Armor Penetration - 20mm vs. .50 cal. (3 Viewers)

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it is apples and oranges to me. I've made my argument about the weight of the machine guns, which like i said before, was extraneous, when considering the reliability of the .50 cals vs the 20mm tendency to jam.

"Better range" meaning, they could shoot a burst in front of a target and the plane would fly through a stream of bullets.
It would be very wasteful to use cannons in that manner, so it often required a closer shot, and many times wasn't the choice weapon for air to air combat, until later in the war when fire rates and reliability had improved.

You can go on and on about the weight, but it s extranious to mention the weight considering the obvious benefit of having a large ammo supply and the ability to fire at 800rpm. Cannons didn't reach this fire rate until later in the war when, you started to see them on F4s.....



(I don't actually think there was a worthwhile difference in trajectories between the 12.7 mm Browning and the 20 mm Hispano II, by the way.)
It is a notable difference as the 20mm began to fall away from its target and had a greater arc when firing in turns, primarily because of the weight of the shell.


i feel like i'm repeating myself.:lol:
 
Hi Bill,

>I've made my argument about the weight of the machine guns, which like i said before, was extraneous, when considering the reliability of the .50 cals vs the 20mm tendency to jam.

The 20 mm Hispano II in British use seems to have been perfectly reliable (details on Modifications and Attempts at Standardization ), so this was not a question of the calibre, but of the way the gun was built.

>"Better range" meaning, they could shoot a burst in front of a target and the plane would fly through a stream of bullets.

Hm, that's not really literally what "better range" means :) However, the same technique works just as well with cannon.

>You can go on and on about the weight, but it s extranious to mention the weight considering the obvious benefit of having a large ammo supply and the ability to fire at 800rpm.

Your point about the weight of the ammunition is a very good one :) However, if you look at the weight of equivalent supplies, you'll find that cannon are at an advantage again:

8x ,50 Browning M2 - 425 rpg @ 136 g = 462.4 kg total, 33 s duration - 2,3 MW firepower - 74,2 MJ total energy
2x Hispano II - 350 rpg @ 246 g each = 172.2 kg total, 35 s duration - 272 kg - 2,1 MW firepower - 74,3 MJ total energy

So the equivalent ammunition supply in cannon shells weighs less than half of what the original machine gun supply weighed.

Oh, and rate of fire is just one component of firepower, the other is effectiveness of the individual round. That's how cannon make up for their lower rate of fire.

Regads,

Henning (HoHun)
 
Hi Bill,

>>(I don't actually think there was a worthwhile difference in trajectories between the 12.7 mm Browning and the 20 mm Hispano II, by the way.)

>It is a notable difference as the 20mm began to fall away from its target and had a greater arc when firing in turns, primarily because of the weight of the shell.

Hm, strictly speaking when firing in turns, the "falling away" of the projectiles an optical illusion created by the aircraft nose turning on, and thus independend of the weight of the shell :)

But the flight times of the 12.7 mm Browning and the 20 mm Hispano projectiles differ only very slightly, by about 10 % at 400 m range, so the effect really is very small.

By the way, here is the British data on the successful shoot-down range against fighter-sized targets:

The table (1 - 2 % inaccuracy due to rounding in the original report):

600 yards and less: 96 %
400 yards and less: 86 %
300 yards and less: 74 %
200 yards and less: 52 %

It would be rare to kill something beyond 400 yards, and even rarer to do so by firing from a turn.

(The corresponding Soviet data also linked in this thread shows even shorter ranges, by the way.)

Regards,

Henning (HoHun)
 
The 20 mm Hispano II in British use seems to have been perfectly reliable (details on Modifications and Attempts at Standardization ), so this was not a question of the calibre, but of the way the gun was built.


uhhh.....hmmmmmm. you might want to re-read your source, sir.

This is a great article. Good find, and if you look more closely the British continued to use the 20mm even though it was not perfectly reliable. Americans refused to use the guns, and maybe the British had a different idea of what reliable was, citing many misfires, fire stoppages, and mechanical failures after prolonged use.
The British worked through the problems encountered developing the munitions as well as the guns, which continued through out the war, and the 20mm cannon was never quite perfected until after the war was well over.

Re-read the aritcle. Just because the Britsh chose to use the 20mm, doesn't mean it was reliable. lol
 
The table (1 - 2 % inaccuracy due to rounding in the original report):

600 yards and less: 96 %
400 yards and less: 86 %
300 yards and less: 74 %
200 yards and less: 52 %

It would be rare to kill something beyond 400 yards, and even rarer to do so by firing from a turn.

Hi HoHun. I'm a complete novice, but considering gravity drop, is the 20mm cannon a more "accurate" weapon when aiming?...

 
Hi Bill,

>Good find, and if you look more closely the British continued to use the 20mm even though it was not perfectly reliable.

