I have an RWS M48 in .177 - that's generally regarded as one of the better mass-market air rifles, with an advertised velocity of 1100 ft/sec. My chronograph verifies this velocity with lightweight RWS "Hobby" pellets.
Using the more accurate but slightly slower RWS "Superdome" pellets, five shot groups at 40 yards can be covered with a dime. By 50 yards - it takes a quarter, and beyond that, well, lets just say groups open faster than the range does, so it's unsuitable for making precision shots on vermin beyond 50 yards. (I've read that lapping the barrel helps, but I haven't tried that yet.)
I think it will take a larger pellet if you want a 100-yard vermin killer.