What does a 177 caliber air rifle shoot?

It depends on the air rifle. All 177 air pistols and rifles fire 177 ammo. Some will fire, only pellets. Some can only fire, BB's. But, some can shoot both. And. Brake barrel air weapons can fire, special darts. But, DON'T, fire darts through a rifled barrel. You can do it but it can damage it. Only through a smooth bore barrel. When in doubt, check with the maker of YOUR gun.