There are numbers in the article, and you'll find that the rate of stoppage in the US guns was six times as high as that in the British guns. With one stoppage per 250 rounds in that test, the British gun was certainly good enough for operational use. Their use in combat certainly was considered successful, even if there were some stories about stoppages for example in the defense of Malta. However, you'll also find stories about failures of the "reliable" 12.7 mm machine guns, for example in the F4F, but also in the P-51C and even in the supposedly fixed P-51D. Roger Freeman in "Combat Profile: Mustang" relates one example in which four or five out of the Mustang's six guns jams.

If you have data on the rate of stoppages of the war-time 12.7 mm Browning, bring it on - as far as I can tell, it was a gun like any other in that regard.

>Re-read the aritcle.

Bring on numbers.

Regards,

Henning (HoHun)
 
Hi Graeme,

>Hi HoHun. I'm a complete novice, but considering gravity drop, is the 20mm cannon a more "accurate" weapon when aiming?...

Though there are other factors, gravity drop is in fact one aspect.

However, it's possible to calculate approximate flight times from that table, and it seems that the Hispano 20 mm is considered to have a markedly higher muzzle velocity than the 12.7 mm Browning, which doesn't appear accurate.

What the tables illustrates nicely is that the difference between the trajectories of the 20 mm Hispano and the 12.7 mm Browning is small at typical combat ranges - 9 inches at 400 yards, where the pattern size alone is ten times that figure.

(What's the source of the table, by the way? Looks like an interesting docuement :)

Regards,

Henning (HoHun)
 
Hi Magister,

>Brits had to be concerned about German bombers. They didn't have a big ocean between them and Germany. 20mm is a great bomber killer tool.

And what is your source on the British reasons to adopt the 20 mm cannon?

Regards,

Henning (HoHun)
 
And what is your source on the British reasons to adopt the 20 mm cannon?

I don't have one. I also don't have a source for the Brits not having a big ocean between them and Germany. I take it we're OK on that one.

Would you be assuaged if I had predicated my comment with "Maybe" as in Maybe the Brits had to be concerned about German bombers. They didn't have a big ocean between them and Germany. 20mm is a great bomber killer tool.

In furtherance of this discussion, which is frankly just informed speculation, the Brits started the war off under heavy, devastating attacks from German bombers. "Maybe" that experience lingered in the formation of armament doctrine.

I think it was pretty well known that cannons performed much better against larger aircraft than MG. I don't have a source for you but the Brits performed tests on armor penetration and fuel talk rupturing ability between the .50 cal and 20mm.
 
Hi Magister,

>I don't have one.

I thought as much.

>I think it was pretty well known that cannons performed much better against larger aircraft than MG.

In fact, cannon performed much better against aircraft than MG, regardless of the size of the target.

As I have pointed out above, Luftwaffe combat experience as expressed in the belting orders in the "Schießfibel" shows that against fighters, the value of high-explosive shells was even greater than against bombers.

That cannon were dedicated anti-bomber weapons is a persistent but baseless myth.

Regards,

Henning (HoHun)
 
That cannon were dedicated anti-bomber weapons is a persistent but baseless myth.

Did I say that? The 20mm was more effective against all aircraft and more effective against bombers than the .303 or .50.

Again, I was just speculating. Not presenting fact. Why don't you tell us the real reason for the question that you presented (the British reasons for adopting the 20 mm cannon) with appropriate citations to sources.

I have speculated that Maybe the Brits had to be concerned about German bombers. They didn't have a big ocean between them and Germany. 20mm is a great bomber killer tool.

You have responded, if I am not misunderstanding you, that such considerations are a myth. I take it that your assertion, unlike mine, is not presented as a "maybe" but as a fact.

Please explain with appropriate citations to evidence establishing that such considerations played no roll at all.

(Note that I never ever speculated that 20mm cannon usage was employed for dedicated, 100% bomber killer reasons.)
 
Hi Magister,

>>That cannon were dedicated anti-bomber weapons is a persistent but baseless myth.

>Did I say that?

Did I say that you said that?

>Again, I was just speculating. Not presenting fact.

Obviously.

>Why don't you tell us the real reason for the question that you presented (the British reasons for adopting the 20 mm cannon) with appropriate citations to sources.

Go and do your own research - preferrably before you open your mouth again.

Kind regards,

Henning (HoHun)
 
Please explain with appropriate citations to evidence establishing that such considerations played no roll at all. I only speculated that it was a consideration. When I present reasons as fact, you'll know it.

On this forum we all (except for you, of course) speculate as to reasons for courses of action, performance of aircraft, etc. because we are dealing with less than complete and accurate information. If you don't like that, maybe you would be happier posting somewhere else.

