.50 cal machine guns vs 20 mm autocannons on US aircraft (1 Viewer)

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Let's not berate Charles, he was a well respected engineer and pilot, recommending engine leaning techniques for the P-38 increasing their endurance. He also flew missions with the Marines as quoted in America's Hundred Thousand,
May, '44- Charles Lindbergh starts flying missions in the Corsair with USMC pilots at Green Island and Emirau in the Pacific. His last missions with an F4U-(sic) in the area will be to Rabaul on the ninth of June".
Wikipedia also stated he taught the Marine pilots how to takeoff with a greater load.
 
I understand what you are saying but kinetic energy is also part of the energy equation and cannot be dismissed lightly.

Of course KE is an important part of the equation, but seems that chemical energy was more worthwhile*, for same armament ammo weight cost - hence the preference for cannons in most of the major air forces of WW2.

*if that was not so, all the Hispanos, MG 151s and Shvaks would've been firing AP/API/ball ammo all the way, not predominantly HE/HEI as they did historically. And USN wouldn't be bothering with HE/HEI for their 20mm, but would've used the AP/API/ball ammo there.

I said this poorly "replace the 50 in the Navy, whose tech staff did prefer it and did update after the war". I meant to say that the tech staff preferred upgrading the 50 to 20 mm and did update after the war.

Okay, thanks for the explanation.

Oct. '44, some of the most vicious and deadly fighting using these "left over aircraft" was yet ahead for the allied forces in the Pacific, and the Navy was about to field the most powerful fighter it would field in the war, the F4U-4, with 50s.

As the 'left-overs', I was pointing out at the WW2 planes/designs that were updated/upgraded post-war.

With the F4U-4C it tried out the American gun, I think, and it was a failure. The Post war F4U-5 also came with 20mm, but I don't know which one.

Again, the US cannon soap-opera was to blame, not the cannons as a whole.

I was not complaining about the jamming sensitivity of the 20s. I was comparing six 50s to two 20s. With one gun jam, the six 50s only lose a sixth of its fire power, the 20s, however, lose half.

Any plane that was capable to carry 6 HMGs, was also capable to carry 4 cannons. Thus mitigating the effect of a cannon that jammed.
 
I agree and I must admit that I lack any knowledge of impact of explosive shells.

Since the effect of the exploding shells IS a large part of their advantage disregarding it seems to be stacking things to favor the kinetic energy based .50 cal round.

Maybe at BuAer, but I have not read anything about desire at ops, even at the Fighter Conference. Of course the Navy was fighting Japanese aircraft that were notoriously vulnerable to 50 cal fire.

Basing your future needs on what your enemy has fielded in the past is not good planning. If the Japanese had been able to shift production to more Franks, Tony's Georges, and Jacks and fewer Oscars and Zekes in the last 2 years of the of the war the opinion of the .50 might have changed a bit. Granted they are not bullet proof but planning on your opponent NOT to fit armor or better self-sealing tanks one-two years in the future?

I fully understand the Navy was moving toward the 20mm. However, to be picky, the FH-1 Phantom initial production contract was placed on 7 March, 1945, with four (!) 50 cals.

True, you got me.
But considering that the McDonnell F2H Banshee Mock-up was completed within a month of the " FH-1 Phantom initial production contract" (and only production contract of 100 planes) one has to wonder just serious the Navy was about the FH-1 Phantom whose design dates back almost two years. Initial design work for the Banshee had to be going on for a number months before the contract for the FH-1 Phantom was placed. Phantom may have been intended for what it turned out to be, a way to give both McDonnell and the Navy experience with jet aircraft (and McDonnell experience in producing aircraft, this being their first production plane) much like the Army P-43 contracts or P-59 contracts.


I have never stated that the Navy did no plan to go to the 20mm, only that there was no urgency to do so because the weapons they had were effective. It is intuitively obvious that both the Navy and the AAF were interested in more firepower, aren't they always, but both apparently felt disrupting the prosecution of the war to upgrade their armament was counter productive. The Navy chose the 20 mm to upgrade firepower, the AAF the M3 50 cal. for their fighters. Both were effective through the Korean War. The post Korean War upgrades in rate of fire of the 20s made the next upgrade a mute point.

Claiming the M3 50 cal was effective in Korea is dubious. Yes it shot Migs so it wasn't totally ineffective but it finally got through to the Air Force that something better was needed. The Air Force was already using 20mm cannon on Bomber interceptors when weight allowed ( early F-94s being a little weight limited).
 
I believe that the F8F was originally designed and produced with four 50s.

Lindberg did many more tasks with the AAF, USN and private industry during and prior to WW2. He is said to have flown every major model of AC built during WW2 including the 4 engined bombers. He had a major role in the development of the Corsair, P47 and others. He instructed pilots in the Pacific, including the P38, on how to maximise range. He delivered a 4000 pound bomb load from a Corsair on a Japanese target. He and Boone Guyton, chief test pilot on the Corsair, became very close during the war years.
 
Since the effect of the exploding shells IS a large part of their advantage disregarding it seems to be stacking things to favor the kinetic energy based .50 cal round.

I was not disregarding explosive shell energy. I just have no way to judge the impact. The only hint I have is from the book which states the 20 mm is equal to three 50s, but the kinetic energy at 500 yards is equal to two and a half 50s. The difference must be the explosive effects. I used for three to one for comparison.

