What was the air to air weapon, or combination of weapons, used in WWII?

[Jabberwocky]

The reliability issue does raise a question for me that I know virtually nothing about. How did the 20mm, in its most common guises (Brit, Russian, German Japanese and US) compare in terms of relaiability (resistance to jams) to the 50 cal. We used 50 cals on the back of our patrol vessels, and their relaiability was legendary. They never gave us problems. How did they compare to the various types of 20mm weapon? why was the US early attempts at a 20mm weapon given such a poor report as to relaiability. was it htat bad, or were the Americans simply too entrenched at the time in their belief in the M2.

I've found a couple of pieces of information on stoppage rates for the M2 and Hispano

In US service (Based on 8th AF over first 8 months of 1944)

Hispano: 1 per 505 rounds (P-38 only)
M2 Browning: 1 per 1442 rounds (P-51, P-38, P-47)

In the MTO:
M2 Browning: 1 per 1300 rounds in 1942, 1 per 1700 rounds (P-40s in Tunisia, not period given)

In RAF service:

Hispano: 1 per 1500 rounds

D-Day to end of hostilities:

Hispano: 1 per 1560 rounds
M2 Browning: 1 per 3300 rounds

In RAAF service:

Hispano: 1 per 240 rounds (over Darwin, Spitfire Mk Vc with incorrely manufactured gun heating systems and) improving to 1 per 400-500 rounds later in conflict
1 per 1545 rounds (Spitfire VIII);

In RNZAF service:

1 per 600-750 rounds (Beaufighters, drum feed)

 

[parsifal]

Thats very interesting. There is a bit of spread for the 20mm but for the RAF and cW, when installed correctly (ie, Darwin Wing excepted), there isnt a lot of difference in reliability.

I always believe that the 20mm was a weapon with much greater firepower that the 12.7mm weapon. I believed there was a reliability issue for the 20mm, but on the basis of that information, it does not appear to be the case.

And no, Im not going to say "prove it". I believe you guys

 

[nincomp]

Parsifal,
Your impression of the 20mm being less reliable in WWII service with the USA is not wrong. On the other hand, the British had better luck with it.
There is an article on this subject on Anthony Williams "Cannon, Machine Guns, and Ammunition" site that discusses the 20mm aircraft gun in US service:
The Hispano-Suiza HS.404 20 mm Aircraft Gun in US Service

There are articles on WWII fighter armament as well as William's discussion of the "ideal WWII fighter armament" on this site. These articles have been brought up on this forum before, but the website is well worth a visit.
CANNON, MACHINE GUNS AND AMMUNITION

I hope that those links work (they sure look screwy on my screen).

 

[nincomp]

Earlier in this thread, someone asked how many .50 caliber bullet hits it took to bring down an opposing aircraft.
Looking at this gun-camera footage (posted by Janisch in another thread), it appears the answer may be "sometimes, quite a few hits were needed."


View: https://www.youtube.com/watch?v=La3qJ4sptuE

 

[zjtins]

Sorry but quite a few its not quantified nor does it tell the whole story.

In the BoB the Brits used 1/2 to full ammo load to drop 1 German fighter. It worked by they were not happy.

Against Japan the US (once tactics were created to fight the superior maneuverability), less than 1/2 second burst on target brought down Japanese fighters (typically), I posted a youtube video earlier showing this.

Also you posted a video one with many off angle shots meaning many shots flat out missed, you can see the same for the German 20mm fighters having the same problem with off angle, the 20mm offered no aiming advantage.

If you count actual hits into the engine, pilot, or fuel tank the plane shows obvious damage or is killed.
Same goes for 20mm but it also can cause skin damage much faster which can affect airflow and reduce performance to where a second shot becomes a real probability but I argue a reduced likelihood for engine or armor penetration




View: https://www.youtube.com/watch?v=iyJAlsJAbZw

Take a look a the infamous B-17 attack by a Bf-110 G-2. Be careful it says BF-110 G2 but the field kit could be 2x20mm and 2x30mm not 4x8mm.

