If you're interested in aircraft guns, you will want to know about "Rapid Fire - The Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces."
This includes data on, and illustrations of, all of the WW2 aircraft guns of 12.7-57mm calibre, together with information about what they were fitted to and why different air forces made different armament choices.
It also includes data on all large-calibre automatic guns and ammunition from WW1 to the present day, plus information on AA gun effectiveness of navy and army equipment.
Details are on my military gun and ammunition website (plus links to amazon.com reviews):
http://www.users.globalnet.co.uk/~autogun/ You might also find something of interest in the military gun and ammunition discussion group:
http://www.delphi.com/autogun/messages/ Tony Williams
