Wow Michael, most impressive. What can you tell me about German and Commonwealth MGs used in 1914?
The most obvious change was with Germany. The use of the MG 34 and later MG 42 in replacing WW I guns in all roles. The Germans used the Maxim MG 08 as the standard medium/heavy MG in WW I and introduced a lightened version as a "LMG" as the MG 08/15. The "light" version was still water cooled and heavy. They also had small numbers of Madsen and Bergmann MG 15 LMGs which were true LMGs. Some MG 08 were still in use in WW II. Use the Axis Minor MMG/HMG for the MG 08 and an Axis Minor LMG with 3 pp for the MG 08/15.
Austria-Hungary used the Schwarzlose MG M 07/12 as the MMG/HMG and was still in use by many armies (Dutch, Hungarian) in WW2. The Axis Minor MMG/HMG is the closest. It was one of the few non-Maxim type MMG/HMG used in WW I.
Britain used the Vickers-Maxim in WW I and until the '60s. The Russians used their version of the Maxim from WW I until about the '60s.
The Italians used the Fiat-Revelli M 1914 fed by a magazine holding 10 5 round rifle clips, later developed into the belt fed M 1935 WW II MG.
The Hotchkiss M1914 was used by the French and Japanese in both WW as their MMG/HMG. It was also used by the US in WW1 alongside the Browning M1917 (US HMG). The British also used the Hotchkiss M1909 in their armoured cars and tanks.
So far, apart from the Germans, MMG/HMG in WW I use were still in use in WW2. The main difference was with LMG. By WW2 many nations were using using versions of either the WW I Madsen or the inter war Czech ZB 26 (e.g. Bren). The Soviets had their DP 1928, the French the FM 24/29 and the US only a few Lewis and Johnson M1941.
In WW I the significant LMGs were the Madsen, Lewis and Chauchat.
The Lewis was used by Belgium, Britain, Russia and Germany (captured). Still in second line use by many nations in WW II. A bit heavier and bulkier than their competitors. Axis Minor LMG, but 2 PP .
The Danish Madsen was used by Germany and Russia in WW I and by many nations until WW II (Denmark, Norway, Dutch). Allied Minor LMG.
The Chauchat was used by the French and US. Use Italian LMG with B10 for French use and B9 for US use.
The US had the BAR in both WW but is not a separate weapon in ASL.
I will not comment much about Italian or Japanese MGs in either WW except to say that many used oiled rounds (add dust and mud), weird feeding mechanisms and multiple calibres. The Japanese in particular had such a variety of weapons, mechanisms, 2 calibres (6.5 & 7.7 mm) and even rimmed and non-rimmed 7.7 mm rounds! One MG, if I remember correctly, had to have a lower power 7.7 mm than the standard rifle round due to reliability issues.