If all else fails, TW Chambers says they have Beeman R8 .22 barrels in stock:https://www.gunspares.co.uk/products/24865/R8/
22 cal barrel for the Beeman R8 --BRL014 is the same part number for the new hw50 rifle too !! Looks promising now as an easy swap. I also noticed the cocking lever,shims, detente and detent spring and wood stock for both rifles are the same. Even the piston seal for both new and old HW50s and R8 is the same!!26mm ?? I thought the old 50s R8 was a 25mm size and the newer hw50s is 26mm.Chambers shows the same part number for both?
Also Beemans R6 is the newer HW50s.YEt all piston part numbers are the same PO68 and the same seal. Maybe they made a mistake. Trigger guards are the same too for the R8 and newer 50s .
...Does anyone know if the actions will fit each other's stocks?
One thing I can tell you Dan, the old R8 barrel was 18.3" long or 465mm with 12 groove rifling. That shorter barrel sure looks like the newer HW50s or 99 or R6 . And that confused me. By the way BRL-014 is the 22cal barrel ,and BRL 012 was .177cal
... I contacted Weihrauch with the serial number on the barrel to see if they can clarify.