Lastly, you be sure and get back to me when you have an answer (with appropriate evidentiary citations of course).
 
Incidentally, the .50 BMG guns, in 1944, had already reached their peak in design. It was understood that the ability to project greater lethality could really only be increased by the addition of more guns. Two options were being considered, at least by the Navy: (1) 20mm cannon which they already had and and (2) the 3,600 fps .60 cal gun that had begun development in 1941 but was still considered to be a year or more off.

The .60 cal gun had very impressive armor piercing capacity. 1.25" of armor at 600 yards at 20 degree obliquity. It's time of flight to 500 yard was just .45 seconds versus .62 for the .50 BMG. This was a very heavy projectile that weighed about the same as a 20mm round so it had an extremely high sectional density.

The .50 was not considered ideal by the USN. It was noted the .50 was more prone to having its barrel burned up from sustained firing than the 20mm and the 20mm had been adjudge as being much more effective.

Commander Monroe (Naval Armament Branch) also said:

"[T]he majority opinion (of ordinance men) is very enthusiastic about the 20mm gun. We have at present time (late October 1944) 200 Corsairs going out, at a rate of 50 per month, which will go into action as soon as we can get them aboard carriers to get an evaluation of the 20mm gun in the Navy fighter. I am personally very anxious for the first report on that, and I think the first time they open up on a Jap fighter, it's going to fly into a million pieces. We have a great cry for the 20mm gun."

Report of Joint Fighter Conference, p. 156-167
 
Hi Magister,

I notice that you edited your previous post after I answered. Any mismatch to my reply is your responsibility.

>Please explain with appropriate citations to evidence establishing that such considerations played no roll at all.

Did I say "no roll at all"? For someone who likes the "Did I say" game, you're taking surprising liberties at putting words into my mouth.

That's a dishonest discussion style which I do not appreciate, so you're on my ignore list now.

For the benefit of everyone else: That cannon are dedicated anti-bomber weapons has often been claimed, but never proven. Their universal use as anti-fighter guns is ample evidence that they were multi-purpose weapons. Magister has tried to narrow down this queston to the design intention, but my original statement was more general than that:

- "That cannon were dedicated anti-bomber weapons is a persistent but baseless myth."

Even ignoring the actual use and concentrating on the design intention (and being willing to actually do the research), Magister would not find more than a small share of the existing cannon types to have been developed as dedicated anti-bomber weapons. The German MK 101 or BK 5 might qualify, but browsing through Tony's "Rapid Fire", most cannon were developed as improvement over the guns already in service without a specialisation in target type in mind.

Since I guess I'd not perpetually face the same old myths and speculation here if Tony's work were better known, here is a link to his site which has quite a number of interesting articles on guns in general and aircraft guns in particular:

BOOKS BY ANTHONY G WILLIAMS

This article actually covers the introduction of the Hispano cannon into the RAF:

RAFHS 08

Something anyone interested in the topic might want to have a look at :)

Regards,

Henning (HoHun)
 
Hi again,

Hi Magister,

I notice that you edited your previous post after I answered. Any mismatch to my reply is your responsibility.

Oh, he just did it again. My response is based on his original post, and his original post was bad enough that I don't care for his revised post.

Regards,

Henning (HoHun)
 
Yes, I added:

On this forum we all (except for you, of course) speculate as to reasons for courses of action, performance of aircraft, etc. because we are dealing with less than complete and accurate information. If you don't like that, maybe you would be happier posting somewhere else.

Mismatch? How did this addition cause a "mismatch" between my post and your response? If I delete it, will it make you happy? Go take something for you sore vagina and take a nap.

Talk about a "mismatch" and "dishonest discussion style," where did I ever intimate that Brits use of the 20mm was "dedicated anti-bomber weapon"? Go read my post again spanky.

I now have you on "Ignore f-u-c-ktard" mode.
 
Though there are other factors, gravity drop is in fact one aspect.

However, it's possible to calculate approximate flight times from that table, and it seems that the Hispano 20 mm is considered to have a markedly higher muzzle velocity than the 12.7 mm Browning, which doesn't appear accurate.

What the tables illustrates nicely is that the difference between the trajectories of the 20 mm Hispano and the 12.7 mm Browning is small at typical combat ranges - 9 inches at 400 yards, where the pattern size alone is ten times that figure.

(What's the source of the table, by the way? Looks like an interesting docuement :)

Regards,

Henning (HoHun)

I certainly agree that the table shows that the trajectories of the two weapons are so similar over normal engagement distances so to make the difference almost irrelevant in normal combat. I also agree that the source of the table would be of considerable interest.
However your comment on the table seeming to assume that the 20mm had a markedly higher mv I find confusing. The results on the table are almost exactly what I would expect given the characteristics of the two weapons. Would you care to explain this comment you made?
 

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