13,2x99 Hotchkiss history

So im new on this forum and im fairly new to the ammunition history scene. For the last years ive done a lot of research about swedish military aircrafts and their armament. Since a lot of it is swedish has made finding info fairly easy for me as i live in Sweden. But when i got to the 13,2 mm automatkanon m/39 (13,2 mm FN m.1939) i stepped right into a wall. Not only is there a general lack of info on this weapon (or was until i made a wikipedia page dedicated to it) but there is a general lack of info on its ammunition, the 13,2x99 mm Hotchkiss. When doing research on it i found that a there was a lot of threads about it in this forum. Considering that there should be a lot of people here who knows the general history of this round and where it was produced and sold i thought why not create a thread about it.
So my knowledge is lacking a lot about this subject. As ive understood, the 13,2x99 was developed about the same time as the 13,2x96 Hotchkiss and it was mainly used for export? It was produced in a lot of countries and mainly used for anti air guns? The FN herstal company was the first ones to make a gun for it that was meant to be mounted on airplanes? That gun became the FN m.1939 and was only used in Sweden and romania? Ammunition during ww2 was only produced in Sweden and Italy? And thats about it.
I hope this thread can explain a lot of the mystery’s about this cartridge.

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During WW2 Germany also made this ammunition (steel cased with a special HE proj. design) for likely French and Belgian guns they had captured.

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The 13.2 x 99 cartridge was designed in the 1920s by Hotchkiss for their heavy machine gun which was used in the AA role, most extensively by the Japanese Navy who called it the 13mm Type 93. The Italians made their own gun to fire this ammo, the Breda M31, and mounted it in a light armoured vehicle. FN made a version of the .50 Browning MG under licence in both aircraft (air-cooled) and AA (water-cooled) variants: the customer could choose between 12.7mm and 13.2mm calibre. Except for the small difference in calibre, the round was identical to the 12.7 x 99 (.50 BMG) so the two are easily confused. To reduce the chance of this, the case was later shortened by Hotchkiss to 96mm. During WW2, Germany modified the case again by shortening it to 93mm so it could take cannon-type explosive projectiles made for the MG 131.

Yes, I believe you are right that the FN 13.2mm Browning aircraft gun only saw service in Sweden and Romania, although the Japanese Navy also copied the big Browning aircraft gun, choosing the 13.2mm calibre they already had in service; this was known as the 13mm Type 3.

It’s worth remembering that before WW2 the 13.2x99 cartridge was far more common than the 12.7x99, being in service in many countries in three different types of gun; at this time, the .50 BMG was largely confined to the USA. WW2 changed all of that, and postwar the 13.2mm Brownings were mainly converted to 12.7x99 - it only needed a barrel swap.

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We also may remember about Polish production here.

Tony, the projectile used in the 13.2 was not the MG131 type. As you remember the MG131 used a separate driving band while the 13.2 had a unique design where the steel body of the projectile formed a thicker portion and engaged the rifling with the bare steel body. This actually could be the reason why the Germans had no (known) AP types in this caliber.

Left the 13mm MG131, right the 13.2mm Hotchkiss:
Zwischenablage

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Anyone have any data for the ap round btw? All the data i have is the velocity which is 820 m/s

Tony, the projectile used in the 13.2 was not the MG131 type. As you remember the MG131 used a separate driving band while the 13.2 had a unique design where the steel body of the projectile formed a thicker portion and engaged the rifling with the bare steel body. This actually could be the reason why the Germans had no (known) AP types in this caliber.

Thanks for that correction! I should have checked the 13.2x93 HE in my collection more carefully…

Also some swedish data i have says that the ap projectile had 12 mm pen on a 60 degree slope at 200 m

Romania also produced this cartridge:

Did they actually produce it? I thought they only had a handfull of 13,2 mm FN m.1939 guns which where replaced rather quikcly with the mg151.

Alex, Do you have any data on the German Hotchkiss loading - projectile weight and MV? Also, what designation was it given?

Some years ago I received a message from a Frenchman concerning a rather different history of the 13.2 mm Hotchkiss (apologies, I did not note his name). The message was as follows:

First of all, I want to specify that there is no relation between a. 50 BWG [presumably BMG] and a 13.2 x 99 Hotchkiss ctg case! The first Hotchkiss researches for a heavy machine gun ctg started early 1901 in relation with S.F.M. and the original ctg was more likely a scaled up 7.92 than any American one. Main improvements were carried out after WWI with the adoption of a variation of the 13 mm Tankgewehr ball. The final tests were ended early 1925.

Why two case length ?

After the adoption by the french Navy of the 13.2x99 mle 1930, once noticed that barrels had a too short life . A competition between the three ammunition factories in charge of the production started ; each studying the possible improvements. It was Cartoucherie de Valence, Manufacture du Haut Rhin and Société Française des Munitions. A detailed report of each improvement of the three factories will be out of subject and very long but one was effectively a better improvement. Its specificity was the adoption of a large groove in the medium, cylindric part of the ball. But , due to the position of the groove, it was for reasons of manufacture impossible to crimp easily the case neck. The only solution was to shorten the case neck and crimp it in the upper part of the ball groove. The case lengh was then shortened of 3 mm, the new cartridge was adopted as 13.2x96 mle 1935. Groove and short case are concomitant.
Note that the two ctg length can be used in the same barrels and that the two case length continued to be manufactured in the different manufactures, even after 1935.
The reduction of the case length is for manufacture reasons and NOT a question of distinction with the .50BWG case. In the 1930’s , the Hotchkiss 13.2 had a world wide extension than the .50 BWG and could be used in Hotchkiss MG , Air cool and water cool Browning MG , Breda and Scotti MG , Japanese Hotchkiss MG.

I did not take this very seriously when I received it, but wondered if there could be anything in it…?

In case it came from Philippe Mention I would consider it to be most serious data as he is digging French archives up and down for the 13.2mm Hotchkiss project.

Tony, I do not have the manual for the German 13.2mm ammo and also do not know anybody who does.
This is one of the few manuals we are missing for some unknown reason.

This includes the manuals for the German:
13.2mm Hotchkiss
2.8cm s.PzB. 41 (28/20mm squeeze bore)
37x250R C/36 (M42)
37x252R Flak DA ®
128mm KwK
800mm Dora
And sure some others.

Not Philippe, I know him!

I wouldn’t have thought that anything that size would be lost very easily!

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The German Bundeswehr hast lost tanks and aircraft in their inventories. So what is a manual in wartime?

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Oops - this is where I need an emoticon with a very red face…I contacted Philippe, and he told me that he had indeed sent me the original information I posted above!

This is fascinating, since it shines a completely different light on the history of this round. Philippe tells me that he has accumulated a great deal of information on the round which he may be posting on his aferhm.org website in due course.

Ok here is the 13.2+99 and 96 they both seem to be the same yet they are not the
difference is in the necks.There is supposed to be a variation in case lenght but there
seems to be little 99,24 to 99,08mm.they would be difficult to differentiate if it would not be for the
neck.they are both incendiary tracers and the bullets are different too,one is cupro nickel
the other seems to be copper washed steel.
Sherryl

Hi Sherryl,

The cartridge shown in photos 3 and 4 is a 12.7x99mm (.50BMG) AP from the Dominican Republic.

Brian