Did the German 3,7 cm Flak SK C/36 exist?

[Tony Williams]

I am currently researching the history of automatic cannon and their ammunition and would appreciate some help with an obscure German naval AA gun: the 3,7 cm Flak SK C/36. I have put down my thoughts on this almost unknown project as follows:

The evidence in favour of its existence is as follows:

1. 37 x 248R cartridge cases do survive, headstamped C/36.

2. No other gun used this cartridge except for the Flak M42, which raises the question: why did the Flak M42 use this round instead of the standard 37 x 263B of the other Flak guns of this calibre, unless it was already in existence for an earlier gun?

3. An informal drawing of the gun exists, in Skwiot's book on German naval guns of WW2.

4. A C/36 mounting was initially used for the Flak M42 (which emerged in 1943). What was that first used for, if not the C/36 gun?

However:

1. I have been unable to find any photos or descriptions of the SK C/36; only the drawing in Skwiot mentioned above (but the gun is not referred to in the text). One problem in identification is the great similarity to the M42 (judging by the drawing), which could make them hard to tell apart.

2. A highly detailed German study of the 3,7 cm Flak M42, which lays out the development path for the gun in some detail, makes no mention of the C/36 gun, only the mounting (Waffen Revue, issues 106 and 107).

Conclusion (provisional):

On the face of it, the C/36 was a mid/late 1930s attempt to produce an automatic naval AA gun which was probably built in small numbers (enough to be worth establishing a production line for the unique ammunition) but not followed through. The M42 looks remarkably similar, both guns having a strong resemblance to the Bofors gun family, with a vertical clip ammunition feed, a long-recoil mechanism, and a boxy receiver. So perhaps the M42 was just a refinement of the C/36.

There is also a very close resemblance to the Soviet 37 mm M1939, which was developed very rapidly over a few months in 1938 after a 45 mm version was abandoned as being too big and heavy. The M1939 is normally described as being based on the Bofors 25 mm, but scaling-up that design would have required a lot of development work in a very short space of time.

Given the close technical cooperation which existed in the late 1930s between Germany and the USSR, and the fact that while the ammunition for the C/36 and M1939 is not identical it is almost exactly the same size, it would seem not unreasonable to suggest that the C/36 played some part in the development of the M1939 and subsequently the M42. However, I have so far been unable to find any solid evidence for the existence of the gun.

Can anyone help, and provide more information about the C/36 (assuming it existed?)

 

[starviking]

Can anyone help, and provide more information about the C/36 (assuming it existed?)

I’m a naval fan, but really don’t know much about the Kriegsmarine, however, for ships I am interested in I can access a lot of information on data and equipment - might be an idea to repost this in the Naval section too - I’m sure we have a fair few KM fans who may have info on odd mountings.

 

[Grey Havoc]

Presumably this was a Rheinmetall design.

 

[Tony Williams]

Can anyone help, and provide more information about the C/36 (assuming it existed?)

I’m a naval fan, but really don’t know much about the Kriegsmarine, however, for ships I am interested in I can access a lot of information on data and equipment - might be an idea to repost this in the Naval section too - I’m sure we have a fair few KM fans who may have info on odd mountings.

Thanks for this, will do.

 

[Tony Williams]

Presumably this was a Rheinmetall design.

Technically - although it bore a very close resemblance to a Bofors gun and was presumably strongly influenced by it. The mechanism (as well as the ammunition) appears to be quite different from that of the contemporary Flak 18/36/37, also from Rheinmetall.

 

[Wurger]

Tony, I recall having something about it, with possibly illustrations. Give me a few days and I will check it out.

 

[Tony Williams]

Excellent! Thank you very much.

The only illustration of the gun I have seen is this one:

 

[Wurger]

My source has this illustration as well. I reckon there is another one, with a different mount. I`ll check.

