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#141 Marek Tucan

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Posted 30 September 2013 - 0019 AM

The 37mm on a MiG was generally a heavy bomber killer. Later variants of MiG 17 switched from 1x37mm and 2x23mm to 3x23mm (before going whole hog with missiles).



#142 Marek Tucan

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Posted 30 September 2013 - 0102 AM

By the way re. armament, a question about the Spitifres: The "C" type wing (Universal) allowed mounting 4x20mm Hispano while keeping gun bays for 4x.303 in the outer wing. Was a combination of 4x20mm and 4x.303 ever used or was it in practice strictly exclusive (ie either 4x20 or 2x20 + 4x.303)?



#143 Tony Williams

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Posted 30 September 2013 - 0207 AM

About the 'ideal armament' or so, i'd think that the 'fire power' counted as only 'destructive power' is plain wrog.

DK Tanker is right about the 12.7 mm, it was a good compromise. Not quite like the 4x20 mm HS 404, but still good enough.

I mean, the early (?) HS 404 were not really reliable, and the 60 drum magazine was too small (60 rds= 6 ''). You shoot 3x2'' bursts and you'll empty it, even if the gun is not jammed. The Spitfire Mk V, after six seconds, got its firepower cutted by 80% or so!

With the later HS 404 the situation was better and the magazine was belt-feed. Yet, the RPM with 4x20 mm was just 2,400 rpm, while the 6x50'' arrangement reached over 4,000.

About the 20 vs 12.7, of couse, it's also a matter of models. The MG FF was a 20 mm, but shall we consider it as 'better' than the Browning 0.50''? Even if the weight was the same or less, i'd say not really! I'd like more a 2x12.7 mm with 200-300 rds each!

So, i am basically for this rule: every weapon class is 'double' than the smaller one: 1x30 mm = 2x 20 mm = 4x 12.7 mm = 8x 7.7 mm. I know it's debatable, but yet, it is important to add a 'correction' that gives some detail vs the pure 'brute firepower' ratings. i.e. i would consider the 20 mm as 2-3x better than the 12.7 just if an analogous time of fire is assured (i.e. 20 seconds each?).

Don't forget, so often the Zeros used their 7.7 mm as the main armament vs fighters, and much seldom the 20 mm. You have some weapons with 30-40 seconds of fire, and some others, more powerful, just with 6-7 seconds. So, pratically, you have a big IF about the weaponry effectiveness. If you are not a good marksman, then you'll lost almos all your firepower without results. And later, try to shot down a FW 190 with just 4x7,7 mm!

Finns, as example, often replaced the HS 404 with a BERESIN (12.7 mm), and you couldn't say it was a good deal, unless you start to think about the ammunition an reliabily.

Ammos, weight and reliability (also vs frost, vibrations, combat manouvers) must have to add to the evaluation.

Another issue: i don't undestrand the strange british politic about the 12.7 mm: if the P-40 had them, why do not look to add them on their Hurricanes and Spitfires, atlest while waiting for the HS 404? Soviet did differently, as example, filling the Hurricanes with 12.7 or 20 mm guns.

As firepower 'bigger is better' theory: OTOH, the bigger caliber can pierce armour. And, with HE, can break the target, often in a explosive manner. This is also a powerful impression of their effectiveness. The LRM fire was often, just to shot peas (bombers survived to hundreds impacts).

About the 'statistics': who cares really, if you cannot evalue 'how you shot' to the targets! Just think to some 'ace in a day' pilots: how did they manage to do this, just 'statistically' they should have obtained 0,5-1 kills with all their ammunition. And then, what about Marseille, McConnell, Vraciu (shot down six Judy in minutes!) and so on? If you start to fire behind a bomber, let's say at 500 meters/yards, then you'll obtain not much against it. But if you manage to shot at him in a frontal engagement, then you'll obtain much more with a 1-2 second burst, than emptying the whole magazines while firing from behind and 300-500 meters awas! It's a matter of ability, not just firepower and statistics. IOW, you cannot really conclude if, a pilot would shot down zero or seven aicraft during a mission, just looking at the statistics.

