# How would you have armed the P38 if you were to use it as it was used historically?



## pinsog (May 21, 2011)

Personally, I think I would have replaced the 20mm and just had 6 .50's. Since it didn't have to intercept bombers, I don't think the 20mm was necessary. I would rather have all weapons with the same trajectory.

Your opinions?


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## tyrodtom (May 21, 2011)

6 .50's sound good. How about 4 20mm's ? Or would it be wasted against the usual lightweight Japanese airframes it went up against ?


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## Lighthunmust (May 21, 2011)

I think 6 .50s in the nose may not have been possible or if possible not provide enough room for adequate ammunition. Having projectiles with the same trajectory is very desirable. However all types of .50cal ammunition do not have the same trajectory, just closer than differing calibers unless the other caliber is specifically matched to it. There is a .50cal spotting cartridge that is matched to the M40 106mm recoiless rifle for example.


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## Shortround6 (May 21, 2011)

The trajectory difference and time of flight difference wasn't enough different to worry about at any practical range. 

Sight in trajectory chart:


_View: https://www.youtube.com/watch?v=-p8h43TRXwk_


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## pinsog (May 21, 2011)

Shortround6
Did that barrel have any fluid in it? Or was that an empty barrel with an explosive 20mm round detonating inside it?


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## Lighthunmust (May 21, 2011)

Shortround6 said:


> The trajectory difference and time of flight difference wasn't enough different to worry about at any practical range.
> 
> Sight in trajectory chart:
> 
> ...




Shortround6 you're awesome! I should have mentioned that trajectories were "close enough for government work" but your chart proves "a picture is worth a thousand words".


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## Shortround6 (May 21, 2011)

pinsog said:


> Shortround6
> Did that barrel have any fluid in it? Or was that an empty barrel with an explosive 20mm round detonating inside it?



All I know is what's what on the video. There may be longer clips out there. Since everything on site had to be flown in or brought in by sled(?) I would guess there wasn't much of value in the drum (fuel/oil).


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## tomo pauk (May 22, 2011)

I'd go for a homogeneous battery: 5-6 x .50 cals, or 3-4 x 20mm.


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## fastmongrel (May 22, 2011)

If we can have any gun from WWII how about 4 x Beresin B20 cannon. Roughly the same size as a Browning .50 so 4 of them should fit no problem.


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## davebender (May 22, 2011)

*P-38 Mission Requirements.
*Lockheed P-38 Lightning - Wikipedia, the free encyclopedia


> high-altitude "interceptor" having "the tactical mission of interception and attack of hostile aircraft at high altitude.


Other then the occasional enemy recon aircraft the interception of hostile aircraft at high altitude means attacking heavy bombers.

Unfortunately the U.S. Army Air Corps did not have a reliable aircraft cannon. Otherwise I would recommend 4 x 20mm cannon mounted in the nose or along the fuselage sides.


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## Shortround6 (May 22, 2011)

davebender said:


> Other then the occasional enemy recon aircraft the interception of hostile aircraft at high altitude means attacking heavy bombers.
> 
> Unfortunately the U.S. Army Air Corps did not have a reliable aircraft cannon. Otherwise I would recommend 4 x 20mm cannon mounted in the nose or along the fuselage sides.



In 1937 just what constituted a heavy bomber? even going by what was on the drawing boards what was a heavy bomber of 1940-41 going to look like? 

The 20mm Hispano gun may have been the 3rd choice for a cannon. Early proposals may have used a 23mm gun or even a 37mm. The 23mm didn't pan out and the 37mm that made it into service used a feed system that wouldn't fit. The Hispano in the P-38 seems to have given less trouble than in other American installations, perhaps because of the rigid (but heavy) mounting cradle used in the P-38. 
Once the Mission changes to long range flights heavy batteries of 20mm guns may not be a good idea. The Hispano had up to 15 seconds of firing time. even using 300rpg of .50cal ammo gives 21 seconds while 500rpg gives about 35 seconds of firing time. 
It also worked out that no opposing countries actually built heavy bombers in any great numbers. If they had we might have seen alternative armaments. They did plan two 20mm and four .50s for the XP-49.


