3,7 cm Flak SK C/36

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Tony Williams
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3,7 cm Flak SK C/36

Post by Tony Williams » 30 Apr 2020 14:09

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 as follows:

Was there a 3,7 cm Flak SK C/36?

The evidence in its favour 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, 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?)
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Sturm78
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Re: 3,7 cm Flak SK C/36

Post by Sturm78 » 01 May 2020 13:02

Hi Tony,

I have these two images of different German weapons in 3.7cm caliber but unlucky I don`t have information...

I've always wondered why it took the Germans so long time to develop / deploy a really effective medium caliber automatic anti-aircraft weapon... :roll:

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Tony Williams
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Re: 3,7 cm Flak SK C/36

Post by Tony Williams » 01 May 2020 18:13

Thanks for your response Sturm78, the drawing is the one in Skwiot I mentioned. I see whoever added the caption covered both possibilities!

I should add that the SK C/36 and the M42 were entirely different from the other German 3,7 cm Flak guns (the Flak 18/36/37); the Flak M43 was different again, despite them all being made by Rheinmetall.
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Sturm78
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Re: 3,7 cm Flak SK C/36

Post by Sturm78 » 17 May 2020 18:00

Hi Tony,

Another image from AHF

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Tony Williams
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Re: 3,7 cm Flak SK C/36

Post by Tony Williams » 17 May 2020 18:33

Thanks - but the caption says it was the SK C/30, which was the manually-loaded naval Flak gun firing 37 x 380R ammunition. On the other hand, the gun in this picture has a conical flash hider on the muzzle, which the C/30 generally did not (although I have seen one picture of a C/30 fitted with one). Withe back end of the gun covered up, it's difficult to see what it was.
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Sturm78
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Re: 3,7 cm Flak SK C/36

Post by Sturm78 » 17 May 2020 20:22

Hi Tony,

The caption is wrong. I think it is tha same gun model of my first image

Sturm78

Tony D.
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Re: 3,7 cm Flak SK C/36

Post by Tony D. » 18 May 2020 00:08

[quote="Tony Williams" post_id=2269087 time=1589736818 user_id=7870]
Thanks - but the caption says it was the SK C/30, which was the manually-loaded naval Flak gun firing 37 x 380R ammunition. On the other hand, the gun in this picture has a conical flash hider on the muzzle, which the C/30 generally did not (although I have seen one picture of a C/30 fitted with one). Withe back end of the gun covered up, it's difficult to see what it was.
[/quote]

Tony W.,

Both the elevation arc and the spokeless handwheels in Sturm78's photos look identical to the photo you sent me earlier. Until you sent me your photo, I had never seen a C/30 with a flash hider. If you look closely at the flash hider in Sturm78's first photo, note that it is perforated very similarly to yours. I believe that both photos that Sturm78 posted appear to be of the same gun/mounting as yours is.

So, perhaps this is not a C/30?

----------------------------------------------------------
Edit:

You say:
[quote]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.[/quote]

The Flak 36 and 37 are described in Skwiot's book on page 305. From the sketches, these are the land (Wehrmacht) versions, with the caption for the C/37 saying "A naval weapon was derived from this model." So, I think that there was a land version of the 3.7 cm C/36 & 37 and then a naval version was introduced but this was based upon the C/37, not the C/36. The differences were in the sighting mechanism, and the C/36 appears to have been discontinued once the C/37 entered production (my surmise from the text in Skwiot and Hogg).

Checking Hogg's "German Artillery of World War Two", pages 150-152 show similar photos and sketches. Hogg notes (page 152) that the shell design was altered in 1940 from a dual band to a single band in an effort to save copper and that the barrels were altered to have a shorter chamber (thus a longer rifling length) to accommodate this change. Barrels with the short chamber were stamped with a "V" (verkurzt - "shortened"). I don't know if this would affect the casing used. You say that it is stamped C/36, is the date visible as well? Hogg doesn't say that this happened, but perhaps the casing was shortened as well in order to save brass?


Tony D.

