Well, I would have thought that if the OP has the sort of budget that would extend to a Service, he could afford a modern air rifle (I use a Weihrauch 35 & scope) for serious vermin control, & an 'classic', such as a BSA AirSporter/Webley Mk3 for pride of ownership/plinking/close range (15-20 yards or under) vermin control.
I would certainly doubt some claims for the power output/killing range of some older airguns. A well known book claims an early AirSporter could kill a rabbit at 60 yards with a head shot - this in the days of open sights. Hmm. I'm quite happy to use my Mk4 sporter for pigeons/rats at 20 yards & under with open or tele sights, or the Mk3 Webley unscoped at similar ranges, but no more.
Just my 2p worth.
Bru
Webley Mk3 x2, Falcon & Junior rifles, HW35x2, AirSporter x2, Gold Star, Meteors x2, Diana 25. SMK B19, Webley Senior, Premier, Hurricane x 2, Tempest, Dan Wesson 8", Crosman 3576, Legends PO8.