Lots of misses and at the end both ball turret and rear gunner appear dead but the 4 engines are rotating.

 

[CobberKane]

Earlier in this thread, someone asked how many .50 caliber bullet hits it took to bring down an opposing aircraft.

View: https://www.youtube.com/watch?v=La3qJ4sptuE

I've often wondered about this. The only study I know of concerning the effectiveness of armament was the By the Germans, who examined the wreckage of downed B-17s and concluded that on average it took twenty 20mm hits to bring one down. They concluded that only two percent of rounds fired in the air actually hit a bomber, ergo the average pilot would have to fire 1000 rounds of 20mm ammo to bring down a bomber - more than the ammo load of any LW single engine fighter.This information was part of the impetus towards the 30mm cannon, which required on average three hits to do the job.
The USN considered one 20mm to be equal to three .50s. The previously mentioned blog calculates 3.3 .50s. Going with the USN figure, that means it would take about 60 .50 hits to down a heavy bomber, which seems reasonable. That would require the expenditure of 3000 rounds, again more than the ammo load of any WWII fighter.
When used against fighters, I've heard the figures of 10-15 .50 hits to bring down an enemy aircraft, which should be about equivalent to 3 - 5 cannon hits. Using the same accuracy figures that the LW arrived at vs heavy bombers (a stretch, but I don't have anything else) that would require the expenditure of 500-750 rounds of .50, which would be about seven to ten seconds of fire for a fighter with six guns, which again sounds reasonable to me.
I realise I'm making pretty casual use of the data here. I'm happy with the three to one ratio for HMGs to 20mm, coming as it does from the USN and likewise the figures provided by the LW. Extrapolating from bomber intercept to fighte engagements is pushing things, but having said that the results seem pretty consistent with what I've read in combat reports and the like. If anyone has more hard data on what was required to knock down a fighter I'd love to hear it.

 

[drgondog]

It has been gone over many times.

Basically the .50 Browning was more reliable than the either the Hispano or Oerlikon guns. One question is how many or what rate of stoppage is acceptable. one stoppage per gun every 3-5 flights on which the ammo bins are totally emptied or do you NEED 5-7 flights or????

The Americans screwed up in two ways.
1. They classified the 20mm as a cannon and not as a small arm or machine-gun. In US ordnance terms this meant that there was a bigger + / - tolerance allowed on the parts than would be allowed on a Machine gun's parts. This took quite a while to sort out.
2. They were working from original French drawings. The chamber was a bit longer than it should have been and this lead to light primer strikes. The British had already shortened the the chamber and got much better reliability but for some reason the US Ordnance dept refused to listen.

Shortround - I'm confused. Didin't the 20mm headspace to a shoulder datum line as it was a rimless/beltless cartridge like the .50 caliber? If so then there should not have been a problem with a longer leade - or conversely with a headspace problem due to a longer chamber - there would been Huge problems - more than just soft strikes on the primer.
US 20mm ammunition manufacturers were not happy as production batches of ammo would fail in US guns and yet work fine in a British gun.

There is also the question of greased or wax coated ammunition.

See: Modifications and Attempts at Standardization

Educate me on this?

 

[Shortround6]

I believe the the Chamber was about 1mm too long, Which on case of this size is enough to screw up functioning but not enough to be dangerous.

If you have ever seen what a .303 case looks like before it it fired in some guns and what it looks like when it comes out you would see their is quite a bit of "extra" room in a .303 chamber

Since it headspaces on the rim there is no problem with the firing pin pushing the cartridge forward.