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## davebender (May 23, 2011)

Boeing B-17 Flying Fortress - Wikipedia, the free encyclopedia


> On 8 August 1934, the U.S. Army Air Corps (USAAC) tendered a proposal for a multi-engined bomber to replace the Martin B-10.


The P-38 was an American fighter aircraft. So I've got to assume the U.S. Army Air Corps had enemy aircraft similiar to the B-17 in mind when they wrote specifications for a high altitude interceptor. Even if nobody else had a B-17 size bomber it was only a matter of time before they did.


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## Shortround6 (May 23, 2011)

By Jan 31 1939 the B-17 design had progressed to the delivery of the Y1B-17A, the 14th airframe in the B-17 series and the first to be equipped with turbo chargers. No armor or self sealing fuel tanks and defense was by FIVE hand aimed .30 cal machine guns in single mounts. Engines had 1000hp for take-off and 800hp at 25,000ft. The first real production model is the "B" with more powerful engines, still no armor or self sealing tanks and still with FIVE .30 cal guns. .50s don't show up (FOUR hand aimed single guns) until the "C" model which was ordered in 1939 and not delivered until the summer of 1940. 

In 1937 just which B-17 equivalent should they have been planning to shoot down? 

The B-17E, which started the series that made the B-17s real reputation wasn't ordered until the summer of 1940.


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## renrich (May 23, 2011)

The P38 had about 15 seconds of firing time with the 20mm and around 33 seconds with the .50s. I expect that the 20mm could be turned off so that only the .50s fired. I think the mix of weapons was good because if the 20mm ran out of ammo there was still a lot of lethality left in the .50s. Unless the .50s were sighted to give a box pattern, those four gun's concenrtrated fire was deadly.


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## davebender (May 23, 2011)

How reliable was the P-38s 20mm cannon during historical combat operations?


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## Jabberwocky (May 23, 2011)

On the P-38 in VIII AF service, the AN-M2 had one stoppage about 1 per 505 rounds in 1944, between Jan-1944 and Jul-1944. Reliability improved markedly about Apr/May-1944, as the P-38 transitioned away from the long-range escort mission to fighter bomber and ground strafing missions. 

This overstates the reliability of the weapon in US service though. In 1942 and 1943, the average reliability was about 1 stoppage per 160-180 rounds, improving to about 1 per 200 in early 1944.

In comparison, the .50 had 1 stoppage per 3,900 rounds on the P-38 between Jan-1944 and Jul-1944. In VII AF service in the same period, average reliability was 1 stoppage per 1447 rounds (1 per 951 for P-51B/C, 1 per 1441 for P-51D, 1 per 1800 for P-47D).


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## Jabberwocky (May 23, 2011)

If it was me I'd arm the P-38 with four B-20s. The gun is an upscaled UB, which fired the potent 12.7 x 108 ammunition.

Its slightly smaller and lighter than the M2 Browning (25 kg vs 29 kg), but the round is slower (750-790 m/s vs 850-880 m/sec) and the RoF is a little lower (800 rnds/sec vs 750-850 rnds/sec).

Against this, the round weighs 2.2 times as much and carries 5-6 times the incendiary material or 6.5 times the amount of HE. The actual ammunition (brass, propellant, round et al) is just 60% heavier than a .50 shell. 

Pound-for-pound, a B-20 has about 2.5 times the potential lethality of a M2 Browning.

Take out the 4 Brownings and the Hispano (total weight of guns an ammunition is a staggering 960lbs/436.5 kg). Replace them with 4 B-20s with 260 rpg (20 seconds firing time) and the whole package comes out to 630 lbs/286.5 kg and a lethality increase of about 30%.