 

You raise so many issues that it would take me a few pages to answer them all - although if you read through all of the following you should learn a lot:

http://www.quarry.ni...W2guneffect.htm

http://www.quarry.ni...k/CannonMGs.htm

http://www.quarry.ni...co.uk/ideal.htm

 

The Hispano was not designed for wing-mounting and had particular installation requirements which meant it had to be fine-tuned for each type of aircraft. This was not understood at first, which was part of the reason why the initial Spitfire installation in summer 1940 was so unreliable (the other part being that the guns were mounted on their sides, which they really didn't like). When installed in the fuselage of the Beaufighter later the same year they worked much better, and they seemed OK in the Whirlwind too. 

 

60 rounds was too small but the RAF got the belt-fed version in as soon as they could. Interestingly, combat analysis later showed that only 90 rounds per gun were perfectly adequate for the great majority of missions. 

 

The Zero pilots who preferred to use the 7.7mm MGs rather than the 20mm were experts who were only attacking early-war planes with little or no armour, and the 20mm were low-velocity types. As planes grew tougher they dropped the 7.7mm for 13mm and upgraded the 20mm to higher-velocity versions.

 

According to the USN, the 20mm was three times as effective as the .50, not twice as much as you suggest. The destructive effect of 20mm shells compared with 12.7mm is clearly shown by the preference of those air forces which had a free choice of both: the 20mm ShVAK was installed where possible, despite the 12.7mm Beresin being lighter, faster-firing and having a higher muzzle velocity. Similarly, the 20mm MG 151 was preferred over the 15mm version despite having a lower velocity.

 

The British didn't fit .50 "while waiting for the 20mm" because they didn't have any. The Hispano was already in UK production in 1940, the .50 wasn't and the US needed all of theirs to equip their growing forces. Only later in the war did some .50s become available, for installation in bomber turrets and in some Spitfires.

 

We can agree, however, that pilot skill was of far greater importance than any other factor in determining success. 



#144 Tony Williams

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Posted 30 September 2013 - 0209 AM

The 37mm on a MiG was generally a heavy bomber killer. Later variants of MiG 17 switched from 1x37mm and 2x23mm to 3x23mm (before going whole hog with missiles).

 

Given that the MiG's weapon pack (-15 and -17) had one 37mm on one side and two 23mm on the other, I have observed before that it would have made more sense to change the armament to four 23mm for anti-fighter use or two 37mm for the anti-bomber role.



#145 Tony Williams

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Posted 30 September 2013 - 0210 AM

By the way re. armament, a question about the Spitifres: The "C" type wing (Universal) allowed mounting 4x20mm Hispano while keeping gun bays for 4x.303 in the outer wing. Was a combination of 4x20mm and 4x.303 ever used or was it in practice strictly exclusive (ie either 4x20 or 2x20 + 4x.303)?

 

Not that I've ever heard. As I've observed previously, four 20mm was one heck of a load for the little Spitfire and rarely carried.



#146 istvan47

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Posted 30 September 2013 - 1639 PM

Tony, i have already read them, but the point such: 1x 20 mm is like 3x12.7 mm is quite too generalized, not?

I mean, a 20 mm is MG FF with 60 rds just like the MG 151/20 with 250 rds. I wouldn't be sure, about the superiority of the 20 mm MG FF vs 12.7 mm, not surely 3x!

If you have just 60 rds for each gun, i would not that sure that the Spitfire was better served than a P-40 with 6x12.7 mm.

The Finns that replaced the HS 404 with a 12.7 mm is an example quite interesting, i'd say.

BTW: British made the Vickers 12.7 mm, why not use them? Or also, licence-building the 0.50 Browning? Why not, as the smaller 0.30 was already made?

Edited by istvan47, 30 September 2013 - 1815 PM.


#147 Marek Tucan

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Posted 30 September 2013 - 1741 PM

because they made the leap from .303 outright to 20mm (bringing in .50 later as an "afterthought")... And Vickers .50 was pretty slow-firing and with not too good ballistic performance.

 

What might be interesting would be a MG in 15mm BESA, but it would probably end like German 15mm - too much gun for too little bullet.

 

EDIT: For the comparison, it is generally possible between similar-era weapons. 20mm MG FF may sound like not much, but if you measure it against rifle caliber MGs or low velocity 12.7/13.2 MGs, it comes on top... And same situation is later with modern 20mm (151/20, ShVAK and Hispano II) and .50


Edited by Tuccy, 30 September 2013 - 1744 PM.


