The Gamo Outdoors USA Squirrel Master Classic gave me a good chance to see if air rifles have enough power to cleanly bag "squag" (that's what my friends in central Pennsylvania call 'em). After witnessing 100-some squirrels succumb to the Gamo Whisper Fusion Pro, I can say they do. I can also tell you an air rifle, whether it be a .177- or .22-caliber model, is no .22 rimfire--so you have to be selective with your shot placement.
According to data from CCI, its SGB .22 LR load drives a 40-grain lead flat-nose bullet to a muzzle velocity of 1,235 fps for 135 ft.-lbs. of energy at the muzzle. Gamo says its 15.3-grain, .22-caliber Hunter lead round-nose pellet, fired from the company's Hunter Pro rifle at a velocity of 676 fps, produces almost 16 ft.-lbs. of muzzle energy. Surprisingly, even though the .177-caliber Hunter pellet weighs just 7.6 grains, it produces almost 17 ft.-lbs. of muzzle energy, thanks to a higher velocity of 943 fps. Still, that's roughly 88 percent less energy than the CCI .22 LR load.
Note these velocity and energy figures are measured at the muzzle, where they are the highest. At squirrel-shooting ranges, they will be less. For example, using the above-mentioned muzzle velocity, the .177-caliber Hunter pellet retains 874 fps and about 14 ft.-lbs. at 10 yards, and drops to 759 fps and not quite 11 ft.-lbs. at 30 yards.
A head or neck shot with a pellet designed for hunting will knock a squag flat. Jacob Landry from Swamp People demonstrated this over and over again at the Squirrel Master Classic. ("Granddaddy always told me not to choot 'em in the meat," he said.) A hit elsewhere in the body may require a follow-up shot or two--and some pellet-plucking to prepare the squirrel for the plate.
This may be obvious, but use a hunting-style pellet when hunting. Gamo makes several like the Hunter, Magnum and Red Fire designed to expand on impact and maximize damage to vital organs. Squirrels may be small, but they are tough. When you're going after them with air rifles, think in terms of big game. Choose a good bullet, and then place it precisely.