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Why is there such a significant rearward blast from the 30mm cannon?


Braeden108

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High rate of fire, probably with the breech closed and locked for close to  the bare minimum of time needed to stop the cartridge case splitting. No wonder there's plenty of hot gas venting from the ejection ports.

 

NJWob9L - Imgur.jpg


Edited by jym
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5 hours ago, WinterH said:

As far as I know, GSh-30-2K is not a revolver cannon. It has two barrels with one chamber each, recoil from one charges the other, but breeches themselves are pretty well sealed I think.  From a cursory look online, comparing muzzle velocities and lengths of GSh-30-2K seems to support this because they have almost the same length and muzzle velocity, and 2A42 isn't a  revolver cannon either. As far as I know no current Russian autocannon use revolver cannon design.

You're absolutely right, i thought it was a revolver design as well..

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2 hours ago, jym said:

High rate of fire, probably with the breech closed and locked for close to  the bare minimum of time needed to stop the cartridge case splitting. No wonder there's plenty of hot gas venting from the ejection ports.

 

NJWob9L - Imgur.jpg

 

This image shows the Gast principle but the Gsh-30-2 is gas operated and not recoil operated so it works a little differently than this. The attached image gives a hint of the internals

E083E770-871B-4EED-BB69-50CCFFFF19A3.jpeg

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so when one barrel fires the gas piston pushes the bolt backwards to eject the spent cartridge, and the pivot and crossbar in the center moves the other bolt forwards with a new shell to fire? this then repeats. 


Edited by tempusmurphy
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8 hours ago, Weta43 said:

There's a photo with part of the receiver mechanism removed showing the internals further up the page

The picture you posted before is a Gsh-23L. That gun is recoil operated. The Gsh-30-2 has a different mechanism

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16 hours ago, tempusmurphy said:

so when one barrel fires the gas piston pushes the bolt backwards to eject the spent cartridge, and the pivot and crossbar in the center moves the other bolt forwards with a new shell to fire? this then repeats. 

 

From what I can gather from the image I posted this roughly the mechanism. Only that the gas piston pushes the teethed bar backwards. This then turns the big cogwheel in the center and moves bar on the other side in the reverse direction. These teethed bars are connected to the bolts I would assume.

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4 hours ago, tempusmurphy said:

I would think at the high rates of fire this cannon can do, the strain and wear on the cog/toothed gear mechanism would be high to say the least 😄

Indeed 😄 that’s why these parts are so massive

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On 5/29/2021 at 6:09 PM, Kerberos said:

The picture you posted before is a Gsh-23L. That gun is recoil operated. The Gsh-30-2 has a different mechanism

"

The Gryazev-Shipunov GSh-30-2 (ГШ-30-2) or GSh-2-30 is a Soviet dual-barrel autocannon developed for use on certain ground attack military aircraft and helicopters.

The cannon is not related to the Gryazev-Shipunov GSh-30-1, but is a recoil-operated cannon using the Gast principle, like the Gryazev-Shipunov GSh-23L.

"

Cheers.

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1 hour ago, Weta43 said:

"

The Gryazev-Shipunov GSh-30-2 (ГШ-30-2) or GSh-2-30 is a Soviet dual-barrel autocannon developed for use on certain ground attack military aircraft and helicopters.

The cannon is not related to the Gryazev-Shipunov GSh-30-1, but is a recoil-operated cannon using the Gast principle, like the Gryazev-Shipunov GSh-23L.

"

I don't know how GSh-23L and GSh-30-2 exactly work, or if they really differ. However, principle can be the same, but the mechanism may differ, at least theoretically. Gast principle is, as far as I know, using energy from one barrel's firing to cycle the other, but the cycling itself may perhaps be achieved in different ways: gas piston, long recoil, short recoil etc.

 

They are both Gast guns, yes, this is already well established.

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6 hours ago, Weta43 said:

"

The Gryazev-Shipunov GSh-30-2 (ГШ-30-2) or GSh-2-30 is a Soviet dual-barrel autocannon developed for use on certain ground attack military aircraft and helicopters.

The cannon is not related to the Gryazev-Shipunov GSh-30-1, but is a recoil-operated cannon using the Gast principle, like the Gryazev-Shipunov GSh-23L.

"

That is a mistake on Wikipedia. Other sources say that it is gas operated and you can clearly see the gas pistons in the picture I posted.

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Some remarks:

- flash seen on camera can be also attributed to the synchronization of the framerate of the camera to the firing cycles. If you take frames in between shots, you do not record muzzle flash at its peak, while gases flow from the breach might be more constant due to accumulation through the cover

Also those might not be just gases from the breech but also from the gas system - depends where are venting points. But they seem to be below the cover

Flash hinders at muzzles can also help if they are of the right design. I read about design that was compatible with even very old night-vision (very sensitive to strong outer light sources) sets as it caused sort of "stall" effect. Just to explain - that flash hinder was mounted either on LMG or some AR that was equipped with the night vision

- GSh-23 and GSh-30-2 both use boxing system. According to the book by man (from former Czechoslovakia) that was involved in design of the automatic weapons and was teaching the subject at university, 23mm version has breeches connected by lever and sort of the crossed gas system - gases from firing barrel accelerates its own breech rearward but they are channeled behind opposing piston and accelerate it forward - and vice versa.

GSh-30-2 uses some cogwheel system to link the breeches and classic gas system for each barrel.

Both have fixed barrels. Breech parts are guided by specific grooves that accelerates them through the leverage and slows them down when necessary thus reducing the impulses from recoil (i.e. when breech is hard-stopped from full speed by some bumper, MG-42 works that way)

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