 

[stimpy75]

i found these but the m42 uses the same 37mmx 264 round
Sry the source is Enzyklopädie Deutscher Waffen from Terry Grander

 

[Tony Williams]

Thanks for posting, but that source is incorrect in saying that the M42 used the same ammunition as the Luftwaffe Flak guns. No surprise, it is a very common - and much copied - mistake. Only ammo anoraks like me are sufficiently interested to know!

The guns pictured in your source are all the Luftwaffe type. Some of these guns were mounted on ships, but that was never planned. Only with the M43 did the Navy mountings use the same guns and ammo as the others.

 

[stimpy75]

thx for the clarification, i am currently digging some of my books and i also asked my nephew to check the library in cologne which has many rather older books from the 60-70s to check for me
here is another pic of a naval version but not the one you want

 

[Tony Williams]

Yes, the C30 was manually loaded.

The photo looks a bit odd - I've never seen a pic of the C30 with a flash-hider before. This gives lots of photos: https://commons.wikimedia.org/wiki/Category:3.7_cm_SK_C/30

 

[Jemiba]

In the Waffen Revue, N° 106, III. quarter 1997, the C/36 is mentioned and shown, but as AA gun mount only.
But the photos show a strong similarity to that in Tonys post :

 

[Tony Williams]

In the Waffen Revue, N° 106, III. quarter 1997, the C/36 is mentioned and shown, but as AA gun mount only.
But the photos show a strong similarity to that in Tonys post :

Thanks, good pics.

One thing is for certain: the gun is either an M42 (which initially did appear on the C/36 mounting, but not for long) or an SK C/36 which of course appeared with the C/36 mounting. I do not have enough clear illustrations of both types of gun to decide which it is, because they are so similar.

It is clear that identification can be hazardous in such circumstances, with the gun and mounting designations liable to be confused.

 

[Wurger]

From "Leichte und Mittlere Artillerie auf Deutschen Kriegsschiffen", by Stehr and Breyer (Marine-Arsenal Sonderheft 18). The text adds nothing to this question and the caption states it`s a FlaK M 42 in a FlaK-Laffete M 42.

 

[Tony Williams]

This was posted on another forum - it's from "Handbuch für Admiralstabsoffiziere".

Note on the bottom right the vessels the C/36 was mounted on.

 

[Wurger]

Interesting to notice that, according this document, the 3,7cm SK C/36 was to be triaxially stabilised, in a C/36 "lafette", (not depicted in any of the illustrations published before), and using the cartridge (the weight is the same) as the "land" 3,7 cm Flak 18, 36/37 and 43 (ceiling is also the same). This does not correspond to the naval Flak 42, which fired a lighter case with a slightly higher ceiling (100m). In my opinion it is a "navalised" Flak 36, just like the one at post #11, in a hitherto unseen stabilised mount (Rheinmetall had several proposed mounts in the late 30`s, some triaxial). Posts #7, #13 and #15 represent Flak 42. Just to add another image of the C/96, in the same mount as in post #7, here it goes, taken from the Zeiss Archives: http://www.archive.zeiss.de/vimg.FA...4&qpos=2633&ipos=1&erg=M&hst=1&rpos=faust.jpg

 

[Tony Williams]

Interesting to notice that, according this document,

Which document?

There is confusion in most documents that I have seen about the relationship between the Flak SK C/36, the Flak M42, the Flak 36 (land-based but some fitted to ships) and their ammunition.

A key point is that I have been told by German cartridge collectors that 37 x 250R cartridge cases (the same as used by the M42) exist, headstamped "C/36". That is pretty definite.

My view of all of this (unless someone comes up with hard evidence to prove me wrong) is that the SK C/36 was based on the Bofors 40 mm and 25 mm guns, and used the rimmed 37 x 250R ammunition. The M42 seems to have been closely based on the SK C/36 and fired the same ammunition. I would love to find a document describing the changes made to the C/36 to turn it into the M42, but I'm not optimistic... The Flak 36 guns designed for army and air force use, and also sometimes fitted to ships, used 37 x 264B ammo, as did the multi-service Flak M43 (which bore no relationship to the Flak M42).