Basing your future needs on what your enemy has fielded in the past is not good planning. If the Japanese had been able to shift production to more Franks, Tony's Georges, and Jacks and fewer Oscars and Zekes in the last 2 years of the of the war the opinion of the .50 might have changed a bit. Granted they are not bullet proof but planning on your opponent NOT to fit armor or better self-sealing tanks one-two years in the future?

The statement here was that, for the most part, the Navy was fighting against softer Japanese aircraft that were more susceptible to 50cal fire than were their German counterparts and thus, at the ops level, saw less of a need for the 20s, therefore not much of a push to implement them.

True, you got me.
But considering that the McDonnell F2H Banshee Mock-up was completed within a month of the " FH-1 Phantom initial production contract" (and only production contract of 100 planes) one has to wonder just serious the Navy was about the FH-1 Phantom whose design dates back almost two years. Initial design work for the Banshee had to be going on for a number months before the contract for the FH-1 Phantom was placed. Phantom may have been intended for what it turned out to be, a way to give both McDonnell and the Navy experience with jet aircraft (and McDonnell experience in producing aircraft, this being their first production plane) much like the Army P-43 contracts or P-59 contracts.

I think this is a stretch. In April '45, the F2H was three and half years away from ops and depended on an engine that was not even developed, and, in this time period of many failed engine designs, would have been high risk. As for the small number of initial contract orders for the Phantom, I think war purchase mentality was starting to wind down at this time, and its final production number, 60, was almost equal to the initial order for the Banshee at 56. The FH-1 was as fast as the F4U-5, with much more potential. I have no doubt that the Navy designed, purchased and fully expected the FH to be its front line jet fighter until and if the Banshee became available, just as the AAF expected the P-59 to be its front line jet fighter. The P-59 only became a test and training aircraft after its performance failed miserably, it was 60 mph slower than the FH-1.

Inclusion of the four 50s on the production FH indicates a couple of things. One, the Navy felt that the centerline mounted four 50s were equivalent to six wing mounted guns and, second, the 50s were acceptable as armament for a fighter, maybe marginally so, but undeniably acceptable. Weight may have been an issue but the Navy knew two 20s would offer better firepower. Maybe reliability was an issue.

Claiming the M3 50 cal was effective in Korea is dubious. Yes it shot Migs so it wasn't totally ineffective but it

Claiming the F-86 was marginally effective due to its armament seem dubious to me. I assume you have loads of comparison data comparing F-86 engagements against the Mig-15 vs. aircraft with 20mm showing that the efficiency of the 20s is so much better. The P-51 was prodigious killer of aircraft in WWII including a few Me-262s when they could catch them. I doubt that very few would say the 50cals in the P-51 were only marginally effective. To say that he F-86 against aircraft no more tough than the German fighters, with effectively twice, since the guns were centerline, the firepower of the P-51, is marginal seems illogical. Nothing succeeds like success and to argue something else is more efficient without one-to-one comparison of performance in the same environment is an empty argument, otherwise there are too many variables.

finally got through to the Air Force that something better was needed. The Air Force was already using 20mm cannon on Bomber interceptors when weight allowed ( early F-94s being a little weight limited).

The AF realized the 50 were so marginal they immediately installed them in the highly upgraded, and delayed, F-86F, no, wait, it had 50s. Surely it would have delivered the post war "fighter-bomber" version, the F-86H with 20s, well, no, they delivered the first group with 50s. Not until the much superior M-39 come along did they upgrade the "H" to 20s. No "marginal" desperation shown here.

Those bombers were slow non-maneuvering targets, and night bombers were difficult to target (low probability of hit per projectile?) and, yes, tougher.
 
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I was not disregarding explosive shell energy. I just have no way to judge the impact. The only hint I have is from the book which states the 20 mm is equal to three 50s, but the kinetic energy at 500 yards is equal to two and a half 50s. The difference must be the explosive effects. I used for three to one for comparison.

We do know that according to Tony Williams who has studied weapons for many years and published a number of books that the 0.5 rd had 0.86 gm of HE/I and the 20mm Hispano V/M3 rd had 11.35 gm of HE/I

In other words the 20mm had over 13 times the explosive content of the 0.5.

My posting 81 tried to add this to the hit probability calculations to show the overall impact on efficiency
 
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I was not disregarding explosive shell energy. I just have no way to judge the impact. The only hint I have is from the book which states the 20 mm is equal to three 50s, but the kinetic energy at 500 yards is equal to two and a half 50s. The difference must be the explosive effects. I used for three to one for comparison.

Try going to Tony Williams site. WORLD WAR 2 FIGHTER GUN EFFECTIVENESS

He figures that ONE 20mm round is 4.34 times more destructive and ONE .50 cal round. Because the .50 fires faster (13rps vs 10rps) the 20mm is about 3.33 times more destructive at the muzzle per gun. this doesn't take in to account hit probability so yes the 20mm is probably about 3 times as effective as the .50 cal.

I would note that the Germans, Italians and Japanese all developed HE rounds for their 12.7-13mm machine guns (even though capacity was usually 1-2 grams) so apparently they thought there was something to the exploding projectile idea.

