Rodents and small game.
Definitely Yes it can.
When you say Air Rifle you are referring to a pellet rifle not a firearm. At present there are no 300 Cal air rifle being made.
Small game like squirrels, rabbits and rodents.
Yes it is possible. An air soft gun will not kill you but a pellet rifle is capable if killing a person. Pellet rifles come in several calibers. .177, .20, .22, .25, 9mm, 45 cal and 50 cal. The last 3 calibers are fired from a PCP pellet rifle. This rifle (PCP) uses a scuba tank to charge the rifle with 3000 psi of air. All of these pellets are capable of injury or death.
It all depends on the rifle, pellet and power source.
No, no air rifle has a capablitay to kill a deer. The maruader is a great gun but it can only kill up to a rabbit or mabye a fox. If you try to shoot a deer with that it will charge at you or it will just shake it off.
OKAY: What is you queston?
Your normal 177 and 20 caliber air riffles are shooting anywhere from 700-1000 feet a second and are made to kill squirrels, rabbits, etc...I would definitely not recommend try to kill a 180 pound animal with a air riffle. In fact this would be a very bad idea. More than likely the animal would die, but it may take days and even weeks, after suffering and infection set in. Don't try it.I would have to say Yes. But it depends on the air rifle and pellet. Most BB or 177 pellets will injure the animal but Pellets also come in 20 cal and 22 cal and even as large as 50 Cal. The last ones will definitely kill 180 lb animal they are the PCP type air guns (they use a scuba tank to charge the rifle and fire at about 1400 Feet per second.) Air guns are not toys and have the potential to kill. I've seen a 20 cal air pellet take down a boar. Remember a 22 cal bullet travels at 1200 feet per second. There are several air rifles that fire at that speed and above that speed, with just a pellet. Even a small pellet can kill if it hits the right spot. So the answer is YES!
Gamo Hunter Extreme 1650 FPS - Air rifle .177 Cal Air Force TalonP 900 FPS air pistol .25 Cal Hatsan AT P1 Air Pistol .177 870 FPS The Air Force TalonP is faster in .25 Cal than the Hatsan .177 Cal
Rodents
No. Just have to be old enough!