It's stickied you fucking imbecile.
Recently came across this, it's the complete 5-volume set of "The Machine Gun" by George M. Chinn (1951)
>The Machine Gun. History, Evolution, and Development of Manual, Automatic, and Airborne Repeating Weapons Bureau of Ordnance Department of the Navy, Washington, 1951 (Vol. I-V)
It's about 3000 pages of history and design info, as well as lots of the calculations.
http://www.milsurps.com/content.php?r=347-The-Machine-Gun-%28by-George-M.-Chinn%29