The problem is one of weight. While six .50s can be an adequate battery or even an effective one in terms of damage done it is a heavy battery. A single 20mm round weighs about 257 grams to the a .50 cal rounds 112grams (depending on bullet).
even if the 20mm round is a non-exploding round each 20mm round has 2.82 times the muzzle energy. Throw in the weight of the links and it gets worse. 100rounds of 20mm ammo goes about 62.5lbs while 100rounds of .50 cal goes about 30-30.5lbs.

While six .50s are lighter than four 20mm guns by the time large amounts of .50 cal ammo are added the .50 cal battery winds up weighing more and offering less.


The statement here was that, for the most part, the Navy was fighting against softer Japanese aircraft that were more susceptible to 50cal fire than were their German counterparts and thus, at the ops level, saw less of a need for the 20s, therefore not much of a push to implement them.

At ops level you are rarely going to be able to replace the guns in existing aircraft, you can only request that the upcoming planes be fitted with better armament. Of course you need a more effective gun to be available and the Ordnance dept had screwed the pooch on that one. ops level doesn't usually issue the specifications for new aircraft.


I think this is a stretch. In April '45, the F2H was three and half years away from ops and depended on an engine that was not even developed, and, in this time period of many failed engine designs, would have been high risk.

This also a bit of a stretch, true the F2H was 3 1/2 years away from ops but what with the end of the war and the wind down the FH-1 was almost 2 1/2 years away from ops. This means the 20mm armed F2H was only about a year (or less) behind the .50cal armed FH-1 in timing. It also does nothing to show that the Navy was happy with the .50 cal armament since they were examining mockups of aircraft with 20mm cannon in the winter/spring of 1944/45.

Inclusion of the four 50s on the production FH indicates a couple of things. One, the Navy felt that the centerline mounted four 50s were equivalent to six wing mounted guns and, second, the 50s were acceptable as armament for a fighter, maybe marginally so, but undeniably acceptable. Weight may have been an issue but the Navy knew two 20s would offer better firepower. Maybe reliability was an issue.

Since design work on the FH-1 dates from 1943/44 it may indicate the Navy didn't want to delay the introduction and run up the costs of what they knew was an interim aircraft. With the war winding down the order was cut from 100 to 30 and then bumped back up to 60. Navy may have decided that four M3 .50cal guns equaled the fire power of 6 M2 .50cal guns and so could accept the four .50 armament (with it's lighter weight) for specialized aircraft like the FH-1 the Ryan Fireball and the first F8Fs.
Work on the F2H had started before the first FH-1 Prototype ever flew.

Claiming the F-86 was marginally effective due to its armament seem dubious to me. I assume you have loads of comparison data comparing F-86 engagements against the Mig-15 vs. aircraft with 20mm showing that the efficiency of the 20s is so much better.

No I don't but then I doubt you have loads of comparison data comparing F-86 engagements against the Mig-15 vs. aircraft with 20mm showing that the efficiency of the .50 is so close as to make little difference. We have accounts of Pilots getting Mig-s in their sights several times and getting hits each time (same aircraft) before the Mig goes down. We have accounts of Migs returning home with 40-50 .50 cal hits. they may have been flying junk but they made it.

The P-51 was prodigious killer of aircraft in WWII including a few Me-262s when they could catch them. I doubt that very few would say the 50cals in the P-51 were only marginally effective.

Here we go with the "if it worked it must be good" argument. we are also into the variables. Different rates of fire, different ammunition, and a few anecdotes.

To say that he F-86 against aircraft no more tough than the German fighters, with effectively twice, since the guns were centerline, the firepower of the P-51, is marginal seems illogical.

How do you know the Migs were no more tough than the German fighters? you do have structural analysis of the fighters showing strength of the various aircraft?
I will admit I don't have that information, but the Mig 15 weighed about 460lbs less than a Me 262 did empty, it had a slightly smaller wing and it's single engine weighed about 240lbs less than ONE of the engines on the Me 262. Without engines the Mig 15 is about 1500lbs heavier than a 262 and is a bit smaller. Germany plane "MUST" be just a sturdy due to "German engineering" right? The fact that the Mig could fly over 140mph faster has nothing to do with why it might have to be built just a bit stronger.

The bit about the center line guns needs a bit of thinking too, Center line guns may have a higher hit probability, they don't do a thing for the effectiveness of the hits that are obtained. Germans are the ones that figured that centerline guns were worth twice what wing mount guns were but then the Germans were usually mounting a mish-mash of guns with different trajectories and times of flight. A lot of the early German wing mount guns had additional problems.
Nothing succeeds like success and to argue something else is more efficient without one-to-one comparison of performance in the same environment is an empty argument, otherwise there are too many variables.

you are right, nothing "succeeds like success" and thinking like that kept the smooth bore musket and cannon in use for decades ( if was good enough for Wellington at Waterloo.......) and was the rallying cry for every Colonel Blimp in many armies/countries for 150 years (or longer). It kept the bolt action repeating rifle in use in most countries during WW II (if was good enough in WW I........) by the most armies realized they needed to change it was too late.
While battlefield input is good it has too many variables to give a really accurate picture of weapons performance ( was that tank at 30 degrees or 40 degrees when the projectile hit? 800 yds or 900yds? measured not guessed). It can confirm or contradict range testing but trying to get reproducible results is a bit a difficult.
It is also usually just a bit late for weapons development too. Most aircraft guns took 4-6 years for "new guns" (some longer) to go from drawings to service weapons. Waiting until your current weapon/s aren't working (succeeding) to tool-up, manufacture, issue and combat test new weapons (even if already designed and range tested) can leave you behind the curve.


