Couple additions to the above, thanks Max and Redroth. The trunnions on the side of the Russian and Finn Maxim barrel extension are a larger OD than the hole in the Vickers recoil plates and require turning down to the correct size to fit and moving them slightly. This is the operation that I have a machinist do for me which requires three or four axis CNC mill. The reduction of the muzzle to the correct OD for the Vickers is straight forward. Muzzle needs to be correctly threaded for booster cup. The tops and bottom of the barrel extension need to be milled off slightly as well.The short answer is yes. Bob Naess provides a service where he mills the Vickers .303 lock extractor to accept the 7.62X54R cartridge, grinds and profiles the .303 feed block a little, and has a machinist thread the end of a 7.62X54R Finnish or Russian Maxim barrel and modify the breech area to fit into a Vickers. It is an elegant solution and I had Bob do it for me a few years ago. He has done many of these conversions.
I believe that BarrelXchange (Troy) also does a similar and less expensive conversion but instead of using a Maxim barrel he reams the standard Vickers .303 barrel to 7.62X54R.