I call it the 25 Nagant Single Shot. I'm betting on a 70 grain bullet at over 2400 fps. It would make a sweet vermin round. The parent case is a 7,62 Nagant Revolver case. The 25-20 Winchester is tossed in for scale. I may be getting a reamer made for this one!~Muir
Or for a more familiar comparison, the Hornet.