"The gun and its development" by W.W. Greener is fascinating.
"The art of gunsmithing - the shotgun" by Lewis Potter is full of good info
and,
"Gunsmithing" by Roy F. Dunlap , whilst not specifically a shotgun book is jam packed with all kinds of handy stuff.
"The British shotgun" Vol's 1-3 by I.M. Crudgington contain a mind boggling amount of info on designs and patents
I also found Richard Arnold's book on auto's very good too.

Last edited by Nick. C; 04/14/19 07:16 PM.
Rust never sleeps !