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## wwii:)aircraft (May 23, 2011)

6 .50 cals. Americans weren't really known for their 20mm cannons. 6.50cals in the nose would be devastating. The only way I would choose the 20mm cannon over the M2 .50cal is if the cannon was a Germany Mg 151/20 which has a very high rate of fire.


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## Shortround6 (May 23, 2011)

Jabberwocky said:


> On the P-38 in VIII AF service, the AN-M2 had one stoppage about 1 per 505 rounds in 1944, between Jan-1944 and Jul-1944. Reliability improved markedly about Apr/May-1944, as the P-38 transitioned away from the long-range escort mission to fighter bomber and ground strafing missions.
> 
> This overstates the reliability of the weapon in US service though. In 1942 and 1943, the average reliability was about 1 stoppage per 160-180 rounds, improving to about 1 per 200 in early 1944.
> 
> In comparison, the .50 had 1 stoppage per 3,900 rounds on the P-38 between Jan-1944 and Jul-1944. In VII AF service in the same period, average reliability was 1 stoppage per 1447 rounds (1 per 951 for P-51B/C, 1 per 1441 for P-51D, 1 per 1800 for P-47D).


 
Thank you for the numbers, I had read that the reliability in the P-38 was better than in other planes but I didn't know how much. BTW I believe Tony Williams says that the 'total' armament package for the P-38 weighed 1440lbs IIRC. guns, ammo, mounts, ammo boxes/chutes chargers, heaters, etc. 
Aircraft structure has to be able to withstand the recoil loads. Clever mounts can help absorb the recoil or spread out the impulse over time reducing the peak loads but such mounts will add at least a bit more weight.


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## Jabberwocky (May 24, 2011)

wwii:)aircraft said:


> 6 .50 cals. Americans weren't really known for their 20mm cannons. 6.50cals in the nose would be devastating.



American's aren't known for their 20 mm cannon because they mucked up copying the design from the French (and then the British). Took them most of the war to sort it out. Plus, US 20mm ammunition was initially susceptible to misfires if there was a lightly struck cap. 



> The only way I would choose the 20mm cannon over the M2 .50cal is if the cannon was a Germany Mg 151/20 which has a very high rate of fire.


 
MG 151/20 RoF was good, but not great when it comes to WW2 20 mm cannon:

HS.7 / HS.9: 6.5 rps 
Ho-1 / Ho-2: 7 rps
20mm Type 99-1: 8 rps
20mm Type 99-2: 8 rps
MG-FF: 8 rps
Hispano II: 10 rps
HS. 404: 11.5-12.5 rps
*MG 151/20: 12 rps *
Hispano V: 12.5 rps
Berezin B-20: 13 rps
ShVAK: 13 rps
Ho-5: 14 rps


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## Shortround6 (May 24, 2011)

It also used a lighter shell than the Hispano at a lower velocity. It might have needed a bit more effort or machining time to make too.


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## davebender (May 24, 2011)

> In 1942 and 1943, the average reliability was about 1 stoppage per 160-180 rounds


Thank you. That's the data we need.

I suspect 20mm reliability was, if anything, even worse during 1938 when the P-38 was being designed.

I don't like arming a bomber interceptor with .50cal MGs. But I don't see any other choice during 1938. I'd rather have .50cal MGs that work then 20mm cannons which are jammed.


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## Shortround6 (May 24, 2011)

There was no american 20mm Hispano when the P-38 was designed. Most early P-38s, If they had any cannon installed at all, used the 37mm M9 with a 15 round magazine. None of these went over seas. Some of the early planes, if they mounted guns at all, also use two .50s and two .30s. If this seems light the machine guns alone are double the firepower of the in service P-35 and P-36 even without what ever cannon they planed to use. 
The 20mm Hispano doesn't show up until the "E" model in 1941.

Reliability of the early 37mm M9 was far worse.


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## davebender (May 24, 2011)

How many .50cal MGs can be made to fit on a P-38? I would consider the wing (next to the fuselage) in addition to the aircraft nose. 8 or more would be nice for shooting at enemy bombers.


