The first Hotchkiss gas operated machine gun was used by several militaries at the beginning of the 20th Century, most notably the Americans, British and the French. The American gun was used to chase Pancho Villa around in 1916-17, and in WW1 for a short time. The British and the French were more attached to the gun and it was used up till the end of WW2.
The Hotchkiss Mk.I, image from Imperial War Museum Collection
The Mk.1 was built in Enfield in .303 caliber. The Americans and the French used their own rifle calibers as well. The gun could be fired from 20 or 30 round strips, or from a belt made of shorter strips if used in vehicles. The odd stock was to accommodate the charging handle, a bit disconcerting due to the fact that when opened it occupies the space your face normally would.
Royal Navy convoy duty 1942
The Brits didn't use these guns with infantry as such, but were used in many other ways. The Royal Navy used them in escort ships, and Q ships (armed trawlers meant to suck U-Boats into a trap) in both World Wars. They were used in early tanks mainly in the Destroyer role, which were meant to smash barbed wire and keep German heads down till the infantry arrived. They were used by the Aussies and the Imperial Camel Corps in the Sinai in 1917 as they were easy to transport by horse, camel back,and early armored cars.
Picture of Royal Navy dual mount, picture by Imperial War Museum
Following video from SitsinShadow's channel
Euroarms Italia has many great guns for sale, which is killing me as they are in Italy and I'm not. One gun they've had recently, and which didn't last long, is a Ferdinand Früwirth made Shutzen rifle using the Werndl system.
All pictures on this post from Euroarms Italia
The Werndl was Austro-Hungary's first modern breech loading rifle. Up untill that time the Hapsburg Army was using trapdoor converted Lorenz muskets. The final version of the Werndl fired a small, high velocity (for the period) 11mm slug and for a time could compete with the best rifles in Europe. The shooter operated a revolving drum to load the cartridge, an 11.15 mm black powder round that by 1877 had a muzzle velocity of 1400 fps.
The Werndl system was designed by Karel Holub, who worked in Josef Werndl's factory, which eventually became Steyr Mannlicher. Früwirth's factory built many guns, and sold to certain Gendarmarie units. Werndl had apprenticed to Ferdinand Früwirth himself, and eventually took over his firm, among others.
The Werndl was not adaptable to a magazine system, but despite that had stayed in service for 20 years and later was used as a rear echelon weapon during the First World War. Shooting them now takes a bit of work. Cartridges can be made from 348 Winchester brass, but not easily, but some companies like Bertrams sometimes have cases for sale. Finding or making these cartidges, then shooting these old beasts are a very satisfying part of gun collecting.