#148 istvan47

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Posted 30 September 2013 - 1813 PM

Maybe! But yet, the USN that evalued the A6M Zeros often wrote that they had a low firepower.

Even if 2x20 mm = 6x12.7 mm.

Another ones: some USN aviators complained about the firepower of the F4U all guns, apparently they liked more the 12.7 mm versions, both as fire endurance and reliability.

This should give in count, as well.

P-47 were much appreciated as well, i've read about the effectiveness of their weapon set. Some pilots liked it more than the 20 mm guns.


'''''As far as we know the cannon was in some respect unreliable. It is said that the trigger mechanism could jam totally, or it fired only one shell and then jammed.

Antti Tani: It is true that it was a fairly ungrateful device. The 12.7mm machine gun that was introduced later was much better. It worked. Also the ammo capacity (of the cannon) was unreasonably small, it was, let me think, 50 shells. You could spend it in a couple of seconds. One burst, missing the target by accident, and the ammunition was spent. You then had to do with the wing guns and they were what they were. At the beginning of the war you could hit something with them, because the barrels were not full of sand. But after the Moranes took off from Naarajärvi for example, there was so much dust in the air that the next one had to wait for half an hour almost - if the weather was calm, you could not see anything.''''

http://www.virtualpi...ariEnglish.html


'''Antti Tani: The longest range ever was when I fired at that Pe-2 above Äanislinna (Petrozavodsk) at 500m. The deflection was so large that I did not use the gunsight but used the cockpit canopy frame for deflection. Three bursts I fired, first aiming with the edge of the gunsight, then I aimed between the gunsight and the canopy frame and finally at the frame. Then I did hit him. The pilot took a bullet through his head and that was it.
Was it the Berezina gun or the cannon ?
Antti Tani: It was the 12.7mm (Berezina). Had it been the cannon, its ammunition would have been spent with the second burst and I would have been out of ammunition. Fortunately I had the 12.7'''


So 12.7 mm Berezin Whipped the HS-404 in the FAF service!

Edited by istvan47, 30 September 2013 - 1824 PM.


#149 CaptLuke

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Posted 01 October 2013 - 0007 AM

According to the USN, the 20mm was three times as effective as the .50, not twice as much as you suggest. 

 

Hi Tony: one aspect of this I don't recall we've discussed is whether the USN assessment included the late war API .50 ammunition.  I've seen some discussions that said the AAF pilots thought the M8 was a breakthrough in effectiveness (can't find them now of course . . .).  The argument would be that as long as the M8 has sufficient penetration to get to something flammable and then has sufficient incendiary compound to start a fire, the added penetration/damage/fire starting capability of the 20mm isn't as big an advantage as a linear comparison would suggest.

 

I ran across another person who was saying that the M8 lost a lot of its incendiary capability over 35K feet (not enough oxygen) and against the lower grade jet fuel (vs. very avgas), which would be consistent with it becoming ineffective by Korea (in addition to just the heavier structure of the jets).  The issue with lower performance vs. jet fuel is consistent with other things I've seen, so that one at least I believe.

 

 

 

Just wondering.



#150 Sebastian Balos

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Posted 01 October 2013 - 0415 AM

Tony, i have already read them, but the point such: 1x 20 mm is like 3x12.7 mm is quite too generalized, not?
 

 

Check Table 2, gun power in:

 

http://www.quarry.ni...W2guneffect.htm

 

The analysis Tony did is pretty accurate. So, e.g. MG151/20 vs .50 M2 is around 3:1, while SHVAK vs UB is around 2:1.



#151 Tony Williams

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Posted 01 October 2013 - 0823 AM

Tony, i have already read them, but the point such: 1x 20 mm is like 3x12.7 mm is quite too generalized, not?

I mean, a 20 mm is MG FF with 60 rds just like the MG 151/20 with 250 rds. I wouldn't be sure, about the superiority of the 20 mm MG FF vs 12.7 mm, not surely 3x!

If you have just 60 rds for each gun, i would not that sure that the Spitfire was better served than a P-40 with 6x12.7 mm.

The Finns that replaced the HS 404 with a 12.7 mm is an example quite interesting, i'd say.

BTW: British made the Vickers 12.7 mm, why not use them? Or also, licence-building the 0.50 Browning? Why not, as the smaller 0.30 was already made?