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## Shortround6 (May 24, 2011)

Wing next to fuselage is where the fuel tanks were. When P-38 was initially worked on they were expecting 1000hp per engine. They hoped a 2000hp twin would equal a 15edit>00<edit hp single engined plane and since there was no real 1500hp on offer AT THE TIME they went with the twin.


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## Lighthunmust (May 25, 2011)

If it is possible to increase the rpg to the four .50s by ditching the cannon that would be my choice of armament with U.S. weapons. With the concentration of fire at all ranges, the relative ease for a few hits to down most axis aircraft, and a target rich environment, four .50 ought to be more than sufficient. As I recall many USN Wildcat pilots were unhappy with the change to six .50s with less ammunition when the F4F-4 replaced the F4F-3. They may have had a point. Perhaps when you consider the marksmanship of the average pilot and lack of todays sophisticated fire control systems; being able to a blast a lot of lead in a long burst or more shorter bursts was better than a lot of lead in a short burst. Even just losing the weight of the cannon and shells may have been a better option to keeping it. Isn't Bong famous for saying what a poor marksman he was during his first tour and how he blasted away at a lot of blue sky.


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## pinsog (May 25, 2011)

The P38 faced few, if any opponents that it needed more firepower than 4 concentrated 50's. Would anyone care to figure out how many rounds you could squeeze in if you eliminated the cannon, its mounts and its ammo? If all I was going to face was either German or Japanese single engine fighters, I think 4 Brownings, no cannon and ALOT of ammo would be my preference.


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## Jabberwocky (May 25, 2011)

Lighthunmust said:


> If it is possible to increase the rpg to the four .50s by ditching the cannon that would be my choice of armament with U.S. weapons. With the concentration of fire at all ranges, the relative ease for a few hits to down most axis aircraft, and a target rich environment, four .50 ought to be more than sufficient.



Why bother? The .50s for the P-38 had 500 rpg. At 750-850 rounds per minute, that's 35-40 seconds of firing time. That's 18-20 2 second bursts, more than enough for the BRIEF dogfights of the period. 

I don't know that US statistics, but British experience was that Spitfire Mk IX pilots rarely used more than 110 of the 120 cannon rounds available to them (about 10 seconds firing time). Pilots will always want more, just on the oft chance there is another target, but the reality was that only a few pilots were good enough to get more than a few firing solutions in a combat situation.

The problem is not the length of firing time, but the capacity of the gun itself to fire sustained bursts. There are WW2 recommendations to pilots on the relation between the length of the burst and how long they should wait until firing the next burst.

Otherwise, you get nasty things happening, like rounds cooking off in the chamber as the gun heats up massively and sympathetic detonations of the rest of the rounds in the ammo box. I've got a first hand account somewhere of a P-47 pilot who had been on a ground strafing mission who though he was running into flak after rounds in his .50s started cooking off an putting holes in his wings.

Its not a video game, where you can just hose away until all ammunition is expended.


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## Lighthunmust (May 25, 2011)

Jabberwocky said:


> Why bother? The .50s for the P-38 had 500 rpg. At 750-850 rounds per minute, that's 35-40 seconds of firing time. That's 18-20 2 second bursts, more than enough for the BRIEF dogfights of the period.
> 
> I don't know that US statistics, but British experience was that Spitfire Mk IX pilots rarely used more than 110 of the 120 cannon rounds available to them (about 10 seconds firing time). Pilots will always want more, just on the oft chance there is another target, but the reality was that only a few pilots were good enough to get more than a few firing solutions in a combat situation.
> 
> ...


 
I actually have quite a bit of experience with firing automatic weapons (on the ground) both in the Army and here in Arizona where civilians can own them. You are very right about restrictions on burst times and frequency. Movies, TV, and video games have certainly distorted the perceptions of most people. All the times you return to base with ammunition will not provide much comfort the one time you run out at the wrong time. With in reason more ammo is always preferable. In the Army we knew we could live for weeks with out food and days without water, but maybe not a second longer without ammo. As I recall Bong also ran out of ammunition on more than one occasion. Perhaps ditching the cannon for the weight savings and servicing requirements would be good enough, but I would prefer if practicable to carry a little extra .50 cal. for the most unexpected and critical moments that so often happen in combat.


