So I can't use a regular air compressor to fill these tanks?
No-the pressures used are from 2000-4350 psi. Also any hint of petroleum oil combined with the high pressure air is potentially explosive! There are purpose made high pressure compressors for filling guns and air tanks. Dive compressors are generally best, but are very expensive. The subject of compressors is a world unto itself! Some research is called for before taking that step.
Welcome to the rabbit hole!
Upvote 0