World's Ugliest, Lousiest 4000 psi compressor Ever Guaranteed
Using powerful airguns requires filling them up with high pressure. Really high pressure. 3000 to 4000 psi (up to 250 bar).
You have three ways of doing that:
1. The hand pump
2. A scuba diving bottle or so
3. An own compressor
While the hand pump requires a few hundred strokes to fill a rifle, the scuba bottle requires frequent visits to the dive center or gun store in order to get it refilled. The compressor is the "king's way" of course. Buuuut it is expensive. Like, 2000 € expensive.
This video shows a very cheap, very quick and very dirty hack how to make a compressor from a hand pump, a battery drill, an old moped chain and sprocket set plus some leftover wood.
It is ugly, it is messy and it creates scary noises. But it works! See for yourself.