The AF realized the 50 were so marginal they immediately installed them in the highly upgraded, and delayed, F-86F, no, wait, it had 50s. Surely it would have delivered the post war "fighter-bomber" version, the F-86H with 20s, well, no, they delivered the first group with 50s. Not until the much superior M-39 come along did they upgrade the "H" to 20s. No "marginal" desperation shown here.

You are correct, no desperation shown there. Stupidity yes. Or is it the "Nothing succeeds like success" syndrome and believing their own kill/loss ratio claims at the time? Or admitting the Navy was right? :)
Those bombers were slow non-maneuvering targets, and night bombers were difficult to target (low probability of hit per projectile?) and, yes, tougher.

Lets follow the logic here, 20mm guns are better for "difficult to target (low probability of hit per projectile?)" that were fleeting in nature, try and get a second firing pass on the same target with a night fighter, and tougher targets yet the 20mm guns were not good for daylight targets that were easier to target and while quicker in motion could usually be followed better both before and after the firing period. And the fighter targets required fewer hits to down.
 
Seems to me that the AAF argument that the more guns in the 50BMG equipped AC and the more ammo carried enabled the average gunner a better chance to get hits makes some sense. The US AC that carried the 50BMGs probably carried around twice as much ammo per gun as would have been carried if they had been equipped with 20 MMs and they would usually carry two more guns. No doubt the 20 mm round is more lethal but the 50BMG would be more capable of getting hits because of higher rate of fire, more guns and ammo and somewhat better ballistic properties ( flatter shooting and higher down range velocities.)

An analogy to me which might apply is two gunners of equal ability going dove hunting. The limit is ten birds and one gunner is armed with a twelve gauge and has ten shells with his choice of shot size, probably 7.5 or 8. The other hunter has a 20 gauge with 20 shells, probably 7.5. No question the 12 gauge is more lethal on doves but the 20 gauge is adequate. I have done lots of dove hunting and have both size shotguns. My bet is that the guy with a 20 gauge and 20 shells is more likely to come home with a limit than the guy with the 12 gauge. To me, considering US fighters were normally pretty long ranged and likely to be in the air either as escorts or as CAPs in carrier ops for a long time, that additional firing time offered by 50s might make up for the edge in lethality the 20MM had.
 
While six .50s are lighter than four 20mm guns by the time large amounts of .50 cal ammo are added the .50 cal battery winds up weighing more and offering less.
You are right for the M2 but not the M3 on Sabre. Your quote is
weight of guns and ammo of the F-86 is 353kg. Weight of the Panthers guns and ammo is 363 kg. F-86 wins this one by under 3%.
Firing time was a bit better for the Panther but could be alleviated some by the weight difference.
At ops level you are rarely going to be able to replace the guns in existing aircraft, you can only request that the upcoming planes be fitted with better armament.
I think in this instance, the push for 20s came from above, not from complaints of poor firepower from ops.

This also a bit of a stretch, true the F2H was 3 1/2 years away from ops but what with the end of the war and the wind down the FH-1 was almost 2 1/2 years away from ops. This means the 20mm armed F2H was only about a year (or less) behind the .50cal armed FH-1 in timing.
The FH-1 was slow in development, probably due to the sucking of air out of defense funds after the war. However, had the war continued into '46, as it could have done easily if there was no A-bomb, and the Japanese had fielded rockets/jets such as the Ohka,Kikka, and others, I am sure the Navy would have expedited operations of the FH-1. The F2H would be much slower as it was awaiting the development of the engine.
It also does nothing to show that the Navy was happy with the .50 cal armament since they were examining mockups of aircraft with 20mm cannon in the winter/spring of 1944/45.
Did I say they were happy? They were undoubtedly acceptable or they would not have put them on at all.
Since design work on the FH-1 dates from 1943/44 it may indicate the Navy didn't want to delay the introduction and run up the costs of what they knew was an interim aircraft. With the war winding down the order was cut from 100 to 30 and then bumped back up to 60. Navy may have decided that four M3 .50cal guns equaled the fire power of 6 M2 .50cal guns and so could accept the four .50 armament (with it's lighter weight) for specialized aircraft like the FH-1 the Ryan Fireball and the first F8Fs.
Work on the F2H had started before the first FH-1 Prototype ever flew.
I believe the FH-1 had M2 machine guns. Again, the F2H depended on the development of a new jet engine, certainly a risk, and probably not as able to be accelerated.
No I don't but then I doubt you have loads of comparison data comparing F-86 engagements against the Mig-15 vs. aircraft with 20mm showing that the efficiency of the .50 is so close as to make little difference.
Missing Migs testifies to effectivity.
We have accounts of Pilots getting Mig-s in their sights several times and getting hits each time (same aircraft) before the Mig goes down.
Of course, it takes more hits to down a Mig. It has also has more chances of hits. In the same situation, the slower firing 20s may not have hit at all.
We have accounts of Migs returning home with 40-50 .50 cal hits. they may have been flying junk but they made it.
You know that without the data on Migs that did not make it back with only few 50 cal hits makes this type of data statistically useless.
Here we go with the "if it worked it must be good" argument. we are also into the variables. Different rates of fire, different ammunition, and a few anecdotes.
Your reference does say the M2 was not very efficient compared to the cannon but
performance of the .50 Browning: as has already been stated in this study, "the preferred US armament fit [of six or eight .50 HMGs] was effective for its purpose
. If it was effective, how could double the firepower be marginal?
How do you know the Migs were no more tough than the German fighters? you do have structural analysis of the fighters showing strength of the various aircraft?
I will admit I don't have that information, but the Mig 15 weighed about 460lbs less than a Me 262 did empty, it had a slightly smaller wing and it's single engine weighed about 240lbs less than ONE of the engines on the Me 262. Without engines the Mig 15 is about 1500lbs heavier than a 262 and is a bit smaller. Germany plane "MUST" be just a sturdy due to "German engineering" right?

