Aircraft gun article

[Squire]

I actually think the real end to the .50 came with the Jet Age, where time on target issues began to make things more difficult, ala MiG-15 vs F-86, and the adoption of "cannon only" really came into being post WW2.

As far as the ammo issue goes, I also think that is a relevent partial defence of the 12.7mm, you did tend to get almost twice the ammunition as a 20mm in many fighters, but that only offsets it somewhat.

Still an interesting debate.

[Knegel]

Hi,

Yep, i agree, in the jetage, when cannons with less relative weight, more reliability and ROF got produced, the MG´s got obsolet, specialy if we see that all nations (at least west allieds and east allieds) got tough bombers.
But its very interesting to see that the F-86 still did carry 6 x .50cal and was rather successfull vs the MG-15. VS fighters with probably easy to damage jet engines the .50cal still seemed to work pretty good.  

Dont the north coreans had tough bombers?

Greetings, Knegel

[Tony Williams]

Originally posted by Squire
Btw, its interesting to note that the axis did not go to an all 20mm force in most of their fighters, Fw190, Bf109, Ki-84, Ki-61, Ki-44, A6M (later), MC series, all employed either 12.7 or 13.1mm weapons. So they obviously thought they were good for something, and not just "useless weight". The Soviets used 12.7s on many fighters as well.  

In the case of the German planes, the reason is simple: there was no room to fit cannon in the space for the synchronised cowling guns. The little 13 mm MG 131 was the biggest gun which could be fitted there, until the long-nosed Ta 152 and Do 335 came along, but they never saw service.

Tony Williams: Military gun and ammunition website and discussion forum

[Tony Williams]

Originally posted by Knegel
But its very interesting to see that the F-86 still did carry 6 x .50cal and was rather successfull vs the MG-15. VS fighters with probably easy to damage jet engines the .50cal still seemed to work pretty good.  

Actually the armament of the F-86 was considered unsatisfactory by the USAF - it took over 1,000 rounds fired to down a MiG-15 on average, and many MiGs got home despite being hit by up to fifty bullets. As a result, the USAF initiated Project GunVal, in which they fitted 20mm cannon  to some F-86s and sent them out for operational testing in Korea. The USAF switched to 20mm for all new planes after that.

Fortunately for the USAF, the MiG-15 also had unsatisfactory armament for the opposite reason; its heavy, low-velocity cannon were designed to shoot down bombers and it was difficult for them to connect with with Sabres.

Tony Williams: Military gun and ammunition website and discussion forum

[HoHun]

Hi Squire,

>I actually think the real end to the .50 came with the Jet Age, where time on target issues began to make things more difficult, ala MiG-15 vs F-86, and the adoption of "cannon only" really came into being post WW2.

Well, "the end" really came in the Korean war, but only because the USAF didn't understand the message in WW2. They were pretty disappointed by their 12.7 mm machine guns in Korea though they were using a version with considerably increased rate of fire - I'm sure you are aware of Project GUNVAL which was initiated to rush the 20 mm cannon into service quickly.

>As far as the ammo issue goes, I also think that is a relevent partial defence of the 12.7mm, you did tend to get almost twice the ammunition as a 20mm in many fighters, but that only offsets it somewhat.

I'm afraid it only looks like that as long as the weight penalty is accepted. If you look at batteries of equal weight, the heavy machine gun actually has the poorest endurance:

1x MK 108 - 634 rpg - 431 kg - 295% firepower - duration of fire: 63 s
1x MK 103 - 314 rpg - 430 kg - 240% firepower - duration of fire: 44 s
2x MG 151/20 - 811 rpg - 431 kg - 149% firepower - duration of fire: 67 s
2x Hispano V - 705 rpg - 431 kg - 145% firepower - duration of fire: 58 s
2x Hispano II - 673 rpg - 431 kg - 125% firepower - duration of fire: 67 s
2x MG-FF - 553 rpg - 430 kg - 92% firepower - duration of fire: 69 s
4x MG 151 - 361 rpg - 431 kg - 103% firepower - duration of fire: 30 s
8x MG 131 - 472 rpg - 431 kg - 99% firepower - duration of fire: 31 s
6x ,50 Browning M2 - 390 rpg - 431 kg - 100% firepower - duration of fire: 30 s
12x Browning ,303 - 863 rpg - 431 kg - 62% firepower - duration of fire: 43 s

In other words, if a 20 mm battery had only half the endurance of a machine gun battery, this was the result of a design choice that either preferred light weight over endurace or (more likely if we're talking about the 4 x 20 mm installations) firepower over endurance.