With the rimless cartridge, you are correct, it should have depended on the shoulder of the cartridge case hitting the shoulder of the chamber to position the case for the firing pin hit. But you do need a bit of tolerance. I have seen M-1s and M-14s where somebody got a little to aggressive with the reloading die show the same sort of behavior and it is why the armorers had headspace gauges, go, no go and field. The danger of case rupture is present but is rare unless head space gets way out of wack with brass OF GOOD QUALITY. Poor brass (brittle) will not stretch much before cracking.
Some guns will fire a fair amount of the time with the extractor holding the case against the bolt face but this is not how they are designed and a "fair amount of the time" gets used up pretty quick in a machine gun (one failure in a hundred rounds?).

During WW II there were three grades of .30 cal ammo. 1st was aircraft machine gun grade, 2nd was ground machine gun grade and 3rd was rifle. The grading was done by brass quality and dimensions for functioning, not accuracy. Rifles got the "junk" as it was the least critical use. Aircraft machine guns being hard to "un-jam" in flight and a ground machine gun that jammed took out a bigger proportion of the ground units fire power than a jammed rifle.

The 1mm too long chamber was just enough to screw up the reliability without be too dangerous. If you had the long chamber AND a manufacturing 'lot' of poor brass (either material or heat treat/anneal) you could wind up with split shoulders.

The firing pin is pushing the entire cartridge forward in the chamber until it hits the shoulder and this cushions the blow to the primer. Not all primers had the same sensitivity.

I hope this helps.

 

[Jabberwocky]

Sorry but quite a few its not quantified nor does it tell the whole story.

In the BoB the Brits used 1/2 to full ammo load to drop 1 German fighter.

You've got proof of this, I assume. Written, video or visual?

Archie McKeller would be surprised, given that he managed to down four Bf-109s in a single flight. He also claimed three He-111s on one flight, and three He-111s and a Bf-109 on another.

Yes against German bombers, once they were armoured and had self sealing fuel tanks, the .303 generally proved inaequate. There are stories of 3 or more fighters dumping entire ammunition loads of .303 into He-111s and having the aircraft remain in the air. Of course, how many rounds were hitting will never be clear.

Against fighters, even armoured fighters, not so much. A solid burst of 1-2 seconds was generally enough to bring them down, provided the pilot hit his target.

Against Japan the US (once tactics were created to fight the superior maneuverability), less than 1/2 second burst on target brought down Japanese fighters (typically), I posted a youtube video earlier showing this.

So you're comparing unarmoured Japanese fighters, of generally light construction and without self-sealing fuel tanks against German fighters with armour and self-sealing tanks, as your 'evidence'?

 

[tyrodtom]

Sorry but quite a few its not quantified nor does it tell the whole story.

In the BoB the Brits used 1/2 to full ammo load to drop 1 German fighter. It worked by they were not happy.

Against Japan the US (once tactics were created to fight the superior maneuverability), less than 1/2 second burst on target brought down Japanese fighters (typically), I posted a youtube video earlier showing this.

Also you posted a video one with many off angle shots meaning many shots flat out missed, you can see the same for the German 20mm fighters having the same problem with off angle, the 20mm offered no aiming advantage.

If you count actual hits into the engine, pilot, or fuel tank the plane shows obvious damage or is killed.
Same goes for 20mm but it also can cause skin damage much faster which can affect airflow and reduce performance to where a second shot becomes a real probability but I argue a reduced likelihood for engine or armor penetration




View: https://www.youtube.com/watch?v=iyJAlsJAbZw

Take a look a the infamous B-17 attack by a Bf-110 G-2. Be careful it says BF-110 G2 but the field kit could be 2x20mm and 2x30mm not 4x8mm.

Lots of misses and at the end both ball turret and rear gunner appear dead but the 4 engines are rotating.

How can you judge how long the burst of fire is from a gun camera film ?

They're silent, plus you have no ideal if you're seeing the whole fight sequence, and some are in slow motion.
If there's gun firing sounds in the videos, it was dubbed in late.

 

[buffnut453]

I was under the impression that most gun camera installations were configured to operate the camera when the gun trigger activated so the film only captures periods when the guns were being fired.

