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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 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.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
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
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.
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.
How can you judge how long the burst of fire is from a gun camera film ?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.
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.Generally aircraft with gun cameras also had a separate control with which to use the camera only, without the guns.
But they compare a large portion of US combat. To ignore them is to say it did not happen.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'?
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.
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.
But they compare a large portion of US combat. To ignore them is to say it did not happen.
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.