I don't know if you have seen the chart with the burst limits for the 12.7 mm machine gun that had to be observed to avoid overheating and "cook-offs". You could fire a 15 burst round, than pause 30 s, fire the next 15 burst round, and so on - and after 10 secondary bursts fired that way, the barrel would be so hot that you'd have to stop anyway (165 rounds in five minutes).

If the pauses were extended to 60 s, you could start with a 75 round burst, then fire 10 secondary bursts of 15 rounds each. (225 rounds in 11 minutes).

That doesn't look to me as if 390 rounds per gun as outlined above were likely to be expended. I believe Tony has posted once about the British Operations Research people tracking how many rounds of ammunition the bomber gunners were bringing back after an engagement with Luftwaffe night fighters - it would be interesting to know if similar evaluations were done for fighter guns!

Regards,

Henning (HoHun)

[Knegel]

Originally posted by Tony Williams
Actually the armament of the F-86 was considered unsatisfactory by the USAF - it took over 1,000 rounds fired to down a MiG-15 on average, and many MiGs got home despite being hit by up to fifty bullets. As a result, the USAF initiated Project GunVal, in which they fitted 20mm cannon  to some F-86s and sent them out for operational testing in Korea. The USAF switched to 20mm for all new planes after that.

Fortunately for the USAF, the MiG-15 also had unsatisfactory armament for the opposite reason; its heavy, low-velocity cannon were designed to shoot down bombers and it was difficult for them to connect with with Sabres.

Tony Williams: Military gun and ammunition website and discussion forum

Hi,

afaik the two 23mm cannons was high velocity guns, but low in ROF. The 37mm was low in both aspects.

Since the cannons did suffer the same problem, i guess the needed 1000rounds was more caused by the poor hitprobability while fighting at highspeed than by missing damagepower.

I only wonder if the NATO didnt expected to meet more tough targets than a Mig-15. What they thought to do vs big and medium Bombers??

Greetings, Knegel

[Tony Williams]

Originally posted by Knegel
afaik the two 23mm cannons was high velocity guns, but low in ROF. The 37mm was low in both aspects.

The 23x115 ammo fired by the MiG was a low-velocity round (690 m/s, the same as the N-37's 37x155), not at all the same as the much more powerful 23x152B fired by the WW2 VYa-23. Two 23mm guns were used in the MiG-15; initially they had the NS-23 (550-700 rpm), but the MiG-15bis had the NR-23 (850-950 rpm). The N-37 fired at 400 rpm.

Since the cannons did suffer the same problem, i guess the needed 1000rounds was more caused by the poor hitprobability while fighting at highspeed than by missing damagepower.
[/B]

That would have been the major cause, but note that I said that MiGs got back after receiving up to 50 hits. MiG pilots also reported seeing the .50 bullets deflected off their planes. This may sound odd, but the metal skinning of the jets was much tougher than WW2 prop planes, and the bullets would often strike at a very fine angle so could be deflected without penetrating. When you look at the back view of a MiG, you'll see what  mean.

Tony Williams: Military gun and ammunition website and discussion forum

[HoHun]

Hi Tony,

>Fortunately for the USAF, the MiG-15 also had unsatisfactory armament for the opposite reason; its heavy, low-velocity cannon were designed to shoot down bombers and it was difficult for them to connect with with Sabres.

Hm, maybe you have better sources, but I have a GDR booklet here that describes the performance of the Soviet guns in Korea as superior. It also mentions that the cannon were the result of a deliberate switch to medium velocity in order to maximize rate of fire while reducing weight. Now that might have been propaganda, but while the USAF completely got rid of what had been their primary air-to-air weapon, the Soviets continued to design medium-velocity guns for their fighters, like the NR-30 for the MiG-19 and the NR-23 for the MiG-21.

If for example instead of 3 x NR-30, they would have installed 2 x NR-30 and two smaller-caliber high-velocity guns in the MiG-19, we'd have an hint they were disappointed with the performance of their guns, but as it is, no paradigm change (as with the USAF) took place after Korea.

>MiG pilots also reported seeing the .50 bullets deflected off their planes. This may sound odd, but the metal skinning of the jets was much tougher than WW2 prop planes, and the bullets would often strike at a very fine angle so could be deflected without penetrating.

Actually, this effect had been observed in WW2, too.

Regards,

Henning (HoHun)

[Grendel]

Originally posted by Knegel


And it looks like he realy think a nation, which did pop out CV´s, many other ships, thousands of Bombers, fighter, tanks etc, one after the next, wouldnt have been able to introduce a 20mm in big numbers, if there would have been a real need.  