 

[Greyman]

Early war British gun cameras only exposed when the guns were fired. Later there was a delay after the guns were fired so that the effects could actually be viewed. This seems to be how American and German gun cameras operated as well.

Generally aircraft with gun cameras also had a separate control with which to use the camera only, without the guns.

 

[zjtins]

Generally aircraft with gun cameras also had a separate control with which to use the camera only, without the guns.

True not sure when and who all did this but remember camera footage was also used for intelligence of new types not just to confirm kills.

 

[zjtins]

I am using the gun camera footage plus the books I have read discussing the actual shoot downs. Not all but from what I have read for a US fighter if on target, 1/2 second has been described as all that 's needed (for a fighter). I am sure it the same for 20mm 4x guns. But having read accounts of the BoB with 8x .303, they generally describe as hosing it down until fire or loss of control occurs. Again this seems to match the gun camera footage from that era. I cannot find a definitive analysis by anyone, only test plates and estimates. So again if someone has a reference would love to see it.

Also note few accounts of either BF109E or Spit II, V with multiple shoot downs yet the US and FW-190 have far more documented. Again rates are hard to come by but between the gun camera footage and pilot commontary seems about right.

 

[zjtins]

So you're comparing unarmoured Japanese fighters, of generally light construction and without self-sealing fuel tanks against German fighters with armour and self-sealing tanks, as your 'evidence'?

But they compare a large portion of US combat. To ignore them is to say it did not happen.

 

[zjtins]

How can you judge how long the burst of fire is from a gun camera film ?

They're silent, plus you have no ideal if you're seeing the whole fight sequence, and some are in slow motion.
If there's gun firing sounds in the videos, it was dubbed in late.

Throw out the footage of dubious length and you are still left with clear start end sequences. Knowing they use some fraction of tracers you can count them for length of time.

 

[zjtins]

They concluded that only two percent of rounds fired in the air actually hit a bomber, ergo the average pilot would have to fire 1000 rounds of 20mm ammo to bring down a bomber - more than the ammo load of any LW single engine fighter.This information was part of the impetus towards the 30mm cannon, which required on average three hits to do the job.
The USN considered one 20mm to be equal to three .50s. The previously mentioned blog calculates 3.3 .50s. Going with the USN figure, that means it would take about 60 .50 hits to down a heavy bomber, which seems reasonable. That would require the expenditure of 3000 rounds, again more than the ammo load of any WWII fighter.
When used against fighters, I've heard the figures of 10-15 .50 hits to bring down an enemy aircraft, which should be about equivalent to 3 - 5 cannon hits. Using the same accuracy figures that the LW arrived at vs heavy bombers (a stretch, but I don't have anything else) that would require the expenditure of 500-750 rounds of .50, which would be about seven to ten seconds of fire for a fighter with six guns, which again sounds reasonable to me.

IMHO you are extrapolating which can lead to mistakes.
The ME-109 did not carry 1000 rounds of 20mm even without board guns the FW-190 barely. Yet B-17 were shot down and some Germans shot down more that 1 B-17 in a fight (ever after war records showed this).

I suggest this was because novice pilots missed and good pilots did not miss so much. So the average 2% hit rate is to me very misleading. Some of the German videos show many rounds hitting.

To extrapolate to a .50 cal round on equal terms I believe leads to a false conclusion. The variables are not sufficiently related to make that comparison.

 

[Shortround6]

You may also have to take into account ammunition used. The British tended not to mix belts of machine gun ammo but instead loaded different guns with different ammo on fighters, a common load out in The BoB was 3 guns loaded with ball (lead core) , 2 guns with AP (hardened steel core), two guns with MK IV incendiary/tracer and one gun loaded with MK VI Incendiary ( De Wilde). Later in the war Spitfires and Mosquitoes had 2 guns loaded with AP and two guns loaded with the MK VI incendiary. The MK IV incendiary was about twice as effective in setting fuel tanks on fire as the MK IV incendiary/tracer.

