Unlike many American or English doubles, A V grade Darne is not just the standard grade action with more features and embellishment. It is a completely different action with no parts interchange with the more familiar R action. A quick trip around the world wide web that Al Gore invented will get you instructions on how to take down an R action, but, little is out there on the V action.
A quick way to tell from a distance if you are looking at a V is the sliding tab safety, always located in the watertable, under the sliding breech. I called it a watertable because I know Wonko doesn't like it, and, besides, that's what they call it in France. A true P action gun also uses the same safety in the same location, but, there are subtle differences I'll get back to. Very early (1894) patent Darne R models, and Darne clones built on that patent have a rocker style safety in the same location, but, it would be hard to confuse that with a V sliding safety.
To get the breech block off, you must open the action, and bring the opening lever to a straight up and down position. A V action breech block moves proportionally with the lever, as opposed to an R, in which the lever is opened all the way, and then a tug on the lever slides the breech back.
Once you have the V gun with the opening lever as shown in the photo, you must pull straight up on the lever, keeping the lever in the same position you moved it to. You are in the process of overcoming the tension on the main spring of the V actions opening lever, and if it has been a while since the gun was taken down, it can be quite hard to disengage.
This photo shows about how you grab the lever with your fingers to exert pull on it. I usually throw my free hand and arm around the top of the butt stock in a bit of a bear hug to hold it while I'm tugging with the other hand.
When you have over come the spring tension, you will get a bit of a "pop" noise, and you can carefully move the lever completely out of it's slot like this.
I like the lever completely out, as there is less chance of it marring the comb as you carefully slide the breech off the rails.
This photo shows the breech removed from the V action, and the pen is pointing to the button that must be depressed and held while dismounting the barrels. The barrels on any version of a Darne are an interference fit, and you must break that tension to remove them. The guys at the factory have a piece of masonite hung on a verticle wall near their bench, and just jam the muzzles into it while holding the button. It sounds brutal, but, they aren't hitting the buttstock that way, and don't risk breaking the toe of the stock by hitting it with a karate chop while the muzzles are in carpet or the tip of a shoe.
This last photo shows a view of the axle (tip of pen is pointing at it) and the main spring, in the bottom of the opening lever, the tension of which you overcome when pulling up on it. That spring is the heart of a V action Darne, and the gun will be useless if it breaks, so don't be tempted to jam any tools into the breeck block to pry on it. Assembly is just the reverse of what you just did. Be careful to line the slot on the opening lever up with the axle once you get the breech slid back on the rails, and push down firmly on the opening lever until you hear a nice little "click".
Once upon a time (pre-1965) there was a different large key action known as the P. The P action is similar externally to a V, with one critical difference-the breech block was not easily removed. On most of the P guns I have seen, the safety button has a profile that is pointed at either end, and the opening lever is actually a two piece affair, clearly visible when the gun is closed. There do exist guns from the P grade series, typically grade 17 and 18, that are so marked, but, are built on a V action. I've also seen a few James Wayne imported grade 18 guns that are R actions.
Regis Darne considered the 1909 V gun his masterpeice, and they were always priced higher than an R. The R, of course, sold in much greater quantities, and is typically what we are talking about when the discussion is about a Darne.
I prefer an R for actual use, but, there is no denying just how beautiful even an average V gun really is.
Best,
Ted