An educated guess would be that your carbine is chambered for the Egyptian cartridge. The Egyptian and Beaumont cartridges are so similar that cartridge collectors have difficulty telling them apart without a head stamp and many early cartridges were not head stamped. The importance of early military cartridges is that they chamber in the rifle/carbine and fire. Not much reloading going on back then. Also, the only Rolling Block carbines chambered for the Beaumont cartridge were made by Nagant in Belgium under contract by Remington. They were originally chambered for a straight-walled cartridge and later re chambered by the Dutch for various versions of the bottle necked Beaumont cartridge.
Nice looking carbine; no Egyptian markings on the barrel?
Is the OWS ammo made from .50-70? I had some made by ??? from .50-70 many years ago and all the cases split on firing. Decided Bertram was a better deal.
Saddle ring carbine identification
Re: Saddle ring carbine identification
What markings on the rear sight? That is a pretty hefty cartridge for a carbine.