In many cases during the BoB the guns were set to converge too far away and the pilots were firing from waaay to far away leading to a lot fewer hits per 100 or 1000 rounds fired. British doctrine also called for a deliberate miss-alignment of the guns at times in order to give a better chance of scoring SOME hits but it means that it was a lot harder to get all eight guns hitting at the same time.

The other problem is keeping the guns on target for even 1/2 second. at 300mph the target will move 220 ft in 1/2 second and the firing plane, if doing 300mph, will also cover 220ft in the 1/2 second. The bullet "stream" may go on and off the target several times even in just 1/2 a second. From other angles and for othr targets the bulet stream may stay on the target for much more than 1/2 second.

I am not trying to say the eight .303 gun armament was all that was needed, it wasn't, but unless you know some of the other factors going on at the times the gun camera footage was taken it is hard to evaluate the gun camera footage on it's own.

US .50 cal guns changed ammo types and ammo mixes in the belts as the war went on so trying to compare gun camera footage from 1942 to 1944 should take that into account.

 

[Jabberwocky]

But they compare a large portion of US combat. To ignore them is to say it did not happen.

That's not what you were doing though.

You were specifically comparing the firing times of .303 armament in the Battle of Britain - firing on armoured German fighters with self sealing tanks - against the .50 cal armament firing on unarmoured Japanese fighters without self sealing tanks. And, you were doing it with your own questionable estimations of "1/2 to full ammo load to drop 1 German fighter" and "less than 1/2 second burst on target brought down Japanese fighters (typically)"

Yet, you admit that you've nothing to go on but youtube videos of gun camera footage highlights, which neither know the speed of or which aircraft were doing the firing.

Do some more research (like, the US national records office and the UK national archives) before making hard conclusions.

 

[CobberKane]

IMHO you are extrapolating which can lead to mistakes.
The ME-109 did not carry 1000 rounds of 20mm even without board guns the FW-190 barely. Yet B-17 were shot down and some Germans shot down more that 1 B-17 in a fight (ever after war records showed this).

I suggest this was because novice pilots missed and good pilots did not miss so much. So the average 2% hit rate is to me very misleading. Some of the German videos show many rounds hitting.

To extrapolate to a .50 cal round on equal terms I believe leads to a false conclusion. The variables are not sufficiently related to make that comparison.

The two percent figure the LW came up with was arrived at by examining downed bombers and gun camera footage - all of it, not the juicy tidbits we get off the net today. They assumedly would have looked at both the footage from experienced pilots, who as you say undoubtedly scored much higher hit rates, to novices who may have blazed away without hitting anything at all. Their intention was to determine the percentage of rounds fired by their fighter force as a body, not specifically the hit rates of experts or novices, because they wanted to reach conclusions about how the average pilot performed and whether he had the armament to do the job. Adolf Galland the actual pilot may not have needed more guns than his Bf 109 had to reliably knock down a B-17 but Johan Schmitz, the statistically constructed average pilot, did, and he was the guy you needed to cater for.
German pilots did shoot down multiple B-17s, which suggests to me one of two things: either they were experts who were scoring considerably more hits than the average pilot could expect too, or (less likely but it undoubtedly occurred) they were less than expert pilots who got lucky.
I agree that I am largely speculating with my figures for the .50, although I am at least extrapolating from the basis of the LW study and the USN standard that one 20mm equals three .50 in firepower. I don't recall where I got the figure of 10-15 hitsbeing typically sufficient to down a single engine fighter (and it may have been referring to the PTO) but the 7-10 seconds of fire seems about right, for what that's worth.
So, as I said I'd love to see some direct studies of the effects of .50 cal fire, but lacking that all I can do is work with the USN and LW stuff. Not perfect, but then again some people maintain that HMGs alone should have been fine for tackling heavy bombers and the like, and I've never seen ANY evidence for that.