I've had to rewire my phone lines twice due to squirrel damage in the attic. So first I got this.
Air Force Talon SS, 22, using Beeman Kodiak, 21.8 grn pellets, it shoots really well, 3/4" 5 shot groups at 50 yards.
But is too loud. And up close, the scope is too high above the muzzle, 25yard zero, it shoots 8" low at 20'.
Now I use a TC Contender carbine in .22lr, using Aquila, Colibri's, 20 grn bullet at 300 fps, very quiet, like using a suppressor, and put behind the ear, or in the back of the neck, drops them with one shot. I'm up to 68 squirrels in the last 3 years.
Being urban tree rats I just chunk them, although my wife has forgotten to put up the bird food, and I've got some fat squirrels due that, may be good eating.