Actually, you have a bit of an argument here in that the one Mig engine reduced the critical area of hit, and the big centrifugal compressor is probably more rugged. Otherwise, I suspect ruggedness between the Me and Mig is not much different.

The fact that the Mig could fly over 140mph faster has nothing to do with why it might have to be built just a bit stronger.

I don't even know where you came up with this idea. The reason the Mig was 140 mph faster is due to swept wings and 25% more power due to a Nene clone.

The bit about the center line guns needs a bit of thinking too, Center line guns may have a higher hit probability, they don't do a thing for the effectiveness of the hits that are obtained.

Well, this is true


Germans are the ones that figured that centerline guns were worth twice what wing mount guns were but then the Germans were usually mounting a mish-mash of guns with different trajectories and times of flight. A lot of the early German wing mount guns had additional problems.

This itself seems to be a mish-mash. Okay, let's go ahead and do a little thinking. Wing guns must be focused. They can be focused at one range, which means outside that range, bullet strikes lose significant probably. They can be focused in pairs, but then only two guns are in range, and again, other guns lose significant probability. Guns mounted on the centerline are always focused and range is no factor, only ballistics and when ballistics are proper, full impact of the guns are available and probability of each bullet hitting is the same, a big improvement.

you are right, nothing "succeeds like success" and thinking like that kept the smooth bore musket and cannon in use for decades ( if was good enough for Wellington at Waterloo.......) and was the rallying cry for every Colonel Blimp in many armies/countries for 150 years (or longer). It kept the bolt action repeating rifle in use in most countries during WW II (if was good enough in WW I........) by the most armies realized they needed to change it was too late.
While battlefield input is good it has too many variables to give a really accurate picture of weapons performance ( was that tank at 30 degrees or 40 degrees when the projectile hit? 800 yds or 900yds? measured not guessed). It can confirm or contradict range testing but trying to get reproducible results is a bit a difficult.
It is also usually just a bit late for weapons development too. Most aircraft guns took 4-6 years for "new guns" (some longer) to go from drawings to service weapons. Waiting until your current weapon/s aren't working (succeeding) to tool-up, manufacture, issue and combat test new weapons (even if already designed and range tested) can leave you behind the curve.
You are partially correct in that progress and technology must advance, however, as I have said before, there is a saying in engineering that "better is the enemy of good enough". The general philosophy for the US in fighting the war was to build "good enough" weapons en masse and provide the Brits, Canadians, Aussie, Kiwis, Reds, Brazilians, South Africans, etc, etc, etc, and, the American military with hordes of 50 cal aircraft, Sherman tanks, Liberty ships, and so forth and just overcome the enemy with Quantity. It worked fine. The Germans didn't seem to understand that and wasted limited resources on a variety of weapons, many of which only diverted resource from those that were effective.

You are correct, no desperation shown there. Stupidity yes. Or is it the "Nothing succeeds like success" syndrome and believing their own kill/loss ratio claims at the time? Or admitting the Navy was right?

How many Migs were downed by those correct Navy resources? How many Navy aces were there in Korea? Maybe if the Navy had been more interested in joining the AF in the parallel development of the Sabre-based Fury instead of the much poorer performing F9F, they may have had a more fighting role than ground support and interdiction. They may have been correct in armament, but were really lousy in airframe design direction and missed an entire air-to-air war, but, hey, they had good cannons.

Lets follow the logic here, 20mm guns are better for "difficult to target (low probability of hit per projectile?)" that were fleeting in nature, try and get a second firing pass on the same target with a night fighter, and tougher targets yet the 20mm guns were not good for daylight targets that were easier to target and while quicker in motion could usually be followed better both before and after the firing period. And the fighter targets required fewer hits to down.

I got lost in the logic. Remember, higher probability of hits favors the faster firing gun. I think the probability of hits per projectile is lower for night fighting, which favors the slower, more powerful weapon.
 
I have an in-flight original photo of the 4th P51 to come off the assembly line. It has 20mm cannons. Verified by Wright Pat AFB Historical division. I don't have the pic on this computer. I'll try to get it and put it up, if there's interest. i guess they switched to 50's pretty quick.
 
Depending on the fighter in question the difference is not all that great. The F4U is probably the only US fighter that was equipped with both guns while using the same engine/airframe.*
The ones with the .50cal guns carried (when full) 2350rounds of ammo. 400 rounds for each of the inboard and middle guns and 375 rounds for the outboard gun. 400 rounds at 13 rounds per second will last 30.8 seconds.
The ones with the 20mm cannon carried (when full) 924 rounds of ammo. 231 rounds per gun? at 10 rounds per second that is 23 seconds of firing time or just about 74% of the firing time of the .50 cal armed planes or equal to the firing time of a fighter with 300 rpg of .50 cal ammo (any P-40 or most P-47s carrying under wing loads).