 

The USN report was concerned with comparing their own guns, so the 20mm referred to was the AN-M2 (aka Hispano-Suiza HS 404). The tables in my article on gun effectiveness show you that not all 20mm were equal, just as not all HMGs were.

 

The HS 404 was a heavy gun, about twice the weight of the .50 M2, so with less powerful aircraft compromises had to be made between firepower and performance. 



#152 Tony Williams

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Posted 01 October 2013 - 0828 AM

'''Antti Tani: The longest range ever was when I fired at that Pe-2 above Äanislinna (Petrozavodsk) at 500m. The deflection was so large that I did not use the gunsight but used the cockpit canopy frame for deflection. Three bursts I fired, first aiming with the edge of the gunsight, then I aimed between the gunsight and the canopy frame and finally at the frame. Then I did hit him. The pilot took a bullet through his head and that was it.
Was it the Berezina gun or the cannon ?
Antti Tani: It was the 12.7mm (Berezina). Had it been the cannon, its ammunition would have been spent with the second burst and I would have been out of ammunition. Fortunately I had the 12.7'''


So 12.7 mm Berezin Whipped the HS-404 in the FAF service!

 

Only because of the limited ammo capacity in the initial, drum-fed form, which was replaced in RAF service from early 1941 by the belt-fed guns. So in fact, the drum feed saw relatively little use in the RAF.

 

And the 12.7mm Berezin was a rather better gun than the .50 M2. See my tables again.



#153 Tony Williams

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Posted 01 October 2013 - 0832 AM

 

According to the USN, the 20mm was three times as effective as the .50, not twice as much as you suggest. 

 

Hi Tony: one aspect of this I don't recall we've discussed is whether the USN assessment included the late war API .50 ammunition.  I've seen some discussions that said the AAF pilots thought the M8 was a breakthrough in effectiveness (can't find them now of course . . .).  The argument would be that as long as the M8 has sufficient penetration to get to something flammable and then has sufficient incendiary compound to start a fire, the added penetration/damage/fire starting capability of the 20mm isn't as big an advantage as a linear comparison would suggest.

 

I ran across another person who was saying that the M8 lost a lot of its incendiary capability over 35K feet (not enough oxygen) and against the lower grade jet fuel (vs. very avgas), which would be consistent with it becoming ineffective by Korea (in addition to just the heavier structure of the jets).  The issue with lower performance vs. jet fuel is consistent with other things I've seen, so that one at least I believe.

 

 

 

I think that the USN analysis took place before the M8 came out. Interestingly, the M8 was a copy of the Soviet B32 used in the Berezin.

 

The M8 was certainly the best all-round .50 aircraft ammo in WW2, but even so the RAF's 20mm SAPI ammo penetrated about as much armour and contained ten times as much incendiary material.



#154 Markus Becker

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Posted 01 October 2013 - 0845 AM

The M8 was certainly the best all-round .50 aircraft ammo in WW2, but even so the RAF's 20mm SAPI ammo penetrated about as much armour and contained ten times as much incendiary material.

 

 

 

 

Isn't armour penetration academic as in 'a moot point'?

 

Did any plane carry enough armour to stop a .50 cal? The Il-2's armoured bathtub was offering protection from rifle caliber ammo and 20mm shells didn't need to penetrate armour. They exploded and blew a part of the plane to bits.



#155 bojan

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Posted 01 October 2013 - 0923 AM

At odd angles 12.7mm could have problem with some of heavier armored planes. Re 20mm trowing bits of plane around, German 20mm AA switched to AP often when dealing with Il-2.



#156 Tony Williams

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Posted 01 October 2013 - 0954 AM

 

The M8 was certainly the best all-round .50 aircraft ammo in WW2, but even so the RAF's 20mm SAPI ammo penetrated about as much armour and contained ten times as much incendiary material.

 

 

 

 

Isn't armour penetration academic as in 'a moot point'?

 

Did any plane carry enough armour to stop a .50 cal? The Il-2's armoured bathtub was offering protection from rifle caliber ammo and 20mm shells didn't need to penetrate armour. They exploded and blew a part of the plane to bits.

