i have a question about Bf 109s spinner cannon

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Dec 10, 2005
anyone in here know that Bf 109s late type have one 20mm or 30mm cannon.

i have been collect many Bf's picture and i noticed that the muzzle hole on spinner is different according to Bf's type :confused:

in my opinion, Bf with 20mm MG 151/20 cannon have bigger diameter on it's spinner hole than Bf with 30mm MK108 cannon.

i think it's because of MG 151/20 have long barrel.

am i right? please let me know that

For either type of cannon, the gun sits well behind the spinner. In fact it sat partially behind the engine, and completely behind the reduction gearing.

Both guns fired through a larger than gun-bore tube to reach through the spinner. The size of the hole might have varied considerably from design to design. It is quite possible that some 20mm versions had larger diameter holes than later 30mm versions, but this had nothing to do with barrel length. Probably, as the war progressed the design of the spinner became more aerodynamic and thus the size of the hole became smaller.



in fact. i was compared G-6 picture with G-10/U4 picture.

i have checked again. then i found that G-6's hole is bigger than G-10's hole. there's nothing to do with barrel length but period
Someone here should be able to post a cutaway of the 109. If they do you will see the gun is mounted well back of the spinner.


Well, that cut-away dosn't really show much of the MG151/20, but the breech is listed (i believe item 51), and it is just in front of the pilot. For the barrel to reach out the spinner, it'd have to be 15-20 feet long!


The forward mounting point for the cannon was in the same place for both 20mm and 30mm cannon. The barrel of the 151 was 550mm longer than the barrel of the 30mm. The mounting point was the inner end of the barrel.

The spinner from the F to K did not change. I would like to hear why the blast tube would be smaller for a weapon firing a shell 10mm larger. If anything it should be larger with the larger volume of propellant gasses from the 30mm. Also by going smaller, components such as the prop hub and prop reduction gear box would have to be redesigned as the blast tube ran through them.

If one wants cutaway drawings of the 109F-4 go to http://www.airwar.ru/other/draw/bf109f.html
Well this diagram is wrong I believe anyhow. Based on a book about the Bf-109 that I am reading right now the Bf-109G-14/U4 had the Mk-108 30mm Cannon and not the MG-151.
The only difference in spinner perf size is (As previously noted.) between E&F models. E models posessed this mod, in hope of a cannon never installed on this model. the reason for the size would seem to be, barrel cooling not caliber.
The internal diameter of the blast tube was 70mm, which limited the guns which could be fitted there. That accounts for the slender barrel of the MG 151 - it was intended from the start for such a mounting.

Tony Williams: Military gun and ammunition website and discussion forum

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