The Mitrailleuse Saint Etienne Mle 1907 is one of those rare classic machine guns that was a complex mechanical nightmare prone to overheating and parts failure. Yet it saw active service in the French African colonies and, by necessity, throughout the Western Front in World War I.
The St. Etienne M1907 is an air-cooled, gas operated, strip fed heavy machine gun chambered for the French 8mm Lebel rifle cartridge. It is unique in its operational design as the gas piston is of a blow forward configuration using a rack and pinion system to operate the reciprocating parts. This complicated mechanism was the heart of the numerous inherent problems with the gun.
To fully understand how and why this design came about we must first discuss the involvement of Austrian Army Captain Baron Adolph von Odkolek with the French gun-making firm of Hotchkiss. In 1893, Odkolek invented and built a prototype of a machine gun utilizing a new system of operation based upon a gas piston system mounted beneath the barrel and a cartridge loading feed strip design. This system of tapping off a small portion of the rapidly expanding gases of a fired cartridge through a small hole in the barrel, pushing against a piston positioned directly below and parallel to the barrel driving the operating rod, is the basis of all gas operated weapons of today. Since Odkolek had no manufacturing facility, he brought his hand made prototype to the Hotchkiss Company just outside of Paris at St. Denis. It was there that Laurence Benet, chief engineer of the company, and his assistant, Henri Mercie, quickly determined that the prototype gun made by Odkolek was impractical in its physical design but recognized the value of the reciprocating gas piston system and the unique feed strip mechanism. They promptly purchased the gun and the patent rights from Odkolek and designed their own gun using these new innovative concepts without fear of infringing on the patents of Maxim and Browning.
Their newly designed gun became the Hotchkiss Model 1897 that proved to be fairly reliable but had overheating problems. There were some minor changes to the mount and cooling ring material (from brass to steel) and the new updated version, the Hotchkiss Model 1900, was purchased by the French government and used in its colonies building a fairly respectable reputation for operation and reliability.
Nevertheless, the French army wanted a machine gun of their own design. Using nationalistic pride as an impetus and, more importantly, not wishing to pay royalties to the commercial Hotchkiss company, they set about to create their own version of a “perfect machine gun.” With five years of operational experience and performance data on the Hotchkiss M1900 at their disposal, the National Arsenal at Puteaux (APX) produced in 1905 their version of a modified gas system, air cooled, strip fed machine gun.
The Puteaux M1905 had a number of unique design features. It was the first gun to utilize the blow forward method of operation. The method of gas operation in the M1905 consisted of a gas trap at the muzzle with a hollow tube in which the gas was driven back to about the middle of the barrel where it then operated the reciprocating parts of the gun. Another innovative feature was the implementation of a variable rate of fire mechanism. This device could be manually adjusted by the gunner to fire at a rate ranging from eight shots per minute to 650 shots per minute. The M1905 is visually distinctive by a series of cooling rings from breech to muzzle. Not produced in any large numbers, the Puteaux M1905 was issued to French infantry units and was probably sent to selected colonial units as well. The gun was not well received in the field and it was quickly determined that a simplified and more reliable version was needed.
The French army then tasked the St. Etienne Arsenal (MAS) to simplify the gas operating system of the Puteaux M1905 and make other improvements to the gun. They maintained the blow forward concept but simplified the gas operating system by using a gas port in the middle of the barrel to drive the gas piston and operating rod. They also eliminated all of the cooling rings on the barrel to simplify the manufacturing of the barrels. The result was the St. Etienne Model 1907 – a machine gun forever destined to be considered one of the oddest designed weapons ever put into large production, adopted by a national army and used in a major conflict.
The operational heart of the St. Etienne M1907 is the gas piston and operating rod that, instead of being driven rearward to unlock the bolt, traveled forward. This meant that since the piston and connected operating rod were traveling the wrong way, a rack and pinion gear mechanism was needed to move the bolt in the proper rearward motion. The gas piston is attached to an operating rod that attaches to the rack upon which the pinion and cams work. As the gas piston/operating rod/rack moves forward upon firing, the pinion spur gear rotates and engages a cam follower that unlocks the bolt bringing it rearward while at the same time lifting the cartridge feed tray and turning the cartridge feed sprocket. Locking of the M1907 bolt is accomplished by the cam way going over-center at the end of the forward rotation of the pinion gear cam.
