Synchronized machineguns?

Here’s some wiki info with pics and drawings.

Some further information from Flying Guns – World War 1: Development of Aircraft Guns, Ammunition and Installations 1914-32, which has a whole section on synchronisation:

The problems described above were largely solved in WW2 by the use of constant-speed propellers. However, the rate of fire was, on average, still reduced by between 10% and 40%, with around 25% being typical. A key point is that MGs modified for synchronisation were no longer automatic, but were fired semi-automatically by the synch system.

[quote=“Falcon”]I have read that originally the solution the French used was armour plating the leading edges of propellers to deflect bullets, which was not always effective.

Apparently Austria-Hungary used an electrical system for their interrupter mechanism, as they were ahead of anyone else in terms of electrical technology during WW1.[/quote]

Thats true, I don’t think it was just the French either that tried it. It was the Germans who first got it right with intercepted machine guns. Whether they invented the process I’m not entirely sure but they were quick to capitalise on it and by 1916 dominated the air .
You have to understand the massive combat superiority that a pair of front mounted machine guns directly within the pilots line of sight gave compared to a top mounted Lewis gun.

Another extract from Flying Guns:

[quote]The first design for a device to synchronise the firing of the gun or guns with the rotation of the propeller was patented by the ingenious Franz Schneider [a Swiss engineer], of whom we have already heard (although Blériot was also working in this field). However, his first patent in July 1913 was more precisely an interrupter rather than a synchronising gear; i.e., the mechanism prevented the gun from firing while a propeller blade was in front, instead of positively firing it when the line was clear. This latter approach was the method eventually adopted, although the term “interrupter gear” remained in popular but inaccurate use thereafter.

It should be noted that a synchronising gear effectively turned the machine gun into a semi-automatic weapon, as it only fired one shot for each firing impulse received. It seems that Schneider had thought of this method as well, so should not be denied the credit. His patent envisaged a flexible synchronised gun, albeit with a limited range of movement.

This was followed in April 1914 by the Frenchman Raymond Saulnier’s patent mechanism which used an oscillating rod to fire the gun (a flexible link was also proposed). More significantly, Saulnier also built the first practical synchronising gear at this time, but suffered from applying this to a Hotchkiss which was inherently unsuitable for synchronisation. Obviously discouraged by the results, Saulnier invented the steel deflector wedges as a simpler solution.
The Edwards brothers patented a synchronisation gear in Britain in the summer of 1914, but when they approached the RFC with it, they were told that the service did not have any money for that kind of development.

The first use of synchronising gear in aerial warfare did not occur until 1915, following the capture by the Germans in April of that year of a French aircraft using the deflector type of mechanism. The Idflieg (Inspektion der Fliegertruppen) sought a comparable system and Anthony Fokker (who, although Dutch, had a factory in Schwerin, Germany) produced the first example of an aircraft fitted with a synchronising gear in May 1915. It seems likely that the Gestänge-Steuerung gear was actually designed by Heinrich Lübbe, an employee of Fokker’s, based on Saulnier’s patent. Initial versions used rigid connecting push rods to fire the gun but these proved troublesome (they were sensitive to temperature changes and would contract in the cold, preventing operation of the trigger) so flexible drive shafts were employed in later designs.

It was the Germans who first got it right with intercepted machine guns. Whether they invented the process I’m not entirely sure but they were quick to capitalise on it and by 1916 dominated the air .

Correct, it was Fokker in 1915 which used a 1913 patent from Schneider.

Correct, it was Fokker in 1915 which used a 1913 patent from Schneider.[/quote]

Well, what can I say… thanks for the quote! ;)

Never too late to give credit to engaged researchers :)

I resurrected this old thread because I recently came across some photos online that may show an important event in the development of synchronized guns in U.S. during WW1.

The following photographs are from the San Diego Air and Space Museum Archive photograph collection ( … 091826122/ ) and are available for noncommercial use. I think these photos may be the photographic record for a synchronized MG test conducted here in the US on December 27th, 1917. The test is briefly discussed in The Machine Gun, Aircraft and Air-Borne Weapons; Vol. 1, Part IV, Chinn, G. M. 1951; page 321:

“An informal test was held on 27 December 1917, at which time another type of hydraulic synchronizing gear, also manufactured by the Marlin-Rockwell Corp. and similar to the Constantinesco gear, was tried out at rates varying from 200 to 600 rounds per minute with a total angle of dispersion of 63°. It was the closest and most accurate synchronization accomplished in this country with any type of machine gun so far. The Marlin aircraft machine gun has the distinction of being the first gas-operated weapon to be synchronized successfully.”

