Right then; for those of you that are interested, my restoration gunsmith/importer/good friend Steve Bertram www.bertramandco.com has come up with some original ".275 Bore Rigby Special High Velocity Rifle" cartridges.
When I get out of our "deep freeze' Winter here I will take my .275 Rigby Mauser out and test fire 3 shots over the LabRadar to tentatively settle the question of no kidding ".275 HV for Rigby" muzzle velocity in real life.

As soon as this is done I will certainly post the results.

Who wants to go in on a betting Calcutta as to actual average muzzle velocity?

(just kidding, too hard to deliver a bottle of Single Malt to the winner)

- Mike