The British did an analysis of gun camera footage and found that cannon armed Spitfires fired an 'average' of 17 rounds per gun per burst from their 20mm guns, hit or miss, or 1.7 seconds per burst. The cannon armed Corsair has enough ammo for 13 bursts or firing opportunities. While there are always exceptions and what ifs just how many firing opportunities do you need to provide for?

for the shotgun analogy this like letting the the guy with the 20 gauge keep his 20 shells but letting the guy with 12 gauge have 15 shells ( by the way, while the guns are heavier the 924 20mm shells are about 125lbs lighter than the 2350 .50cal rounds), maybe the 20 gauge comes out on top but the results are going to be a lot closer. Then try hunting bigger birds and using larger shot. 20 shells with one oz of no 4 shot vs 15 shells with 1 1/4- 1 3/8 oz of No 2s?

any single engine WW II aircraft (Il-2s aside?) that took 3-4 20mm hits was pretty much out of the fight even if it doesn't go down. While many aircraft may have succumbed to 9-12 .50 cal hits I don't think there was quite the assurance of ending the fight with that few hits. Think three 20mm hits in one wing vs 8-10 .50 cal hits in one wing.

*The P-51s with the 20mm cannon were Allison powered and had several hundred HP less than the P-51B,C,D. I am not sure how much space was available in the Allison wing for guns and ammo. No Allison powered plane carried more than 4 .50 cals in the wing or 2 .50s and 4 .30s.
 
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You are right for the M2 but not the M3 on Sabre. Your quote is

Firing time was a bit better for the Panther but could be alleviated some by the weight difference.

Gee, I keep getting told how important the longer firing time of the .50 cal is yet the Sabre has a firing time of 13.4 seconds. to equal the firing time of the Panther you need another 216 round of .50 cal ammo or over 60lbs (27kg) which is well in excess of the 10kg weight difference.

Missing Migs testifies to effectivity.

Missing how? not engaging or engaging and then missing? Do you have a details?

You know that without the data on Migs that did not make it back with only few 50 cal hits makes this type of data statistically useless.

Lets flip it around then, a Panther fires 48-50 rounds a second, the F-86 fires 120. Given similar firing solutions/conditions they should make the same percentage of hits. DO you think a Mig could make it back with 15-18 20mm hits?

Actually, you have a bit of an argument here in that the one Mig engine reduced the critical area of hit, and the big centrifugal compressor is probably more rugged. Otherwise, I suspect ruggedness between the Me and Mig is not much different.
I don't even know where you came up with this idea. The reason the Mig was 140 mph faster is due to swept wings and 25% more power due to a Nene clone.

I "came up" with this "idea" because the aerodynamic loads on an aircraft go up with the square of the speed. The forces that try to tear off the wings and other parts. A plane that flies at 640mph has 40% stronger forces acting on it than one at 540mph. If you keep the same safety margin in construction the 640-680mph plane should be built sturdier than a 540mph airplane. I am not saying it needs to be 40% heavier but something in the structure has to be heavier.

It has nothing to do with the engine power or aerodynamics that allow it to reach those speeds, it has a lot to do with surviving those speeds.

This itself seems to be a mish-mash. Okay, let's go ahead and do a little thinking. Wing guns must be focused. They can be focused at one range, which means outside that range, bullet strikes lose significant probably. They can be focused in pairs, but then only two guns are in range, and again, other guns lose significant probability. Guns mounted on the centerline are always focused and range is no factor, only ballistics and when ballistics are proper, full impact of the guns are available and probability of each bullet hitting is the same, a big improvement.

The wing gun thing also depends on the target. Against a small single engine target it is quite possible that the wing guns have markedly lower hit probability. Against a twin engine bomber the difference is nowhere near as great. Even on the big American planes the guns were only 13-15ft apart. On some smaller planes they may be 11 feet apart. With few pilots firing from 50yds away or closer the actual "spread" is even closer. Against the twin engine bomber with a 6-7 foot wide fuselage, large wing roots and the engine nacelles the pilot with wing guns only has to worry about being "off target" if he is firing at ranges beyond the convergence zone. If he is doing that he has a whole bunch of other things affecting his hit probability. Like range and needing the proper lead or deflection. guns on the centerline, in order to be always "focused" need to have the same ballistic properties. The same (or close) muzzle velocity and projectiles with similar drag. Not a problem of the F-86, a big problem for some of the German combinations of hub gun and cowl guns.

You are partially correct in that progress and technology must advance, however, as I have said before, there is a saying in engineering that "better is the enemy of good enough". The general philosophy for the US in fighting the war was to build "good enough" weapons en masse and provide the Brits, Canadians, Aussie, Kiwis, Reds, Brazilians, South Africans, etc, etc, etc, and, the American military with hordes of 50 cal aircraft, Sherman tanks, Liberty ships, and so forth and just overcome the enemy with Quantity. It worked fine. The Germans didn't seem to understand that and wasted limited resources on a variety of weapons, many of which only diverted resource from those that were effective.

