We should not mix another cartridge here, 6.5x52 Rimless (6.5 Italian Carcano) which is military and something else entirely. But 6.5x52R (as made by Norma, RWS, S&B) and .25-35 Winchester are one and the same thing, which is confirmed by all standard references starting from Cartridges of the World. My rifle will chamber both of these rimmed cartridges normaly.
With kind regards,
Jani