Not long after acquiring my pre-WWI Rigby .275 (chambered for the ".275 Rigby" cartridge) I pushed the load development and got to around 2980 fps IIRC before (very) slight resistance to bolt-lift after firing. I was chasing the published 3000 fps with the 140-grainer, just to see if it could be done with modern powders, but I am fairly conservative so after discovering that was the probable limit I have since backed off to a bit under 2950 fps as a working load.
Barrel is only 22 inches. Reckon I would have safely achieved 3000fps with a 24-inch barrel, but that's just a number...
Not worth pushing it on hundred-year-old rifles!