I ran across this on the internet archive. It's free to read and/or download. It's rather informative on airguns made up until 2003. J. E. House is a good writer. He has a book on American air rifles posted there as well.
Cheers,
J~
CO2 pistols & rifles [electronic resource] : House, J. E : Free Download, Borrow, and Streaming : Internet Archive
CO2 Pistols & Rifles
archive.org
Cheers,
J~