If you read the articles available on for example Emmanuel Gustin's and Tony's web pages or the Flying Guns: World War II book you'll find excellent expnalation how such a nation was not able to introduce the 20mm cannon in big numbers because technical problems. Another reason was of course the logistics.

Btw, 2 x Hispano II(dont the US 20mm had a smaler ROF?) would have provided around a 4 times smaler armament-hitprobability  than the 6 x .50cal, without to consider the shorter time to shoot,  vs smal fighters this would have been a pretty bad handycap.

Nope. With machineguns you'll need to put a long burst into the target, yet there are no guarantees of it going down.  Machinegun bullets do minimal damage on their own, and there must be lots of them hitting the target to cause damage. And for example, especially if shot from rear angles most bullets tended to deflect from airplane's surface, even from fabric surface, or tumble after penetrating, causing the bullets to lose much of their power. One Allied study showed that only 3% of .50 bullets fired from rear damaged critical items, pilot or control cables inside fuselage. Rest just deflected or made holes to the airplane skin, nothing else.

With a cannon there are fewer bullets in the air, but when those hit they make immediate damage.

What point there is if you can hit the enemy plane, but can't kill it?

All air forces acknowledged the need for destructive power, instead mass of bullets, either during or after the WW2, and some only during the Korean war.

[indy007]

Originally posted by Knegel
Hi,

Yep, i agree, in the jetage, when cannons with less relative weight, more reliability and ROF got produced, the MG´s got obsolet, specialy if we see that all nations (at least west allieds and east allieds) got tough bombers.
But its very interesting to see that the F-86 still did carry 6 x .50cal and was rather successfull vs the MG-15. VS fighters with probably easy to damage jet engines the .50cal still seemed to work pretty good.  

Dont the north coreans had tough bombers?

Greetings, Knegel

At jet dogfight altitudes, the API rounds from the Sabre's had severe problems getting ignition. You could chew off chunks of the MiG, but they'd just soak it up and keep flying. What let the Sabres down so many Migs was the radar gunsight. If I've got a radar gunsight, and you've got the Mk1 eyeball, in a dogfight with 1000mph closure rates, I've got an extreme advantage over you, cannons or not.

[Karnak]

Originally posted by Knegel
Btw, 2 x Hispano II(dont the US 20mm had a smaler ROF?) would have provided around a 4 times smaler armament-hitprobability  than the 6 x .50cal, without to consider the shorter time to shoot,  vs smal fighters this would have been a pretty bad handycap. 4 x 20mm would have been needed, but this would have increased the weight and reduced the ammo load, and wouldnt the long barrels also decrease the performence(afaik it did in the SpitVa to SpitVb, or was it the weight?)?

Why do you keep repeating this debunked argument?  It has been demostrated to be absolutely false, yet you keep repeating it?  Do you actually read what others have said?  You keep talking about RoF of the instalation like there are bullets flying out randomly in sphere, thus crediting RoF with a direct coralation to chance to hit.

[The gun instalations produce a bullet stream.  This is true of both the .50s and the 20mm cannons.  Both have a high enough RoF to stop the target from being able to fly between the shots with the possible exception of near 90 degree crossing shots, which in WWII resulted in less than 1% of shoot downs.

Therefore your main claim to the superiority of the .50 is that in less than 1% of cases it will hit and the 20mm will miss.  TO hold that sub 1% as the deciding issue when all of the other strengths of the 20mm have been covered is ridiculous.

If a shot will hit with a six pack of .50s it will almost certainly hit with a two pack of Hispanos, and do more damage at the same time.

[Tony Williams]

Originally posted by HoHun
Hm, maybe you have better sources, but I have a GDR booklet here that describes the performance of the Soviet guns in Korea as superior. It also mentions that the cannon were the result of a deliberate switch to medium velocity in order to maximize rate of fire while reducing weight.

Well yes, it didn't happen by accident The issue is whether the decision was the right one. I don't think that a GDR source can be taken as unbiased.

There are really three separate issues here: the performance of the gun (power/weight ratio), the performance of the ammo, and the gun selection for the aircraft. Like most Russian guns, the NR-23 and N-37 were good. The NR-23 fired more quickly than the Hispano, for less weight, and the shells were much heavier. The N-37 was also quite a remarkable performer; compared with the US equivalent, the 37mm M10, the weight was the same, the ammo 1.5x more powerful and the RoF 2.5x faster.

