A very high-powered conventional air rifle in .22 caliber will launch a 15 grain pellet around 700fps providing about 16ft lbs of kinetic energy at the muzzle. Conventional pellets are very poor projectiles and the velocity bleeds off very rapidly. 400-500 yards downrange the pellet is considered to be harmless. Small game can be taken out to about 35-45 yards if the shooter is very proficient and can make head shots. Body shots, even at closer distances can result in lost animals.
A typical 22LR bullet weighs about 40 grains and leaves the muzzle around 1100fps for around 107ft lbs of kinetic energy at the muzzle. The bullet is a pretty decent projectile and will be dangerous out to a mile or more. Small game (such as squirrels) can be taken with body shots at distances primarily limited by the shooter's ability.
There is a world of difference between even a very powerful conventional airgun and a .22LR rifle. The short range of the air rifle is a considerable advantage in crowded areas while the .22LR has a huge advantage in range and power.
Re-using pellets is not really feasible. Even if they are not damaged upon impact, the skirt is typically deformed by the blast of air that sends them on their way.
All that said, I think it makes sense to have an airgun. Pellets are cheap. You can store a LOT of them in a very small space and they never go bad. I suppose you could even cast little lead balls from recovered pellets if things got really bad.
Last edited by JohnKSa; May 25, 2006 at 11:22 PM.