 

[Wurger]

Interesting to notice that, according this document,

Which document?

There is confusion in most documents that I have seen about the relationship between the Flak SK C/36, the Flak M42, the Flak 36 (land-based but some fitted to ships) and their ammunition.

A key point is that I have been told by German cartridge collectors that 37 x 250R cartridge cases (the same as used by the M42) exist, headstamped "C/36". That is pretty definite.

My view of all of this (unless someone comes up with hard evidence to prove me wrong) is that the SK C/36 was based on the Bofors 40 mm and 25 mm guns, and used the rimmed 37 x 250R ammunition. The M42 seems to have been closely based on the SK C/36 and fired the same ammunition. I would love to find a document describing the changes made to the C/36 to turn it into the M42, but I'm not optimistic... The Flak 36 guns designed for army and air force use, and also sometimes fitted to ships, used 37 x 264B ammo, as did the multi-service Flak M43 (which bore no relationship to the Flak M42).

I meant the document you have posted before my last entry. My source (Gander/Chamberlain) states the M42 as using the 37 x 264 cartridge, and that matches the data in the aforementioned table.

 

[Tony Williams]

My source (Gander/Chamberlain) states the M42 as using the 37 x 264 cartridge, and that matches the data in the aforementioned table.

Which merely makes both sources wrong... No great surprise, few authors check the sources for everything they include, they just copy from existing texts. Some errors get perpetuated in book after book. Ammunition is a specialist subject which most technical military historians know little about.

I can assure you, with 100% certainty, that the M42 did not use the 37 x 264B ammo.

Below, you can see a photo of a round of 37 x 264B ammo in my collection. Below that, you can see a photo of a disassembled 37 x 250R for the M42. Look at the bases of the two rounds - the M42 has a simple rim, the 37 x 264B has a complex belted design.
Third one down is a page from Waffen-Revue 107, giving technical data on the M42, and finally a close-up of the ammo pic in that document. You can see that the M42 used the ammo with the simple rim, not the belted case.

 

[Wurger]

Ok, I have that same source, and they look quite different designs all right! Back to the 3,7 cm SK C/36, the "Handbuch für Admiralstabsoffiziere" shows it to have the same velocity and cartridge weight as the Flak C/36.

 

[Tony Williams]

Ok, I have that same source, and they look quite different designs all right! Back to the 3,7 cm SK C/36, the "Handbuch für Admiralstabsoffiziere" shows it to have the same velocity and cartridge weight as the Flak C/36.

I have checked my references and the two cartridges had very similar performance. The projectiles were the same, and the muzzle velocities were very close. This is surprising because the Flak 36 round looks bigger so should have had room for more propellant, but on the other hand, its barrel is shorter.

 

[Wurger]

Sticking to the "Handbuch für Admiralstabsoffiziere", my best guess is that the triaxial 3,7 cm Flak L. C/36 mount was never mounted in the intend receivers (aviso Hela, fishery protection boats, torpedo boats, Type I , IX and XII U-boats, Elbe, Weser) and, by memory, most of them having just the older C/30 double mount (besides the never built Type XII). About the gun, again, in my opinion it is already depicted in posts #7 and #17, being a naval Flak 36. This is as far as my knowledge and guessing goes.

 

[Wurger]

Just to add to the confusion, this drawing shows a Flak 42 lookalike with the feeding guides set at the extreme gun rear, with no case deflector. Taken from "Leichte und Mittlere Artillerie auf Deutschen Kriegsschiffen", by Stehr and Breyer (Marine-Arsenal Sonderheft 18). Never mind the caption.

 

[Regg]

Constanca, Rumania.

 

[dandragos]

My source has this illustration as well. I reckon there is another one, with a different mount. I`ll check.

