A quality pellet gun with a . 177 caliber pellet and a minimum pellet speed of 1000' per second (FPS) is adequate enough to kill rabbit, squirrel, mongoose and other small game. Shot accuracy and distance help determine the lethality of the shot as well.

Will a pellet gun hurt a squirrel?

It will certainly sting a squirrel and likely keep him away but is not capable of killing it. Shoot for the hind quarters. The BB will sting for a while but the squirrel will recover with no permanent injury.

Can I shoot squirrels in my yard with a pellet gun?

unless you have a "nuisance wildlife control license" (or something like that), you can't kill them. only ground squirrels is considered as pest animal, you can kill them any time of the year. different cities / counties have different regulations on discharging pellet guns.