Bf 109 G-6/U4 and the MK 108

[Nick Beale]

Following on from the earlier thread, I recently found something in deciphered material that may be useful. The file is National Archives HW5/464 and the document is CX/MSS/T 147/39.

On 31 March 1944, 7. Jagddivision ordered that "In view of the present shortage of 3 cm ammunition MK 108, the units must help each other out. ZG 76 is to surrender to (Roman) I./JG 5 1000 rounds. The units will arrange for handing over between themselves."

British Intelligence added this note: "An order for setting up a Sturmstaffel on 20/11 stated that the MK 108 in the Me 109 had not been very successful (T 9/53). Other mentions of this weapon in e.g. T 19/82 (Test unit 25 Achmer fitting it obliquely in Me 110) and R 66 (B) 26 (to be adapted to engine DB 605 A 1)."

So there were problems with the MK108/Bf 109 combination.

P.S. I have not looked at any of the earlier messages that the analysts mention and will not have the chance for some time.

[George Hopp]

There were also problems with the MK 108/Bf 110 combination. "Oblt. Rudolf Thun, NJG 5, observed, 'The MK 108 was disliked by most experienced crews. First, the muzzle flash was much too blinding for effective use at night, and second, the gun spring would not contain the pieces in case of a shell exploding in the barrel.' The second part of this complaint was echoed in the GWF memo of July, 12, 1944, which noted that continued fighter unit criticisms made necessary a strengthening of the MK 108's feed chutes, of the breech-block slide tubes and springs, and of the slide tube support plate." from Monogram Close-Up 18 "Bf 110G."

Nick, would you happen to have a date for your T 19/82 (Test unit 25 Achmer fitting it [MK 108] obliquely in Me 110) as we have a famous shot of such an installation in the 110 being shown to foreign airmen (Mankau, page 230), and it would be nice to get an appoximate date for the photo. Incidently, a single MK 108 was supposed to be used as an oblique weapon in the 110H. Some references say two, but there would not have been enough room for 2 MK 108s and their ammunition in the confined space behind the rear gunner.

Thanks for that info, Nick.
George

[Juha]

Hello George
Being at work I cannot check from my copy of Mankau's book but IIRC in the photo there are Finnish Air Force officers looking into the cabin of a Bf 110G with oblique cannon. If so the time is summer 1944 when a group of Finnish pilots were taking part in night fighter training in Germany.

Juha

[Nick Beale]

Originally Posted by George Hopp

Nick, would you happen to have a date for your T 19/82 (Test unit 25 Achmer fitting it [MK 108] obliquely in Me 110) George

No, but here's how you do it … AFAIK, in the numbering of this "CX/MSS/" series of documents T = teleprint and R = report; 19 = the day it was deciphered (not the day it was sent); 82 means it was the 82nd teleprint issued by Bletchley Park that day.

OK, so CX/MSS/T 147/39 which I quoted was issued on 7 April 1944. If 7 April was "day 147" then you can count back to find what date "day 19" was. That will get you to within about 1 - 5 days of the date of origin of the message.

The date of decipherment tells you which file to search in: the NA catalogue them by those dates (the spines of the files themselves tell you the message numbers they cover as well but the catalogue doesn't).

[George Hopp]

Thank you both for that excellent information.
So, if I read you correctly, Nick, the message would have been sent April 7 - 19 = ca. 19 Mar 44. Thanks again.
All the best,
George

[Nick Beale]

Originally Posted by George Hopp

Thank you both for that excellent information.
So, if I read you correctly, Nick, the message would have been sent April 7 - 19 = ca. 19 Mar 44. Thanks again.
All the best,
George

Sorry George, what you need if 7 April was "day 147" is to count back 128 days to find "day 19" - something I was too lazy to attempt! (But I do know 1944 was a Leap Year!)

[Juha]

Hello George
I checked from my copy of Mankau's book and yes we are talking on same picture. And what more the same photo is published in Suomen Ilmailuhistoriallinen Lehti 1/2004 and according to that publication in the photo Oberleutnant Werner Rapp is showing a Bf 110 G-4 of NJG 5 to Finnish officers on May 12 1944. The Finns were not pilots in the night fighter training but from an earlier group which was sent beforehand in May 44 to Germany to a fact-finding mission on German night fighting systems and equipment.

HTH
Juha

[yogybär]

Originally Posted by Nick Beale

[...]British Intelligence added this note: "An order for setting up a Sturmstaffel on 20/11 stated that the MK 108 in the Me 109 had not been very successful (T 9/53). Other mentions of this weapon in e.g. T 19/82 (Test unit 25 Achmer fitting it obliquely in Me 110) and R 66 (B) 26 (to be adapted to engine DB 605 A 1)."

So there were problems with the MK108/Bf 109 combination.
[...]

The original topic of this thread is much more interesting...

Does anyone have information on problems with the MK108 in the Bf109?

It was prone to jamming if shot at g-loads, at least until early 1945 iirc. Anything more?

PS: Does anyone have information on how big the percentage of MK108-equipped Bf109 were in 1944/45? We had a discussion at butch2k's forum on that, but that one was purely for production figures of Bf109G-6/U-4, G-10&14/U-4. There we had a rough percentag of 30 iirc.

[George Hopp]

I could give you the stuff they found during testing the 1st 30 machines. How many of these problems were fixed, I don't know.

I do know that the stength of the breech block spring and its supporting structure was a problem well into 1944 (as I mentioned above).

[olefebvre]

Not only did the mounting caused a problem but the shells as well, the type "C" shell had troubles, not exploding on impact when hitting within certain angles and/or velocities.