Below are some of the photos from the series (all 18 photos can be viewed on line) which show the demonstration firing of a Marlin Aircraft Machine Gun, Model 1917, Cal. 30 and a Browning Aircraft Machine Gun.

Clicking on each photo will take you to photobucket where you can open a larger image using the magnifier (with a “+” symbol) in the upper right corner of the image.

The photos are shown with my interpretations:

Photo #1- A general view of the event showing the Marlin MG in place on the mockup aircraft and the audience consisting of representatives from the various branches of the military, press, technicians etc.

Photo #2- Another view of the audience. You can see the mock wooden prop (in vertical position) and round sheet metal witness disc, near the center of the phote. Note the gentleman to the extreme left, I believe that is John M. Browning.

Photo #3- View from behind the cockpit showing the Marlin gun in place

Photo #4- The engine is running, U.S. Army officer in the cockpit, 2 officer are standing on a platform facing the camera, note the cloth MG belt to the right of the fellow crouched down just behind the engine compartment. At the rear of the Marlin MG you can see attachments with tubing running down (to the aircraft engine), that is part of the synchronizer mechanism which worked via hydrolics off of the running aircraft engine.

Photo #5- The synchronized Marlin MG is being fired through the spinning propeller arc and into the witness disc.

Photo #6- This clearly shows the bullet holes in the sheet metal witness disc after a test firing; at the 1:00 position on the disc you can see a tight string of bullet holes.

Photo #7- Checking out the results of the Marlin MG test firing by U.S. Army and Navy representatives.

Photo #8 & #9- The Browning MG in place. Photo #9 is an enlargement which shows the tell tale barrel shroud of the Browning MG.

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Photo #10- Browning MG after test firing.

Photo #11- Photo of the synchronizer from the firing demonstration.

My carton for Cal. 30 Tracer Cartridges Model 1917 Aircraft Use Only is just one example of the multitude of specialized ammunition produced at Frankford Arsenal and else where during WW1 for synchronized guns:

Any additions or corrections are welcome.


With my limited knowledge of cartridges, was unaware machine guns were synchronized with aircraft propellers. Very neat.

Thank you for posting these great photos Brian! The cartridge box is very nice too!!!


Brian: A very interesting series of photographs, and thank you for posting them. The engine is a Hispano Suiza; the partial airframe is a dark mystery to me. Jack

Read somewhere John Browning did participate in those synchronization tests. The engine by the is a Hispano Suiza better known then as a Hisso. My father was the ordnance chief of the 68th fighter squadron in the Pacific from Guadalcanal on up the islands. Our P-39 and P-40 had synchronized guns using hydraulic synchronizers. The synchronizers only worked properly within a certain engine RPM range. Dad said several pilots came back with holed and dinged propellers because they fired outside that RPM range.

The Germans had in WW1 a label „ Nur für Flieger” (for air plains only)


In WW2 a additional label was inside the 1500 round box.



Individual boxes are sealed in cellophane.



Does the box you have contain any contents? A note that came with mine says it contained 136 rounds of FA 32.


British Box 288 ctn, is Hirwaun (HN) repacked Canadian DAC44 Aircraft quality ball (No difference from Land use Ball by 44) in “Infantry” 32 rd CTNs For Royal Hellenic Army (Greek Civil War, 44-48).

Red Print about “not to be used after 46” is the typical Two Year Time limit on “aircraft” Ball. In any case, this ammo would not have been used in anything but Greek Army training, as it is Cartoned…Greek (British Cwth) Combat ammo was sent either Belted (Vickers), Boxed (48rds) for Bren and Aircraft use, or Clipped in 50 rd. Bandoleers); ammo for Aircraft would have been Pre- steel link belted in UK.
Have seen all these Packaging varieties Here in Australia and at Dillons (Arizona)…except for the Metal link belt from Greece. ( HS of 44-50s Greek Used Ammo include R^L, GB,K, etc; DAC,DI Z; MF, MG, MH, MJ, MW; U & U<>; Mostly in 48 rnd Packs for the Cth.Nations, 32 and Bandos and Belts for the British, and Mostly repacked/checked by Hirwaun ROF in Wales.

Crates also inspected at 5 year intervals in Greece, and “test” ammo samples removed replaced by HXP (Greek Powder Co) New .303 cartridges. Greek inspection stamp is Green and of course, in Greek.

Doc AV

Hi Joe,

I got my box empty but 1932 should be correct.
Cal. 30M1 lot 1605 was the last lot of M1 ammo delivered in 1932 ( delivered on Dec 27, 1932)


Wow neat! Being not only a young cartridge collector, but also a young pilot this is fascinating! Thank you all for your information!