 

[Tony Williams]

That is clearly not the C/36 or M 42, as it has side-feeding of ammo rather than top-feeding.

 

[dandragos]

Still, an interesting piece. Could it be an Army Flak 36, as John Campbell says: „The Army Flak 36 was occasionally to be found in some smaller vessels. This resembled the Flak M42, with a shorter 57 cal barrrel and fired same ammunition”?

 

[_Sarcasticat_]

Still, an interesting piece. Could it be an Army Flak 36, as John Campbell says: „The Army Flak 36 was occasionally to be found in some smaller vessels. This resembled the Flak M42, with a shorter 57 cal barrrel and fired same ammunition”?

Yes the Flak 36 and Flak 43 both saw service onboard various ships in the KM. For instance, Ftb 1939 T-35 was equipped with 2x1 3.7cm/57 M43's/Flak 43's.

 

[dandragos]

Still, an interesting piece. Could it be an Army Flak 36, as John Campbell says: „The Army Flak 36 was occasionally to be found in some smaller vessels. This resembled the Flak M42, with a shorter 57 cal barrrel and fired same ammunition”?

Yes the Flak 36 and Flak 43 both saw service onboard various ships in the KM. For instance, Ftb 1939 T-35 was equipped with 2x1 3.7cm/57 M43's/Flak 43's.

Thank you! I was also curious about the mount. Is it the C/34, as mentioned above?

 

[_Sarcasticat_]

Still, an interesting piece. Could it be an Army Flak 36, as John Campbell says: „The Army Flak 36 was occasionally to be found in some smaller vessels. This resembled the Flak M42, with a shorter 57 cal barrrel and fired same ammunition”?

Yes the Flak 36 and Flak 43 both saw service onboard various ships in the KM. For instance, Ftb 1939 T-35 was equipped with 2x1 3.7cm/57 M43's/Flak 43's.

Thank you! I was also curious about the mount. Is it the C/34, as mentioned above?

Based on the shape of the shield, they were just Heer mounts.

 

[dandragos]

Still, an interesting piece. Could it be an Army Flak 36, as John Campbell says: „The Army Flak 36 was occasionally to be found in some smaller vessels. This resembled the Flak M42, with a shorter 57 cal barrrel and fired same ammunition”?

Yes the Flak 36 and Flak 43 both saw service onboard various ships in the KM. For instance, Ftb 1939 T-35 was equipped with 2x1 3.7cm/57 M43's/Flak 43's.

Thank you! I was also curious about the mount. Is it the C/34, as mentioned above?

Based on the shape of the shield, they were just Heer mounts.

The one in the picture i posted resembles the one in post nr. 17.

 

[Regg]

That is clearly not the C/36 or M 42, as it has side-feeding of ammo rather than top-feeding.

I believe that this is a "marine" Flak 18/36.
This model is in the Naval Museum in Constanta. It was installed on Romanian ships.
In addition, he was on some ships of the Greek fleet: Averoff, Vasilefs Georgios I, Vasilissa Olga.

 

[Regg]

Still, an interesting piece. Could it be an Army Flak 36, as John Campbell says: „The Army Flak....”?

Yes the Flak 36 and Flak 43 both saw service onboard various ships in the KM. For instance, Ftb 1939 T-35 was equipped with 2x1 3.7cm/57 M43's/Flak 43's.

Are there photos?

 

[Regg]

Similar anti-aircraft guns on Romanian ships. Poor quality photos...

 

[_Sarcasticat_]

Still, an interesting piece. Could it be an Army Flak 36, as John Campbell says: „The Army Flak....”?

Yes the Flak 36 and Flak 43 both saw service onboard various ships in the KM. For instance, Ftb 1939 T-35 was equipped with 2x1 3.7cm/57 M43's/Flak 43's.

Are there photos?

