i started my shooting with a Logun S-16 shooting Ferals in barns and partially due to the barns being derelict theHad a similar problem a while back. We partially closed the three barn doors then my mate would go into the barn and fire a dummy launcher, this had the ferals take flight out of the barn door. Once the ferals were clear of the barn I would shoot a couple with a shotgun. We took it in turns on each of the barns and over a couple of weeks the ferals numbers were reduced.
Hope this helps.
ATB 243 Stalker.
Totally agree BSA R10 Mk2 .177 Now, Used to use FX Verminator .22 which can be adjusted to three different power levels, each shot taken at anything between 25 and 35 yards brilliant fun over the past 5 odd years with my boy learning his safe handling and back stops etc etc. Always took heart shots inside to make sure of clean kills and because of distance the pellet mostly stays rattling about inside chest, As a few old roofs are/maybe still contain asbestos so better not to take any chances......Sub 12ft/lb air rifles were made for this job. Nothing is better.