Water cooled British Vickers machine gun. Approx 500 rounds per minute. The gun could be broken down into two pieces for transport.
British motorized machine gun battery near the Somme.
Water cooled German Maxim machine gun. Same rpm as Vickers. This weapon accounted for 90% of the British casualties on the opening day of the Somme Offensive, 1-Jul-1916.
German Machineengewehr 08 (Maxim). Designed by American Hiram Maxim and manufactured in Spandau, Germany. The Germans had 12,500 of these killers in 1914 as compared to the several hundred Vickers of the British army. The Germans would produce over 100,000 Maxims during the war.

Heavy Machine Guns
TypeCaliberFeedWeight (lbs)CoolingRounds/min
German Maxim MG 087.9mmbelt41/sledmount 83water600
German Maxim MG 08/157.92mmbelt33/bipod 3water600
British Vickers Mk I.303inbelt35/tripod 52water500
French 1914 Hotchkiss8mmstrip52/tripod 65air600
Austrian Schwarzlose8mmbelt44/tripod 44water400
Russian 1910 Maxim Sokolov7.62mmbelt41/mount w/armour 121water500-600
American Colt.30inbelt36/tripod 56air400-500
American 1917 Browning.30inbelt33/tripod 53water450-600
First weight is gun weight followed by accessory type and weight. Thanks to Robert Segel for these numbers.

Light Machine Guns
TypeCaliberWeight (lbs)FeedRounds/min
German 1915 Muskete7.92mm21.75magazine450
German Bergmann7.92mm30belt600
German MG 08/187.92mm32belt600
French Chauchat (CSRG)8mm20magazine250
American Chauchat.30in20magazine250
American BAR M1918.30in19.5magazine500