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## Shortround6 (May 25, 2011)

to modify the "Thach quote" ----"if you can't hit them in 30 seconds you aren't going to hit them in 40 seconds." 

Every ONE second of firing time for four .50 cal guns weighs about 17 lbs. Granted you are ditching the 20mm but that constituted over 40% of your striking power for as long as the ammo lasted or the gun kept working. 

How long are you going to be flying around at what power settings in order to fire off more than 35 seconds worth of ammo? A P-38L burns just over 5.5 gals a minute at Military power and 6 gallons a minute at WER.


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## pinsog (May 25, 2011)

Jabberwocky, Shortround6

Seriously? Too much ammo? Isn't that like a fighter thats too fast? Too manueverable? A woman thats too hot? 

What about strafing? How many stories have you read where they beat up the target until they ran out of ammo? I would like to hear of anyone who ever heard a fighter pilot say "I sure wish my guns didn't shoot so long before they quit".

David McCampbell shot down 9 Japanese divebombers on one mission and ran out of ammo. Hellcats carried 400 rounds per gun, I believe, how many more could he have gotten if he had another 200 or 300 rounds?(and full fuel tanks, he took off with his tanks half full and ran out when he landed on the carrier)


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## Lighthunmust (May 25, 2011)

Shortround6 said:


> to modify the "Thach quote" ----"if you can't hit them in 30 seconds you aren't going to hit them in 40 seconds."
> 
> Every ONE second of firing time for four .50 cal guns weighs about 17 lbs. Granted you are ditching the 20mm but that constituted over 40% of your striking power for as long as the ammo lasted or the gun kept working.
> 
> How long are you going to be flying around at what power settings in order to fire off more than 35 seconds worth of ammo? A P-38L burns just over 5.5 gals a minute at Military power and 6 gallons a minute at WER.


 
I don't think that does Thatch justice. How about Butch O'hare? He might of run out of ammunition with a six .50 F4F-4 before getting all those bombers headed toward the Lexington. No combatant can ever know for certain how many opponents may unexpectedly show up. As I recall it was only because of the British that the F4F was "upgraded" to six guns. As long as weight of fire is sufficient, without sophisticated fire control equipment it may be better to have more of the sufficient than less of the overwhelming. Insufficient excellence is the enemy of enough good enough.

How long will you be flying? Until you land, alive or dead. I don't think running out of fuel in a dogfight happened to often, especially in a P-38.


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## davebender (May 25, 2011)

You've got me confused. Are we talking about the original 1937 design for the P-38? Or are we talking about the the P-38L which entered service during June 1944? 

The P-38L is 7 years newer then the original specifications. Rather like comparing an Me-109F4 to the original Me-109 prototype powered by a RR Kestrel engine.


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## pinsog (May 25, 2011)

Davebender,

Pick a year. Doesn't matter. Obviously if you were intercepting a "German B17", if they had ever built one, you would arm it differently than if you were killing Zero's. I'm looking at the historical aircraft it actually battled, and I think if I were a pilot of the time I would ditch the cannon and add another couple hundred rounds per gun for the 4 Brownings. It would give you a VERY long firing time. Zero's, 109's and 190's just weren't that tough and I think those 4 Browning packed in the nose would have been devastating to any of those 3 single engine fighters.


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## Lighthunmust (May 25, 2011)

pinsog said:


> Davebender,
> 
> Pick a year. Doesn't matter. Obviously if you were intercepting a "German B17", if they had ever built one, you would arm it differently than if you were killing Zero's. I'm looking at the historical aircraft it actually battled, and I think if I were a pilot of the time I would ditch the cannon and add another couple hundred rounds per gun for the 4 Brownings. It would give you a VERY long firing time. Zero's, 109's and 190's just weren't that tough and I think those 4 Browning packed in the nose would have been devastating to any of those 3 single engine fighters.