You can see the mounts and guns of USS T-35 (DD-935) online. They aren't clear-cut, but they're clear enough.

 

[Tony Williams]

I believe that this is a "marine" Flak 18/36.
This model is in the Naval Museum in Constanta. It was installed on Romanian ships.

Somewhere in the archives must be an explanation for why the German navy did not simply adopt the army Flak 36 on a marine mounting instead of developing their own Flak C/36 (and the later M 42) using their own unique ammo.

 

[Regg]

Flak 18 vs Flak 36

 

[Tony Williams]

From my forthcoming book Autocannon:

3,7CM FLAK 18, 36, 37; M36; BK
3,7: 37 × 264B AMMUNITION.

This series formed the bulk of the Luftwaffe’s medium-calibre automatic AA guns for the duration of World War II. The prototype of this series was designated the Rheinmetall ST 10, which was nominally handed over to Solothurn for further development as the S10-100, before being formally returned to Rheinmetall-Borsig. The mechanism used a short-recoil rotating-head lock with the cocking handle, attached to the front of the bolt, riding in a long slot in the receiver, which curved sharply as it approached the forward end of its movement, rotating the bolt head locking lugs.

The guns in this series were basically the same, with L/57 barrels, weighing 278–295kg and firing at 160rpm. The differences between the Flak 18, 36 and 37 mainly involving the mountings and sights: the Flak 18 had a cumbersome four-wheel mounting and was only made in small numbers, from around 1935, before being replaced by the Flak 36 which had a much improved two- wheel mounting. The Flak 37 differed in being fitted with a new sight, the Flakvisier 37, which incorporated a computer with a clockwork drive. Mounting weight in action varied from 1,550 to 1,750kg.

The BK 3,7cm was adapted to be carried by aircraft, primarily in the anti-tank role.

 

[Tony Williams]

A further extract from Autocannon:

3,7CM FLAK SK C/36:
37 × 250R AMMUNITION.

This almost unknown gun was the Kriegsmarine’s first attempt to acquire an automatic 37mm AA cannon. Instead of using the 37 × 264B Flak ammunition (as used in the Flak 18, Flak 36, Flak 37 and Flak M43), Rheinmetall-Borsig designed the gun around a version of the Army 37mm cartridge used in manually-loaded tank and anti-tank guns. This rimmed cartridge case was modified by giving it a thicker rim, presumably to strengthen it in view of the more violent extraction forces in an automatic mechanism. The HE shells it fired were the same as those used in the Flak 18+ ammunition.

The gun bore a close resemblance to the Bofors guns, including the boxy receiver and a gravity feed above the mechanism taking 5-round clips, and was presumably based on these. It was fitted to a C/36 single mounting. Few technical details are available, beyond a gun weight of 240kg (930–1,040kg including the three-axis mounting) and a rate of fire of up to 180rpm.

It seems that not many C/36 were made, being deployed on only a few vessels, according to a Handbuch für Admiralstabsoffiziere which lists the Aviso Hela, the two Type 1A submarines U-25 and U-26 (and possibly some Type IX), torpedo boats and fishing protection vessels.

The Kriegsmarine had another try some years later, resulting in the 3,7cm M42 (see below) which used the same ammunition and general design, retaining the boxy receiver and the vertical gravity feed. It is evident that the M42 was an improved SK C/36, and the first mount- ing used by the M42 was the C/36.

Confusion over the German 37mm naval AA guns and their designations is widespread, and not only over whether the C/36 term is being used to describe the gun or the mounting (if the latter, the gun could be either the SK C/36 or the M42, as they are hard to tell apart). Also, it is often stated that the SK C/36 is nothing more than a marine version of the Luftwaffe’s Flak 36, when the two guns are completely different in their design as well as in the ammunition they fired. The situation is even more confused as some Flak 18/36/37 guns were indeed fitted to ships as a quick way of boosting their AA defences, so alertness is necessary in determining which guns are actually being referred to.