+1
To add to the discussion; the appellation ".275 Rigby" is a fairly modern adaptation of the cartridge name. Originally was known as the ".275 Bore cartridge ….. for Rigby Magazine Rifle" or "for Mauser-Rigby Rifle"
The "HV" was simply to set the 140 grain bullet at 2800'/sec apart from the "standard" loading 7x57 Mauser (or .275 as known in England and the Colonies).
The only apparent difference in the rifles was how the iron sights were filed in for the specific loadings and then engraved/stamped with the proper cartridge info.
- Mike

ADDED:
Removed the stock & measured the action, it is almost assuredly a "standard length" commercial action.