I have a RRS clamp for my Manfrotto 055 and I've used it for my Vulcan as well as most of my other airguns. One is a Uragan King but it isn't suited in a clamp as is due to the double bottles.
This RRS clamp is okay but the rubber on the clamping surface makes it flex a tiny bit in the clamp, also this tripod isn't all that stable either in spite of its quality, rather I think it's because of it's load rating.
Which is the opposite of this Fat Bot 42mm and leveling head. Only about 1/4" of wobble at 100Y with me holding the gun getting ready to take a shot. The best money I've spent on a product in years. I highly suggest going with a ARCA or Picatinny head of some kind to avoid that spongy feeling when clamped.
Here's the Fat Boy. I wanted a tripod and head like this for a decade but didn't want to spend RRS money and this set up was what I envisioned both price wise and quality wise. I paid almost half what the RRS equivalent would have been.