Tony Williams
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Re: 3,7 cm Flak SK C/36

Post by Tony Williams » 18 May 2020 09:08

OK, a few points here. First of all, the naval 3,7 cm SK C/36 and M42 (which seems to have been an improved version of the SK C/36) were completely different from the land-based 3,7 cm Flak 18/36/37. They fired different ammunition, the gun mechanism was different, the appearance was markedly different. Why, I don't know, as all of these guns were made by Rheinmetall-Borsig, so it seems odd that they didn't just put the land-based guns on naval mountings and save themselves a lot of bother (this was done to some degree later, as a war emergency measure).

The SK C/36 and M42 were very obviously based on the Bofors guns, with a boxy receiver and an ammunition gravity feed on top of the gun (the land-based Flak guns fed from the side). There was of course a lot of technical collaboration between Germany and Sweden in the 1930s (and also exchanges of equipment and data between Germany and the USSR, plus Sweden and the USSR - the Soviet 37mm M1939 AA gun was another Bofors copy.

The three type of 37 mm ammunition used by the SK C/36, the Flak 18/36/36 and the Soviet M1939 were all of similar size and power but definitely not interchangeable (I would post a comparative photo but there doesn't seem to be a way of uploading a pic from my file without first uploading it to the web, which is too much trouble). One other curious aspect of the SK C/36 ammo is that it is almost identical to the ammo for the German Army's manually-loaded 3,7 cm Pak gun: the only difference in dimensions is that the SK round has a thicker rim than the Pak's, presumably to withstand the more violent extraction forces of an automatic weapon.

No doubt there was, in a file somewhere at some time, an explanation for why the Kriegsmarine wanted a different 37mm automatic gun from the Luftwaffe's Flak arm, firing different ammo based on the Pak gun's. The Rheinmetall archives have very little to say about this, so it may remain a mystery.
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Tony Williams
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Re: 3,7 cm Flak SK C/36

Post by Tony Williams » 18 May 2020 09:30

Tony D. wrote:
18 May 2020 00:08
The Flak 36 and 37 are described in Skwiot's book on page 305. From the sketches, these are the land (Wehrmacht) versions, with the caption for the C/37 saying "A naval weapon was derived from this model." So, I think that there was a land version of the 3.7 cm C/36 & 37 and then a naval version was introduced but this was based upon the C/37, not the C/36. The differences were in the sighting mechanism, and the C/36 appears to have been discontinued once the C/37 entered production (my surmise from the text in Skwiot and Hogg).
I think that this is misleading: yes, during the war the navy did fit some of the land-based Flak 18/36/37 guns to ships on suitable mountings but this has nothing to do with the SK C/36 - the weapons were completely different. Take a look at the photos in Skwiot of the land-based Flak in the top-left corner of page 306 and note the slender, tubular gun body with the side-mounted ammo tray, and compare it with the pictures of the M42 in pages 338 and 339 - the SK C/36 was pretty well identical in appearance to the M42.
Checking Hogg's "German Artillery of World War Two", pages 150-152 show similar photos and sketches. Hogg notes (page 152) that the shell design was altered in 1940 from a dual band to a single band in an effort to save copper and that the barrels were altered to have a shorter chamber (thus a longer rifling length) to accommodate this change. Barrels with the short chamber were stamped with a "V" (verkurzt - "shortened"). I don't know if this would affect the casing used. You say that it is stamped C/36, is the date visible as well? Hogg doesn't say that this happened, but perhaps the casing was shortened as well in order to save brass?
No, this didn't affect the case length, and in any case the cases were different: the Flak 18/36/37 (which all used exactly the same guns and ammo, but the Flak 36 used a different mounting and the Flak 37 had different sights) all used 37 x 264B belted cases, the SK C/36 and M42 used 37 x 250R rimmed cases.
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Re: 3,7 cm Flak SK C/36

Post by Thoddy » 25 May 2020 13:12

3,7 cm Flak.jpg
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Tony Williams
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Re: 3,7 cm Flak SK C/36

Post by Tony Williams » 26 May 2020 08:13

Thanks again!
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