I agree, airsoft is not suitable for pest control. An actual air rifle is the way to go. This is also likely to be a cheaper, as well as more effective solution (especially if you look at second hand options).
Anyone seen this yet? I had heard that they were doing a GBBR, but hadn't heard about this one, Not a bad price either.
https://www.taiwangun.com/assault-rifle-aeg/we13-13-m4-ar-15-airsoft-rifle-30-rps-etu-tan-well-pro