Gun barrel calibers range from about .17 to .80. While certainly not as powerful as a larger-caliber firearm, a .22-caliber gun can inflict lethal damage to humans in a range of up to several hundred yards.
The .22 long-rifle rimfire cartridge is the most commonly used ammunition worldwide, originating in the mid-1800s. Rifles and pistols come in this caliber and range in effective accuracy from a few dozen up to a few hundred yards. "Drop," wind and other factors can affect a bullet's trajectory, even at close range in an open area.
The Bullet Matters
Standard plain lead bullets travel with less velocity than copper or gliding-metal-plated ones. Plain lead bullets may also leave residue in the barrel, which can oxidize and lead to problems with loading and firing.
"Low Power" by Reputation
Most firearms are more powerful than a .22, but "relative low power" should not make owners underestimate potential danger. Humans and large animals can be killed with shots to the head or other critical areas from hundreds of yards away. From close range any shot can cause life-threatening blood loss. Birds and small mammals are unlikely to survive any direct shot or a close-range ricochet.