This remarkable site covers the development of the machine-gun before the War. There is new (to me) info about familiar models and there are details of some that I haven't come across before; the Nordenfelt, de Knight, Perino, and Skoda, for example.
There's a lot on the Madsen, and it seems to solve the mystery of the Berthier MG that we couldn't track down a year or so ago. It would appear to be the Berthier-Pacha 1908, which is similar in appearance to the Madsen, as is the Kjellman.
"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.
Well spotted James. This is just part of a huge work in 5 volumes of which 4 are available (the other 3 extant are large .pdf which are quite slow-loading). The master index is
... where Volume I includes Part III as in the link you provided. The earlier parts include volley guns and manually-cranked machine guns.
Hmm... I see the Lewis can be fired from the shoulder, all you need is this handy little attachment to turn it into a sort of 'bull-pup'. And it does indeed seem to work - that appears to be a live firing in progress.
Volumes IV and V go into excruciating detail on the design and classification of these weapons:
Volume IV
PART X ANALYSIS OF SYSTEMS PART XI SCHEMATIC ILLUSTRATIONS OF REPRESENTATIVE MECHANISMS
Volume V
PART XII POWER DRIVEN CANNONS AND MACHINE GUNS PART XIII RECOIL (RECIPROCATING) OPERATED CANNONS AND MACHINE GUNS PART XIV REVOLVER CANNONS PART XV GRENADE LAUNCHER MACHINE GUNS PART XVI AMMUNITION DEVELOPMENT PART XVII RELEVANT PATENTS IN PUBLIC DOMAIN 1952-1971