Performance Comparison: Machine Guns and Light Cannon

[Shortround6]

B-17 with up to multiple 88 bits. From an old B-17 book I can look some video or pics on the web up and find the same though.
P47 one in the wing huge hole, another case 4 feet of wing gone, that is in Bob Johnson's book.

AS has been noted, you imply that P-47s took multiple 88mm hits but then change the story.

I am not refuse to acknowledge type of damage for the 20mm, I said is was designed for blast effect and as far as I can tell pre-fragmented warheads in 20mm were not used in WWII or at least very little. Most effort was of larger guns having VT fuzes

Who's 20mm shells were designed for blast effect? The German Mine shell was but the shells used by other nations or guns? You keep spouting off about pre-fragmented warheads but it was well known by the beginning of WW II that fragmentation could be greatly affected (if not actually "controlled")by the material, heat treatment and type of explosive used. The fragmentation difference between steel and cast iron is rather notable and even all cast iron is not the same.

"Needless to say HE shell design is not a simple matter, the strength of the steel body has to be balanced with the quantity, power and violence of the explosive to produce the desired fragmentation."
"However, in late 1944 a new and more powerful fill was adopted for shells - RDX/TNT and started to appear in small quantities in 1945, the reason for its introduction was improved fragmentation for anti-personnel effects by about 25%."

from:AMMUNITION

You seem to be saying that the shell body of a 20mm HE shell pretty much ceases to exist at the point of explosion and can be left out of the damage effects.

A German mine shell for the 20mm weighed 92 grams of which 20 grams was explosive, the fuse was a substantial part of the weight. let's assume 30 grams for now ( correction welcome), that leaves 42 grams of shell wall.
The British 20mm Hispano HE weighed 130 grams of which 10-10.5 grams was explosive, the fuse again was substantial and lets assume the same 30 grams for now, that leaves about 90 grams of shell wall or twice as much material for fragments as the German shell. It is also about twice the weight of a .50 cal bullet. What happens to these 90 grams of steel?turn to dust? splits into two large pieces?

Most 20mm shells used explosives about 15-25% more powerful than TNT.

There is a relationship between fragment size, number of fragments, shape, target, velocity, blast pattern.
Too large a fragment and it tends to miss, too small and more fragments tend to hit but do less or insufficient damage.

True but they do exist and have to be taken into account.

A time delay on a HE round gets the round inside to expand against the inside skins/structure (confined space). If it hits very closed to a structural element the blast may be high enough to fracture it.

Or, if fairly close (several inches?) a number of grams of steel moving at high velocity even if not a solid piece may fracture it or even carry away pieces of it much like a shotgun blast.

 

[zjtins]

From 20mm to 25mm - The Russian Ammunition Page
show 2 shells of 10 Russian used in WWII to be fragmented, I will see if I can find production rated or use rates.


http://en.wikipedia.org/wiki/MG_151_cannon
20mm German-no fragmentation listed for any shell

http://en.wikipedia.org/wiki/MK_108_cannon
30mm pict is smooth wall (minegeshoss)

True but they do exist and have to be taken into account.

But at what rate? Exploding on the surface and you have at least a 50% chance of all of the fragments missing the plane. Inside the few large fragment have to hit something vital or it just more holes the size the fragment.

OTOH a .50 will keep going until it goes through or hits something hard. So a rough comparison is a bunch of lines representing the .50 trajectory's going through the plane until it hits something. This in comparison to the 20mm HE which has spheres of influence where they blow up and then a couple lines from the fragments randomly expanded form the sphere. Those are the basic damage models that need to be compared, very difficult withe limited data to date.

 

[zjtins]

B-17 with up to multiple 88 bits. From an old B-17 book I can look some video or pics on the web up and find the same though.
P47 one in the wing huge hole, another case 4 feet of wing gone, that is in Bob Johnson's book.

Where did I say the P-47 took multiple 88mm hits??? it says a huge wing hole, another with 4 ft of wing gone, I never specified by what.
And the book has have many pictures and detailed descriptions of events. He shot down 28 plane and they are all in there.

