. To be frank, your post leaves me wondering what the hell happened to this gun?
A Darne V is not what one would usually consider an amatuer gunsmithing project. Parts for your V model are almost non-existant in this hemisphere, and it would seem to me that there is a good chance you are going to need the services of either Kirk Merrington, who had, at one time, the carcass of a V model that a customer had had a go at "cleaning her up a bit", and lost some critical parts for the gun, which were never seen again, and abandoned the gun with him, or, Geoffroy Gournet, who has a few parts on hand for repairing the guns (I sent him some of mine, the only V parts I remember were trigger return springs, when he got into the importation of Darne guns, an endeavor which, lasted about a year if I am remembering correctly).
If the gun is going to end up at either shop, why not send it there, now? That would be my very first suggestion. The fact you are asking how to get the stock off a V leads me to believe you might be in over your head working on one. I'm not trying to insult you, just attempting to save you more broken/missing/unsalvagable parts, and some frustration.
But, I will tell you how to do it. Remove the breech and the barrels, and you will see, down in the slot the breech slides in, a screw, which, is for the triggerguard. Remove this, and the screws from the tang of the triggerguard. Unthread the triggerguard and remove it. This will give access to a screw that is underneath the triggerguard, facing up into the action. Remove it also. It is threaded into a wedge that will slide up and out of the action (put a pencil witness mark on the front and top, so you get it back in the same way) and, behind that, will be the screw that holds the wood to the action. A very few pre Bruchet guns had a 10mm bolt under the buttplate, mostly double rifles built in potent calibers. Most of the Bruchet guns have the bolt, rifle or shotgun. You still have to do what I posted, above, before you remove it.
All of these screws have a thin gunsmith slot, and can be easily damaged. There is a good chance the wedge will be seized, and require some time and effort to get out of the gun. The threads of the stock screw are lubricated with lard when you put it together, and, it has to be tight. These guns have been built, by hand, for over a hundred years, and don't be surprised if there are subtle differences between what I say is there, and what is actually on your gun. This will get you started in the right direction, however.
I wish you good luck with your project, but, I really wish you would put it in a box and send it to Kirk. No offense, it just always seems to end better that way.
Best,
Ted