But the choice in both calibres of a heavy shell/low velocity combination was better suited for attacking bombers rather than agile fighters.

I have no doubt that the MiG-15 would have been far more appropriately armed for dealing with fighters if it had four NR-23. Better still if the projectile weight had been dropped to boost the muzzle velocity.

Now that might have been propaganda, but while the USAF completely got rid of what had been their primary air-to-air weapon, the Soviets continued to design medium-velocity guns for their fighters, like the NR-30 for the MiG-19 and the NR-23 for the MiG-21.

The NR-30 was an excellent gun with a remarkable power/weight ratio (three of them weighed the same as two 30mm Aden revolver cannon, fired at least as quickly, and used much more powerful ammo), but it's worth noting that the muzzle velocity was usefully higher than the earlier cannon, even though the shell weight was still high.

I don't think that the MiG-21 ever carried the NR-23; that gun was obsolete by then. It started with the NR-30, went gunless for a period, then adopted the little GSh-23, which fired basically the same ammo as the NR-23 for little more weight, but at 3,000 rpm...

Tony Williams: Military gun and ammunition website and discussion forum

[HoHun]

Hi Tony,

>I don't think that a GDR source can be taken as unbiased.

Well, in this case it is matched the realities of Soviet weapon development, so it wasn't all wishful thinking.

When it praises the MiG-21 and MiG-23, and then there is the paradigm change to the MiG-29, that's the point where one should get suspicious :-)

>But the choice in both calibres of a heavy shell/low velocity combination was better suited for attacking bombers rather than agile fighters.

Actually, 690 m/s is not so far from the ca. 750 m/s of the MG 151/20, and that was an excellent anti-fighter weapon. High muzzle velocity is not as important in fighter-vs.-fighter combat as the ability to make the most out of time-limited shooting opportunities.

The way to kill an evading fighter is to hit him hard when he momentarily presents a good target, for example a large planform or a low deflection, or when he manoeuvres in only one plane for an instant. You can anticipate these opportunities for some fractions of a second (enough to make muzzle velocity secondary), but there is no way you can extend the duration of these moments, so you want a weapon with great knock-down power against fighters just the same as against bombers.

When talking about air-to-air gunnery, people seem to be fixated at maximum effective range, but in practice, the range of maximum effectiveness has much more relevance - and that is much shorter regardless of the muzzle velocity.

>it's worth noting that the muzzle velocity was usefully higher than the earlier cannon, even though the shell weight was still high.

Well, 780 m/s to 690 m/s according to my GDR booklet, useful but still in the same class. No paradigm change for sure.

>I don't think that the MiG-21 ever carried the NR-23; that gun was obsolete by then.

You are right, I thought of the twin-barrel cannon but erroneously kept using the NR-23 designation. Anyway, still in the same class muzzle-velocity wise.

Regards,

Henning (HoHun)

[gripen]

Originally posted by HoHun
The way to kill an evading fighter is to hit him hard when he momentarily presents a good target, for example a large planform or a low deflection, or when he manoeuvres in only one plane for an instant. You can anticipate these opportunities for some fractions of a second (enough to make muzzle velocity secondary), but there is no way you can extend the duration of these moments, so you want a weapon with great knock-down power against fighters just the same as against bombers.

Hm... In the case of the MiG-21 (NR-30 or GSh-23canon) the pilot have a luxury of the gyroscopic gun sight with automatic range measuring. That makes the high velocity of the projectiles less important than it was in the WWII fighters.

gripen

[Tony Williams]

Originally posted by HoHun
Actually, 690 m/s is not so far from the ca. 750 m/s of the MG 151/20, and that was an excellent anti-fighter weapon. High muzzle velocity is not as important in fighter-vs.-fighter combat as the ability to make the most out of time-limited shooting opportunities.

The MG 151/20 was a good anti-fighter weapon in WW2, when aircraft speeds were much lower. As they increased and firing opportunities became briefer, so a reduced projectile flight time became more useful.

The RAF did some studies of gun armament in the 1950s (by which time they had adopted the 30mm Aden) and ran all sorts of simulations to determine what would be the best way of improving the kill probability of the armament: larger calibre? Higher rate of fire? Or higher velocity? They concluded that a higher velocity would be most useful  - but of course, the Aden of the time was a low-velocity piece, and its calibre was already sufficient.

It's fair to say that there are currently two different views on muzzle velocity: the Russians, who still favour heavy shells at medium velocity (the current 30mm GSh-301 has an MV of 860 m/s) and the West, which prefers at least 1,000 m/s velocity.

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