Over coming the enemy with quantity is fine, as long as you are one of the generals, not so good if you are an enlisted man.
What is wanted is a happy medium. There was no great technological risk to using the the 20mm Hispano, just swallow their pride, admit they were wrong and shorten the chamber 1/16 of an inch and tighten up some of the tolerances. Instead they spent lord knows how much money on the .60 caliber projects and other high velocity projects which went nowhere. Fortunately the US had the resources to allow a few projects to go down the rat hole without screwing everything up. The US had it's share of projects that never should have had metal cut. The US M6 heavy needed a serious rethink while still on paper as did the T95 tank destroyer. This doesn't mean that the M4 should have been produced as long as it was with the original gun.

I got lost in the logic. Remember, higher probability of hits favors the faster firing gun. I think the probability of hits per projectile is lower for night fighting, which favors the slower, more powerful weapon.

Think about it. For night fighting they used slower firing, lower probability of hit weapons in a situation were firing time (time available to do damage) was limited. Why is this more favorable to the slower, more powerful weapon but using the same weapon in daylight with more firing time (time to do damage) is less limited is NOT supposed to be favorable to the slow firing gun?
 
It is a mistake to believe that the guns on US fighters were all sighted in to converge at a certain point because they were not. Some were, some were sighted in to converge at different points, say 200 yards 250 yards and 300 yards and some were sighted in to give a box type pattern. That shows that some, probably most pilots were not great gunners. Also, in the Navy fighters ( I am not sure about the AAF fighters) the guns were so loose in the mounts, they were impossible to sight in to converge very close together, especially at extreme ranges.

I believe that comparing WW2 fighters with Korean War F86s as far as firing times doesn't make much sense. The Navy fighters could be in the air as long as four or more hours and the AAF fighters, especially the P51 somewhat longer. Firing times for them could be very important. The F86s? Maybe two hours and engaging more than one opponent per mission probably fairly rare. In WW2, on an escort mission or as CAP in carrier ops, it would be important just to have some ammunition to fire when beating off interceptors or intercepting bombers or torpedo planes. If you discouraged the enemy or interfered with his aim, you were being effective. At one point in one of the early Pacific battles during the Guadalcanal Campaign, the Wildcats in the CAP were so low on fuel thay had to make runs only in normal power. Just doing that with some ammo to fire helped keep the carrier from being hit.

According to Dean, the early P51 with 20 mms carried 125 rounds per gun which gave it a firing time of 12.5 seconds. There were quite a few F6Fs equipped with two 20 mms and four 50 BMGs. The 20mms carried 225 rounds per gun for a firing time of 22.5 seconds and the 50s, 400 rounds per gun for a firing time of 26.7 seconds. Sounds like the ideal solution for a big fighter with a big wing?
 
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Gee, I keep getting told how important the longer firing time of the .50 cal is yet the Sabre has a firing time of 13.4 seconds. to equal the firing time of the Panther you need another 216 round of .50 cal ammo or over 60lbs (27kg) which is well in excess of the 10kg weight difference.

We are playing ping pong here but here goes anyway

60 lbs is well in excess? That's less than the weight differences between some pilots. I won't say which weight end I would come in on. That is basically immeasurable in performance impact.



Lets flip it around then, a Panther fires 48-50 rounds a second, the F-86 fires 120. Given similar firing solutions/conditions they should make the same percentage of hits. DO you think a Mig could make it back with 15-18 20mm hits?
Good point. Of course you are willing to verify that the source of the numbers of 50 cal hits are indeed reliable and not the type to try to overestimate in order to emphasis the strength of the Mig, right?

Also, 50 rounds from a sabre is about half a second of fire. This could have easily been fired at a great distance, perhaps at a fleeing enemy, or to distract a Mig on the tail of a friendly aircraft, and strike with such low delta velocity as no major damage could occur. I suspect this was not rare and probably added to the stories of Migs returning with many bullet holes in them but little damage.

This would be a plus for the 20 in that, even at low delta velocity, the round maintains some level of lethality, although probably reduced.

I "came up" with this "idea" because the aerodynamic loads on an aircraft go up with the square of the speed. The forces that try to tear off the wings and other parts. A plane that flies at 640mph has 40% stronger forces acting on it than one at 540mph. If you keep the same safety margin in construction the 640-680mph plane should be built sturdier than a 540mph airplane. I am not saying it needs to be 40% heavier but something in the structure has to be heavier. It has nothing to do with the engine power or aerodynamics that allow it to reach those speeds, it has a lot to do with surviving those speeds.

Aircraft are not stressed to level flight speeds but to speeds expected to be reached in combat. The Me-262 could reach high mach and did so in dive test. One pilot even claimed Mach 1, but that is unreasonable. Like the Me, the Mig was incapable of Mach flight and was probably not stressed to higher speeds than the Me. It did have a higher mach limit, but that was due to aerodynamics, ie, transonic airflow, not structure. The only real reason the Mig was faster than the Me was swept wings and bigger engines, not structure.


The wing gun thing also depends on the target. Against a small single engine target it is quite possible that the wing guns have markedly lower hit probability.

Which is what we are talking about.

