Sure, a BB gun will absolutely kill a rat. And modern ones are so accurate you can easily make a headshot if your blind is less than 10 yards from the animal. When I hunt rats I use an Umarex Steel Force BB gun, set to 6-shot full-auto burst, with a red dot sight and in-line night vision monocular. Of course, I hunt them at night. And I bait the area to attract them. I dress in a ghillie suit and basically snipe the rats all night long from across the park, sometimes logging up to 18 kills a night! Although they are vermin, you would be surprised how soft their pelts are after processing, and you can actually find some cool instructions on the internet to craft clothing from them once you accumulate enough. Alternatively, there are amazing taxidermists who are creating incredible pieces from rats (I hope to learn soon!!). I hope this post shed a little light on rat hunting, and I welcome any new enthusiasts who read this to join our noble and honorable sport! Cheers!