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I was thinking of using the Danuvia (Gebauer) 12.7mm GKM 40M as the basis for future armament but cant find the specs of this weapon. RA do you have anything on it? ( the Italians bought a license during WW2)
Specs for the Gebauer are difficult to find. The only ones I have found are a weight of 42kg and 2600rpm rate of fire. It isn't clear which weapon they are for though, the 8x57 or 12.7x81 version. If you have a look back through Italian news you'll see a few versions being used experimentally by Italy, including one upscaled to 13.2x99. Eventually a choice between revolver cannon or chaingun?
The Rpm seems to high for the 12.7mm, it was supposedy three times higher than the Breda-SAFAT so ~1,500-1600rpm
Originally posted by Vukovlad
The Rpm seems to high for the 12.7mm, it was supposedy three times higher than the Breda-SAFAT so ~1,500-1600rpm
The problem is also that theres no information whether the rate of fire is for one barrel or both. If its for both then the performance is quite poor as the conventional gas operated Gebauer in 7.92mm fires at 2000rpm. Btw, 750 x 3 = 2250rpm not 1500-1600rpm.
Since the GKM is always synchronized I assumed that they compared it to the synchronized Br-S 550-575rpm
This post has been edited 1 times, last edit by "Vukovlad" (Jul 28th 2008, 8:31pm)
Originally posted by Vukovlad
Since the GKM is always synchronized I assumed that they compared it to the synchronized Br-S 550-575rpm
Its a big assumption to make given the lack of data. For a 12.7mm weapon, 1000rpm is easily possible by this time. The FN-Browning gave 1050rpm when chambered for the 13.2x99 instead of 12.7x99 with a few changes. The UB is around the same in 12.7x108. An M3 Browning boosting rate of fire to 1200rpm is definitely possible at the time, but would interfere with production. You've also got the Molins Hispano 20mm at 1000rpm. The Gebauer system means that the only thing effecting performance is the pressure drop in the barrel and the mechanical limits. A greater rate of fire should be possible which could correspond to 1600 or 2200rpm. Its difficult to tell.
So lets make an even bigger assumption, the Gebauer 20mm Motordriven Automatic Cannon
Weight: 50-55kg
ROF: 700rpm/barrel
Caliber: 20x110 (or to have real fun the Swedish 20x145)
The question is also how much power it drains from the engine
The question is also how much power it drains from the engine
My impression is not much. The quick calculations I did indicate around 1hp at most but I'm really sure if they're any good. All that the motor needs to do is move the breech block backwards and forwards.
For weights I'd add around 20-30kg on top of the weights of the basic guns themselves to cover the clutch, gears and shafts. For a version in 20x110 i'd imagine around 130-150kg total with 900-1000rpm per barrel at least. The 20x145R round isn't loaded particularly hotly. You don't gain much in return for a much larger case.
So something like this
Total weight: 140Kg
ROF: 950rpm/barrel
Caliber: 20x110
I am surprised by your remark about the 20x145, it was after all introduced mid war as an AA/AT gun ammo
In Tony William's data tables
here you've got details. Compared to the 20x110, it fires a slightly heavier shell at lower velocity.
Interesting most AT rifle rounds seem to have a lower velocity than the HS, due to tungsten core?
Originally posted by Vukovlad
Interesting most AT rifle rounds seem to have a lower velocity than the HS, due to tungsten core?
It depends on the penetration mechanism used. The actual rifle calibre types have a much higher velocity because they use a different mechanism. More tomorrow when I have time...
Another reason for the velocity difference is that there are limits to how much muzzle energy you want in a rifle that's going to be fired from the shoulder, limits that don't apply to weapons intended to be mounted in a vehicle or on a carriage. The Lahti and the S-18/1000 series fired 20mm x 138B rounds that had a higher muzzle velocity, but they were also loaded in weapons that pushed the outer edge of being anti-tank "rifles".
Quoted
Originally posted by Vukovlad
Friday, April 26th 2024, 7:01pm
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