Reloading for Canadian 303 Ross Rifle

[tiriaq]

The chambers were deliberately reamed oversize in a misguided attempt to eliminate jamming problems. Some rifles were altered in a workshop in England. New production rifles were made with the enlarged chambers after the introduction date. There are different patterns of enlarged chamber.
FWIW, chamber drawings for the SMLE were revised in 1915 because of the same ammunition problems that affected the Ross.
Cases fireformed in a specific rifle could be treated as if headspaced on the shoulder, but this can be done with many calibres.