Some battle damaged B-17's
http://www.daveswarbirds.com/b-17/contents.htm

P-47 damage
http://www.56thfightergroup.co.uk/aircraft.htm

A few more book with info-
The B-17: The Flying Forts
Zero, The Story of Japan's Air War in the Pacific-as Seen by the Enemy
Samurai!
Thunderbolt (Bob Johnsons book)
Fork-Tailed Devil: The P-38
Those are all Caidin's book's easy to find.


Just for kicks appear to be P-47 took a 88mm hit. Too much damage for a 37 mm.
http://www.ww2incolor.com/us-air-force/P-47+crash.html

Note: 88mm had impact and time delay. radar input to a mechanical calculator told the gun crews to set the timers and the ideas was to explode at a given distance.


British shell http://en.wikipedia.org/wiki/File:British_20_mm_Oerlikon_shell_diagrams.jpg

... However, shrapnel was not developed for any of the post World War I guns.

From http://shrapnel.askdefine.com/

 

[zjtins]

"However, in late 1944 a new and more powerful fill was adopted for shells - RDX/TNT and started to appear in small quantities in 1945, the reason for its introduction was improved fragmentation for anti-personnel effects by about 25%."

from:AMMUNITION

Appears to be artillery related, and the Germans used PETN anyway not sure of the Russian, Japaneese or US.

 

[Ivan1GFP]

Mod comment on the snarky reply?

Hello zjtins,
No insult intended for the "snarky reply". I believe you are arguing pretty much for the sake of argument without paying much attention to what these weapons actually do.

A single properly placed hit with a tiny weapon on an animal or an aircraft will take it down. A couple .30 cal rounds through the cockpit should kill the crew regardless of the size of the aircraft. An unexploded 105 mm AA shell through a wing probably won't do much. There are even cases of a .45 caliber pistol being used to bring down a fighter. These are all outliers and improbable events. Not impossible, just improbable.

If you look at photographs of the damage typically caused by a single hit by one of these aircraft (not heavy AAA) weapons, you will generally get a feel for the amount of damage typically done.

A .30 cal puts a hole like you might expect but it doesn't generally penetrate very deeply because it doesn't have the momentum..

A .50 cal puts a hole like you expect but generally penetrates a bit deeper. Italians and perhaps the Japanese used a pretty effective 12.7 mm explosive round which did a bit more.

A .20 mm cannon generally puts about a 6 inch hole into aircraft structure from the photographs I have seen. Yes, sometimes it's bigger, sometimes smaller.

A 30 mm cannon such as the MK 108 generally puts about a 3 foot diameter hole into the aircraft structure. It also isn't just a simple hole through the skin; the underlying structure is destroyed as well.

As I see it, there are lots of places on an aeroplane where you can punch a .30 cal or 1/2 inch hole without causing it to stop flying. When the hole gets to be 6 inches in diameter, there are fewer places that won't bring the plane down. When the hole gets to be around three feet in diameter, the number of places drops by a lot. With a bigger plane, obviously there are more places you can punch holes without killing it.

The Germans kept statistics on these things and their conclusion was that on the average, it took three 30 mm hits to bring down a heavy bomber but only a single 30 mm hit was needed to bring down a single engine fighter.

Japanese aircraft such as the A6M Type Zero had a few details that made them particularly vulnerable to a .50 cal: Most nations used "bags" suspended by straps for fuel tanks. The Japanese didn't; their tanks were often simple aluminum that filled the cavity they were placed in. When a high velocity bullet hits a "bag", the shock wave makes it expand a bit. When a HV bullet hits an aluminum tank, the shock wave ruptures it and if it is formed to the structure, may rupture the containing structure as well. The result is that you get much more than a 1/2 inch hole in the tank.

- Ivan.

 

[Shortround6]

Where did I say the P-47 took multiple 88mm hits???

Post #33 "I can come back with many pics of P-47's and B-17's with up to multiple 88mm hits and say if an 88mm cant kill it then how can a 20mm?

It can be take several ways.

Just for kicks appear to be P-47 took a 88mm hit. Too much damage for a 37 mm.

Just for kicks can you point out WHERE the 88mm projectile hit?
Not Fragments from the 88mm shell?

Appears to be artillery related, and the Germans used PETN anyway not sure of the Russian, Japaneese or US.

Rather missed the point didn't you.

