Bf 109 Prototype/Limited Production Armament

Hey guys, I just registered and this is my first post. I had a question about a late version Bf 109 Kurfurst model that maybe somebody could help me with. I've read from several sources that a certain number of the 109 K-4 models were equipped with MG 151 15mm auto cannon in place of the standard production issue MG 131 heavy machine guns in the engine cowling. I don't know if it was only one that was made, a few, a small production run, or it was offered as a mod kit out in the field - if it existed at all. I had heard that one squadron received a small number of K-4's with this configuration, and that it may have also included the engine mounted Mk 103 instead of the Mk 108. The 15mm 151's were said to have been partially visible and exposed outside the cowling due to the difference in size. I saw that this subject came up back in 2004 and I was wondering if anyone from that time, like Emil Kurfurst, was still here? I was looking for this info partly because I also play War Thunder (I fly German planes almost exclusively) and I would love to petition Gaijin to make this particular armament available to the K-4, if one of these existed and flew. There has to be a documented case and for that model to have flown in order to qualify for inclusion in War Thunder. Anyone familiar with Gaijin of course will know that they downplay Germany's history as much as possible (and play up Russian technology to a level bordering on absurd) so the chance of them including a configuration like this in the game is about one in ten million, but I'd like to try anyway, if there's a historical basis.

Welcome to the forums!

The Bf109K-4 did have several armament variations, but I haven't heard of the MG151/15 being used on any of the K series types (K-6 prototype or the rare K-14).
Keep in mind that the MG151 was a large weapon and there simply wasn't enough room in the cowling for two cannon.
The MK103 and MK108 were substituted with a MG151/20 for the motorkannone location, as there was enough room for it.

The MG151 was almost six feet long and weighed almost 100 pounds, unlike the MG131, which was less than four feet long and weighed about 37 pounds.

And don't be surprised about Gaijin's bias, Oleg Maddox pulled the same thing with the IL-2: Sturmovic series. When an I-16 can catch an Fw190A-8 in level flight, well, you know.

What Dave said.
I'd add that the stipulated armament featuring the two MG 151s under the cowl was 1st mentioned in one of the books from the 1960s IIRC. When the MK 103 was to be installed on the Bf 109K-8, even the compact MG 131s & their 13mm ammo boxes were deleted to make space for the big honking cannon and it's ammo.

Cowl MG 151 in the Bf 109K is an old old myth

GrauGeist said:

Welcome to the forums!

The Bf109K-4 did have several armament variations, but I haven't heard of the MG151/15 being used on any of the K series types (K-6 prototype or the rare K-14).
Keep in mind that the MG151 was a large weapon and there simply wasn't enough room in the cowling for two cannon.
The MK103 and MK108 were substituted with a MG151/20 for the motorkannone location, as there was enough room for it.

The MG151 was almost six feet long and weighed almost 100 pounds, unlike the MG131, which was less than four feet long and weighed about 37 pounds.

And don't be surprised about Gaijin's bias, Oleg Maddox pulled the same thing with the IL-2: Sturmovic series. When an I-16 can catch an Fw190A-8 in level flight, well, you know.

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That's an amazing amount of difference between the two guns - 63lbs! That's almost as much as both 131's put together. So 200lbs for both, which is 126lbs of extra weight, not counting the difference in ammo. And then there's the extra considerations for other new equipment - directional gear, bigger engines, etc. if this would have worked even with the new DBM605 G-51 engine. They did manage to cram the 131's into the cowling on the G10 so I thought they might have been able to work something for the 151's, but that' s an extra two feet - I didn't realize there was that much of a difference. There was a major change in maneuverability from the G2 to the G6 just from switch from the MG17 (which needed to happen, but still) so I can't imagine how that much additional weight would have affected performance. Maybe if they got smaller pilots? They could have recruited a special squadron of short people to fly this particular model lol. Thanks for the response and the warm welcome

tomo pauk said:

What Dave said.
I'd add that the stipulated armament featuring the two MG 151s under the cowl was 1st mentioned in one of the books from the 1960s IIRC. When the MK 103 was to be installed on the Bf 109K-8, even the compact MG 131s & their 13mm ammo boxes were deleted to make space for the big honking cannon and it's ammo.

Click to expand...

I think one of the sources was a book by Messerschmitt. It seemed like there might be something to it, and considering how many weapons concepts had been tried. The 103 was huge! I can see them having to remove everything else to make room. I know the 108 is a potato launcher, but at least you get a lot of bang for the space they take up.

Denniss said:

Cowl MG 151 in the Bf 109K is an old old myth

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It does make me wonder why they didn't redesign the wing like Supermarine did, and carry more of the extra firepower there. I mean a lot of other fighters carried a much greater load of weaponry and still managed to perform well. I know the 109 was designed to be as light as possible so maybe the unanticipated increase in aircraft firepower was a bigger problem for how it was originally intended. Meaning it would have needed a more in depth retooling and they put the focus on jet/rocket aircraft instead.

The MK 103 was too big to fit into the 109. A slimmed-down version was developed (designated MK 103M) and this was squeezed into one 109K-10 for trials, but it was unsuccessful (not sure in what way) and was never installed for combat.

They did some modifications for weapons during the Bf109's lifetime, like the "buell" cowling of the Bf109G, when the MG131 was installed in place of the MG17 (which was about the same length as the MG131, but about 10 pounds lighter) - this itself shows how little room was available in the 109's engine bay.

A.G. Williams said:

The MK 103 was too big to fit into the 109. A slimmed-down version was developed (designated MK 103M) and this was squeezed into one 109K-10 for trials, but it was unsuccessful (not sure in what way) and was never installed for combat.

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It was a probably small thing of ww2 ending that busted the project
The MK 103M was probably what the Ta 152C and Do 335 would've been carried as motorkanone.

I don't know the reason for the MK 103M being considered a failure. I think it was Schliephake or Hahn who wrote about it.

A.G. Williams said:

I don't know the reason for the MK 103M being considered a failure. I think it was Schliephake or Hahn who wrote about it.

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In the Schliephake's book, I can find only the trials of MK 103M aboard the Ta 152 in role of tank busting, date 21st May 1944. Noted good things are the closeness of the weapon to the sight, retained maneuverability and speed vs. the case when lighter/smaller weapon is installed in the Vee, and rigidness of the installation - all as stark contrast to the Fw 190A that was also tested together with Ta 152 for that task. Shortcomings were that Ta 152 was powered by a liquid cooled engine, and, a shortcoming shared with the Fw 190A installation, that ammo required tungsten and required a shot on a vital part of a tank and under 300 m so it can do the damage. No other shortcomings of the Ta 152 installation were mentioned.
Surprisingly, the Fw 190 installation was recommended for further testing, while the Ta 152 with MK 103M was rejected; again, this is for tank busting purposes per this test.