You could safely use .303 British starting load data to develop 7.65mm loads. The max. loads for the 7.65mm will end u[p a little hjotter than loads for the .303. The 7.65mm case holds a little more powder than the .303, and most .303's don't lock up on the front end of the bolt like a Mauser does.



But if you mean can one use .303 ammo in the 7.65mm chamber of an 1891 Mauser, NO! The .303's rim will not fit the Mauser bolt face, and the chamber dimensions are somewhat different. The Belgian (Argentine) case is bigger in all dimensions except the rim, which is .470" or so for the Mauser case and .540" for the .303, whereas the .303's head is only .460" and the 7.65mm's is .468" - a little too big for shooting .460" diameter cases. Now that Graf's has reasonably-priced 7.65mm brass, why mess with such a thing?

no I have no barrel and was thinking about rebarreling it to 303 British. I checked the bolt and it looked like it could be opened up to the 303. I was just wondering if anyone thought the action would take the preasure.
Dean

The action is certainly capable of handling normal 303 pressures. From a functional standpoint, the difficulty would be in correctly modifying the mauser magazine to handle the rimmed 303 case reliably. I think it could be a fun project (if you didn't have to make money doing it!). Regards, Bill.

It can most likely be done.
There is however no reason to do it.
It will be too much trouble and 7.65X53 is a superior cartridge anyways.

-Spencer