Point being that you can control the fragments from a plain shell body somewhat by picking and choosing WHICH explosive is matched to WHAT shell body material without going to the trouble of trying to use a pre-fragmented shell.

Of course we can disregard the principal because it is land artillery and not aircraft shells?

 

[Glider]

OTOH a .50 will keep going until it goes through or hits something hard. So a rough comparison is a bunch of lines representing the .50 trajectory's going through the plane until it hits something. This in comparison to the 20mm HE which has spheres of influence where they blow up and then a couple lines from the fragments randomly expanded form the sphere. Those are the basic damage models that need to be compared, very difficult withe limited data to date.

OTOH a .50 must hit something to do damage or it goes straight through, whereas the 20mm as your evidence points out doesn't and that is the critical difference

 

[Ivan1GFP]

OTOH a .50 must hit something to do damage or it goes straight through, whereas the 20mm as your evidence points out doesn't and that is the critical difference

With what you just stated, does it make sense that additional kinetic energy / momentum adds substantially to the damage caused by an explosive shell? I believe it should not give any extra credit.

- Ivan.

 

[Shortround6]

Very few of these guns fired only one type of projectile in combat. Most combatants used mixed belts with varying percentages of different types of ammo, often 3 different types. British with .303 fighter guns tended to load all one type per gun but load different guns with the different types of ammo. US and perhaps the Soviets loaded their 12.7mm guns with a single type of ammo once they had an acceptable armor piercing incendiary.

The 20mm guns had the potential to act either way and since a belt of ammo routinely contained both HE and some form of AP or semi AP ammo the additional kinetic energy / momentum cannot be totally discounted either.

 

[zjtins]

P-47's and B-17's with up to multiple 88mm

right UP to to multiple hits maybe my grammar could have been better.

 

[zjtins]

Point being that you can control the fragments from a plain shell body somewhat by picking and choosing WHICH explosive is matched to WHAT shell body material without going to the trouble of trying to use a pre-fragmented shell.

ok prove it

 

[zjtins]

OTOH a .50 must hit something to do damage or it goes straight through, whereas the 20mm as your evidence points out doesn't and that is the critical difference

so both bullets travel essentially straight line until they hit something.

The HE give you a sphere of influence at he end the .50 cal does not. But the 20mm stop at the surface or just under while the .50 cal keep going until it hit something hard and destroys it. Is that clear now?

 

[zjtins]

With what you just stated, does it make sense that additional kinetic energy / momentum adds substantially to the damage caused by an explosive shell? I believe it should not give any extra credit.

Yes it does but the velocity of the fragments vs round, I do not see any evidence of that bullet speed adding any destructiveness to an HE shell .

 

[zjtins]

Point being that you can control the fragments from a plain shell body somewhat by picking and choosing WHICH explosive is matched to WHAT shell body material without going to the trouble of trying to use a pre-fragmented shell.

Of course we can disregard the principal because it is land artillery and not aircraft shells?

Land shells have a much, much higher HE to body weight ratio and they are cast. From looking at 200mm damage vs 88mm damage you can see a difference. The 20mm does not appear to have much shrapnel, the 88mm can have quite a bit of shrapnel (or appears to). But its hard to tell how much is 88 casing and how much is molten Al from the plane just making scars.

I cant find any reference showing testing for shrapnel affects.

 

[zjtins]

Very few of these guns fired only one type of projectile in combat. Most combatants used mixed belts with varying percentages of different types of ammo, often 3 different types. British with .303 fighter guns tended to load all one type per gun but load different guns with the different types of ammo. US and perhaps the Soviets loaded their 12.7mm guns with a single type of ammo once they had an acceptable armor piercing incendiary.

The 20mm guns had the potential to act either way and since a belt of ammo routinely contained both HE and some form of AP or semi AP ammo the additional kinetic energy / momentum cannot be totally discounted either.

Agreed but the ratio is important and the mere fact of having an AP 20mm in addition to the HE in the same belt means they found the HE alone lacking.