 

 

Yes, penetration mattered especially against late-war planes which were better protected. You have to bear in mind that the projectiles usually had to penetrate the fuselage before reaching any armour and that frequently destabilised them so that they didn't hit the armour point-first. Furthermore, they would usually hit the armour at something less than 90 degrees. Put these two factors together and the actual penetration achieved was a small fraction of that measured in ideal conditions.

 

For example, in RAF tests carried out in January 1941 (described in my book Flying Guns WW2) .303 and 7.92mm AP ammunition was fired at the rear of a Blenheim fuselage on the ground, at a distance of 200 yards. The Blenheim was a flimsy plane which only had 4mm armour. However, only 23% of the 7.92mm bullets even reached the armour, and just 1% penetrated. This compared with penetration of around 12mm in ideal conditions.



#157 Markus Becker

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Posted 01 October 2013 - 1415 PM

Tony,

 

I read your article about the test with the Blenheim a long time ago and I always refer to it to illustrate the limitations of rifle caliber machine guns. But a 12.7mm bullet is something entirely different. A .50 BMG bullet has four/five times more kinetic energy and four times the weight, even though the diameter is only 50% bigger. This means A LOT more inertia and sectional density.

 

Simply put, a .50 cal will go right through an aluminum spar that could stop an 8mm bullet or at least make it tumble. Thus I assume the actual penetration of a .50 was much closer to the theoretical maximum([email protected]?).



#158 Sebastian Balos

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Posted 01 October 2013 - 1529 PM

After penetrating fuselage skin, even .50 received yaw, hitting armour e.g. sideways or at an unfavourable angle with severely degraded penetration compared to those 25 mm or so. 20 mm is an entirely different beast. Twice the round weight and a pretty blunt round shape enabled this.


Edited by Sebastian Balos, 01 October 2013 - 1531 PM.


#159 CaptLuke

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Posted 01 October 2013 - 2148 PM

 

 

According to the USN, the 20mm was three times as effective as the .50, not twice as much as you suggest. 

 

Hi Tony: one aspect of this I don't recall we've discussed is whether the USN assessment included the late war API .50 ammunition.  I've seen some discussions that said the AAF pilots thought the M8 was a breakthrough in effectiveness (can't find them now of course . . .).  The argument would be that as long as the M8 has sufficient penetration to get to something flammable and then has sufficient incendiary compound to start a fire, the added penetration/damage/fire starting capability of the 20mm isn't as big an advantage as a linear comparison would suggest.

 

I ran across another person who was saying that the M8 lost a lot of its incendiary capability over 35K feet (not enough oxygen) and against the lower grade jet fuel (vs. very avgas), which would be consistent with it becoming ineffective by Korea (in addition to just the heavier structure of the jets).  The issue with lower performance vs. jet fuel is consistent with other things I've seen, so that one at least I believe.

 

 

 

I think that the USN analysis took place before the M8 came out. Interestingly, the M8 was a copy of the Soviet B32 used in the Berezin.

 

The M8 was certainly the best all-round .50 aircraft ammo in WW2, but even so the RAF's 20mm SAPI ammo penetrated about as much armour and contained ten times as much incendiary material.

 

 

I understand your point but I'm saying that the big hurdle is "enough incendiary to start a fire" vs. "not enough incendiary to start a fire."  There's a big binary hurdle where there is a step change in effectiveness, not a linear change.   If the M8 starts a fire and the 20mm starts a fire, the important thing is the fire.  It is a secondary consideration that the 20mm induced fire starts bigger because of the extra incendiary material.

 

Conversely, if the 20mm SAPI has enough incendiary material to start a fire and the M8 does not, the 20mm is not 10 times as effective, it is more like 100 times as effective because a fire kills an airplane but a hole does not.

 

I'm not suggesting that this equalizes things between the .50 and the 20mm Hispano, you've got me convinced on that argument.   My point is that the given good API ammunition, the difference between the 20mm and the .50 may be less than the a linear numerical comparison shows, especially against lighter planes using high octane avgas below 30,000' and that this, in addition to the other factors you've done a very good job enumerating, may help explain the late war AAF (later USAF) attachment to the .50



#160 Brian Kennedy

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Posted 01 October 2013 - 2217 PM

Wouldn't the fact that Japanese planes were so lightly built be an issue too? If you're fighting zeros or oscars -- planes that are tough to hit but can't withstand much damage -- seems to me that you'd go for a high rate of fire instead of destructive power per round.




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