Over coming the enemy with quantity is fine, as long as you are one of the generals, not so good if you are an enlisted man.
What is wanted is a happy medium. There was no great technological risk to using the the 20mm Hispano, just swallow their pride, admit they were wrong and shorten the chamber 1/16 of an inch and tighten up some of the tolerances. Instead they spent lord knows how much money on the .60 caliber projects and other high velocity projects which went nowhere. Fortunately the US had the resources to allow a few projects to go down the rat hole without screwing everything up. The US had it's share of projects that never should have had metal cut. The US M6 heavy needed a serious rethink while still on paper as did the T95 tank destroyer. This doesn't mean that the M4 should have been produced as long as it was with the original gun.

The risking of war fighters in order to wage effective wars has been and is a historic accord. The only other comments I have is that there is a big inertia due to schedule and cost impacts to maintain the logistic train status quo and change must meet a high criteria before implementation. Even though the HS 20mm was a superior weapon to the M2, obviously it was not felt that the capability did not improve the weapons systems enough to meet this high criterion. Lack of reliability of the American 20 probably added to the inertia.

It is interesting that the Navy was so excited about the 60 cal that they tried to change their contracts to "put a hole in the plane that a .60-caliber will go in".

Think about it. For night fighting they used slower firing, lower probability of hit weapons in a situation were firing time (time available to do damage) was limited. Why is this more favorable to the slower, more powerful weapon but using the same weapon in daylight with more firing time (time to do damage) is less limited is NOT supposed to be favorable to the slow firing gun?

Statistics do not support this. I did not include some data to keep the post reasonable and not bore people. This is a summation.

As accuracy, i.e. probability of projectile hit, increases, the faster firing gun increases in effectivity at a faster rate than the slower firing gun. The opposite is true also, as accuracy is reduced, the slower firing gun increases effectivity at a faster rate than the faster firing gun.

As firing time increases, the faster firing gun increases in effectivity at a faster rate than the slower firing gun. At a three second burst and 10% accuracy, the Sabre will land over 23 50cal rounds for every 6 round landed F9Fs 20mms or nearly 4 to 1, better than the 3.5 to 1 with a one second burst. The opposite is true also, as firing time is reduced, the slower firing gun increases effectivity at a faster rate than the faster firing gun.

So, all in all, since night fighting has both low probability of strike and low time of engagement, the 20 mm, even thought it has a lower rate of fire, it packs more wallop and would be more effective. Strange but that's the world of probability.

Now there are lies, damn lies, and statistics, and the dynamics of air to air combat are far more complex that what I have represented here. Vulnerability of an aircraft varies over the surface of the aircraft, angle of hits, velocity drop offs, etc.

However, for a probability of hits 10% or greater, and a burst time of 2-3 second, which is probably typical, the sabre is going to land almost four or more rounds per 20 mm round of the Panther. This is objective analysis. The effectiveness of the 50 cal verses the 20 mm is debatable, but at least according to the Navy, in these circumstances, the Sabre is dealing out more firepower than the Panther, at 500 yds. But, of course, this is marginal, so, what does that make the Panther?
 
However, for a probability of hits 10% or greater, and a burst time of 2-3 second, which is probably typical, the sabre is going to land almost four or more rounds per 20 mm round of the Panther. This is objective analysis. The effectiveness of the 50 cal verses the 20 mm is debatable, but at least according to the Navy, in these circumstances, the Sabre is dealing out more firepower than the Panther, at 500 yds. But, of course, this is marginal, so, what does that make the Panther?

Did you read posting 81 or 109? i.e. that the difference is anything but marginal even at the 10% hit probability.

This might be of interest
http://www.quarry.nildram.co.uk/modern_fighter_gun_effectiveness.htm

Note
gun power of F86 552
gun power of Panther 1000 almost double
 
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Did you read posting 81 or 109? i.e. that the difference is anything but marginal even at the 10% hit probability.

Yes, I did.

This might be of interest
http://www.quarry.nildram.co.uk/mode...ectiveness.htm

Note
gun power of F86 552
gun power of Panther 1000 almost double

Gun power is confusing to me. I have never heard of an aircraft being downed by a gun. Perhaps in WWI, some allied pilot threw his empty Lewis gun at a Dr-1 and knocked the pilot out. Projectiles that strike the aircraft are what downs aircraft. I have stated that, at 10% accuracy, and a burst rate of 2-3 seconds, probability says the Sabre will land about four to one more 50 cals rounds compared to the Panther's 20s. That is statistics. The only problem is what is the effect difference of the two rounds. The value Anthony Williams comes to in Table 1 of the referenced site for the "Damage" of the 50 cal is 46, a number I have not analyzed but will accept at face value. The "Damage" value for the 20x110 shell is 201. Using these values the 20 mm is 4.4 times the "Damage" of the 50. While this is slightly better than the Sabre for the situation stated, it is not a lot, certainly not the value implied by the 1000 to 552 you indicate. Also, the Williams value appears to be calculated at muzzle velocity. Since the 20 will decelerate faster than the 50, its "damage" number will also decrease compared to the 50, by some amount relative to the distance to the target.

The Navy in its analysis, which I suspect was done with testing, although the book doesn't say so, determined that one 20 were equal to three 50s. Their analysis references a 500 yard range for kinetic energy. If their analysis is correct, the previous post I submitted is correct.
 
Gun power was the Chemical energy of the projectile x the rof

I recognised that your calculation showed more hits by the 0.5 something I do not disagree with. All I did in posting 81 was multiply the He component of each shell by the number of hits that you calculated. This resulted in a significant advantage to the 20mm, something you haven't actually disagreed with
 

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