Raimey, no idea what it's called, never seen anything like it by another maker and the same can be said for every gunsmith I have ever showed them to.
The top lever spindle, as it is moved to the right to open the gun, pulls back a rib extension that fits into a slot on the barrels. When closed the real top rib and the rib extension meet a tight fit about a quarter inch towards the muzzle from the breech end of the barrels.
I don't know enough to describe the inner workings of it but I do know the design results in the wood of the horns being extremely thin and prone to cracking at the lower edge of the receiver's rearward extension.
If you look at the pics of the Russian example you posted, you can see the crack. Mine cracked in the exact same spot on both sides. I have similar actioned Piepers that don't have the rearward extension of the receiver and while the wood is also thin, they don't seem to crack as easily.
Last edited by canvasback; 12/11/16 03:37 PM.
