I regularly use my BSA XL Tactical .25 for ferals and rats around farm buildings - fitted with WTC 1.5 to 5 x 20.

Accurate to 30 metres as long as you can get the distance right - 1" groups @ 30 metres is usual.

Had to go thru a lot of different pellets (and size them) to find best match - ordered several .25 calibre pellet ranges from the US, such as H&N Wadcutters that REALLY blast the ferals and rats off the rafters.

I stick with H&N Wadcutters, BSA Pylarm and Paragon Z25's.

Happy to send you a range of pellets (20 of each) if it helps you find a good match. Do you have a sizer, in case they're too tight in the barrel - BSA barrels way too tight generally for unsized pellets.