 

[zjtins]

Almost all the Spits with 20mm had 2 so around 1600 rpm so about 28 RPS
6x.50 cal=80, 8x5.50cal=107
If 4 rounds of 20mm hit the enemy from a 1 seconds burst, the for the same situation 6x.60= 11 rounds hit, 8x.50 15 rounds hit.
So the only time a 20mm might bring a plane down and the .50 would not is skin only impacts. you would have to look e at attack angle vs internal critical components. And also look at the type so attack that were carried out. The preferred method from being and slightly below or above. That attack method leaves little skin only target orientation.

 

[Shortround6]

ok prove it

I did, you just don't understand it.

Land shells have a much, much higher HE to body weight ratio and they are cast.

This is getting comical.
Land artillery shells usually have 7-15% of their weight in HE. Ideal would be more but you have to have a certain amount of strength in the shell walls.
Aircraft 20mm shells varied from 3.2 to 22% He to shell weight. The Extremes were both German, 20MM Hispano were around 8-8.7%
German WW II 105mm howitzer shell contained 9.3%
German 88mm Flak shell contained contained 9.3%

Most nations gave up cast shells in WW I. A few dozen (or few hundred) guns and gunners lost due to premature explosions in the bore because of substandard shells. Turning and boring shells out of bar stock was also given up.
The vast majority of large WW II shells were forged, what may be done with 1960-70 metallurgy may be a different thing.

"Agreed but the ratio is important and the mere fact of having an AP 20mm in addition to the HE in the same belt means they found the HE alone lacking.

And what should we make of the fact that most .50 cal belts until late 1943/early 1944 were 40% AP-40% incendiary and 20% tracer with tracer fading out near the end? That they found the .50 cal AP lacking?

No one bullet/projectile is the best at all things.

BTW A British 20mm SAPI will deliver just under 10 grams of incendiary material to BEHIND a piece of armor that a .50 cal AP can just barely penetrate, but I guess such a round would just bounce off an engine that a single .50 hit would destroy, right?

 

[Glider]

so both bullets travel essentially straight line until they hit something.

The HE give you a sphere of influence at he end the .50 cal does not. But the 20mm stop at the surface or just under while the .50 cal keep going until it hit something hard and destroys it. Is that clear now?

No. The RAF 20mm shell had a delay so it went off after penetrating the skin of the aircraft. As a result the 20mm didn't have to hit anything it would go off automatically.

If you want proof that this can happen, have a look at the Jap 20mm that did all that damage to the B24. it didn't hit anything hard but did a lot of damage. The RAF were not the only people with delayed action fuses

Is that clear now?

 

[Jabberwocky]

Agreed but the ratio is important and the mere fact of having an AP 20mm in addition to the HE in the same belt means they found the HE alone lacking.

Actually, they found 20 mm ball to be inadequate, that's why they replaced it with AP or SAP/I. HE stayed as it was: 50% of the belt.

 

[zjtins]

Quote Originally Posted by zjtins View Post
ok prove it ...I did, you just don't understand it.

You made a statement about a capability with no proof.

BTW A British 20mm SAPI will deliver just under 10 grams of incendiary material to BEHIND a piece of armor that a .50 cal AP can just barely penetrate, but I guess such a round would just bounce off an engine that a single .50 hit would destroy, right?

So your own evidence admit the original HE round was not sufficient. So that it had to carry multiple round including the chance of any one round actually doing damage to the particular target it was design for. An HE hitting and engine is not effective enough to the point they added AP round. This also meant an AP round going through a soft target acts like a .50 cal and just make a hole. So the average number of rounds needed increases, but the effectiveness of a single hit may go up.

I just realized you just talk about the Brits what about the Germans, Russian, Japanese and yes even the Americans, Italians ...?
Just the Brits should be less than 10% of all A-A and roughly 40%-50% of those would be .30 cal only.
the Russians used 10 different shells have no idea of the distribution.
Same for the rest. The Germans appears to have leaned towards the higher HE content with some form a of minegeshoss regardless of caliber especially as they went after bombers.
From what little info I can find the Japanese seemed to also go that way.

Actually, they found 20 mm ball to be inadequate, that's why they replaced it with AP or SAP/I. HE stayed as it was: 50% of the belt.

The ball is an American term. I dont remember seeing any German, Russian 15mm on up having lead as a main substance, they were all hard metals or HE or combinations or other. The exception was use of lead to create the vehicle for a tracer bullet.