The tripod for the M1907, designated Tripod Model 1907C, accommodated only the M1907 machine gun. The tripod consists of two main groupings: the support pivot head and the tripod body. The two front legs had a unique knee joint a few inches below the head that could be folded under for the purpose of lowering the tripod to enable the gunner to fire from a prone position. The rear telescoping leg has a small seat affixed to it as was common to tripods of that era. A revised tripod was produced, the Model 1907 Omnibus (multi-purpose) that had a modified support pivot head to allow the mounting of the Puteaux M1905, St. Etienne M1907 and Hotchkiss M1900 machine guns.
In 1916, further modifications were made to the M1907 machine gun and the new designation was M1907T. (T for Transformé, or transformed or, in simple English, “modified.”) These changes and/or modifications included the addition of a large ring gas regulator, front sight heat compensating mechanism, changing the rear sight from a leaf sight to a drum sight and modification to the feed sprocket gear to accommodate the use of a cloth belt. At this time the older M1907s were supposed to be returned to the Chatellerault Arsenal (MAC) for upgrading to the M1907T specifications and examples today of an unmodified M1907 are exceptionally rare. Both St. Etienne and Chatellerault arsenals manufactured the M1907 and M1907T with St. Etienne being the primary manufacturer. Chatellerault manufactured a total of 11,105 guns in which 9,661 were manufactured during the war years of August 1914 through November 1918. The St. Etienne Arsenal produced over 30,000 guns. Total production between the two arsenals reached a high point of over 1,900 guns a month. It is interesting to note that each arsenal used its own serial number system beginning with number 1 for each year. Thus, in the example of the gun featured in this article, serial number 7522 dated 1916 at the St. Etienne arsenal means that it was the 7,522 gun made in 1916, not the 7,522 gun ever made. Additionally, the actual number could be repeated but with a different date and the number could also be repeated by a different manufacturer. It should also be noted, to confuse the issue even more, that the year corresponded to the year in which the production order was received and not necessarily the year when the gun was actually manufactured. Also, the “T” designation was not used on identification markings on the guns but could be externally determined visually by the use of the large gas ring regulator, front and rear sight changes.
The M1907T gas system had a large regulator around the barrel at the gas port. By turning the regulator, different sized gas port openings were presented to allow altering the rate of fire by speeding up or slowing down the movement of the piston by restricting or increasing the volume of gas allowed into the gas expansion chamber. Since the gas port tended to eventually foul with carbon deposits, the larger hole settings were generally used.
One benefit of the gas piston and the bolt moving in opposite directions is that the gun actually fired quite smoothly since the recoiling energies tended to counteract each other.
The variable rate of fire mechanism used on the Puteaux M1905 was also employed on the M1907 and M1907T. A hydraulic system dashpot was located inside the rear of the receiver box directly below the trigger mechanism. A push/pull engaging switch and a setting wheel located on the outside left rear bottom corner of the receiver box allowed a choice of rate of fire ranging from 8 shots per minute to 600 rounds per minute. When pushed in the dashpot is engaged and when pulled out the dashpot is disengaged. The setting wheel was turned to determine the actual rate of fire desired by the gunner.
Another interesting feature of the M1907T is the front sight heat compensation mechanism. The front sight is attached to the barrel casing in a spring loaded vertical slide and not to the barrel proper. Because the barrel casing got hot during firing, the front sight would heat up as well but at a different rate and temperature resulting in a different and changing point of aim. To counter this, a steel rod ran along the length of the top of the barrel casing and connected to a lever system that was attached to the front sight post. As the steel rod expanded, it pushed the levers that in turn pushed the front sight post down against the spring allowing everything to remain “on target” as the gun heated up. The tangent rear drum sight is calibrated up to 2,400 meters but is adjustable only for elevation with no provision for windage.
The large steel main spring under the barrel housing had to be left exposed to help facilitate cooling of the spring. Otherwise, it would get so hot it would loose its temper and thus its recoiling ability or just break altogether. This exposed spring invited all sorts of reliability problems due to dirt, mud and the elements interfering with its movement. The right receiver access door and the locking bar shutter door on the left side of the receiver were also a source of problems for the introduction of foreign material. And the eleven large cooling slots along the bottom of the receiver box also invited foreign material introduction problems.