 
Even for bomber destruction the never dispersing bursts of four nose mounted .50s is pretty devastating. This would be especially so in the head-on attacks such as those practiced by the Luftwaffe against our B-17s. But of course reliable cannon would be more effective against bombers under most circumstances. One thing to consider though is you would have more .50 ammo to fight your way through the escorts to the bombers.


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## Jabberwocky (May 26, 2011)

pinsog said:


> Jabberwocky, Shortround6
> 
> Seriously? Too much ammo? Isn't that like a fighter thats too fast? Too manueverable? A woman thats too hot?
> 
> ...


 
EVERYTHING on a fighter is a compromise. 

More ammunition = more weight = less maneuverability, lower rate of climb, slower acceleration, lower ceiling, higher fuel consumption ect, ect.

Would you rather have more ammunition to fire, or be better able to get into position to fire?

500 rounds per gun for a HMG is a load-out that few fighters of the period matched.


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## Shortround6 (May 26, 2011)

davebender said:


> You've got me confused. Are we talking about the original 1937 design for the P-38? Or are we talking about the the P-38L which entered service during June 1944?
> 
> The P-38L is 7 years newer then the original specifications. Rather like comparing an Me-109F4 to the original Me-109 prototype powered by a RR Kestrel engine.



I used it because those were the figures I had. 

I believe you missed the point. There are TWO factors that cover combat duration. One is the ammo capacity (firing time) the other is fuel capacity, how much time can you spend at combat and military power and still get home. Since you brought up the 109 look at the "E" in the Battle of Britain, it carried (if they were full) 1000rounds in the ammo containers for each 7.9mm cowl MG. Nearly a full minute of firing time. How many pilots ever used up the total amount compared to the number that broke off combat due to low fuel? Would the Germans have been better served to trade 1000 rounds of 7.9 ammo (leaving 500 per gun) for another 30-35 liters of fuel?


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## davebender (May 26, 2011)

> Would the Germans have been better served to trade 1000 rounds of 7.9 ammo (leaving 500 per gun) for another 30-35 liters of fuel?


I've never heard of mounting fuel tanks in the engine cowl. So I don't think this trade off would be possible on the Me-109.


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## Shortround6 (May 26, 2011)

It probably isn't possible but again, I am trying to point out that combat duration and a fighter's "effectiveness" are dependent on several things. Just having lots of ammo and long firing time (past a certain point) doesn't do much good if the plane is out of fuel. 
If the Germans could have gotten the engine mounted gun to work perhaps putting a 3rd MG 17 through the prop with 500rounds would have been a better bet. 20mm guns run dry in 7-8 seconds, having 50 more seconds of firing time for a pair of 7.9mm guns gets how many victories? having 22 seconds more time after the 20's quit for 3 guns might have been better.


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## pinsog (May 26, 2011)

Jabberwocky,
I agree everything is a compromise, that is why I said "delete the cannon, cannon mount and cannon ammo and replace it with more 50 ammo". The tradeoff is less weight per second for more seconds of firing. IMHO that is a good tradeoff considering the main opponents for this aircraft were rather lighly built single engine fighterslike the Zero and 109 (the 190 being a bit more durable).

Shortround6,
I understand your point, about a fighter carrying somuch ammo that it runs out of fuel before it can shoot it up, but I think it has little merit for one of the longest range fighters of WW2. It is a very vaild argument for ME109, FW190, Spitfires, Hurricanes, etc, but those fighters were fuel critical before they got to the end of the runway. Again I point out David McCambell who left the Essex with 1/2 tank of fuel, shot down 9 Japanese planes, and still ran out of ammo while carrying 400 rounds per gun. If he had left the Essex with a full tank of fuel, he could have used alotmore ammo.


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## davebender (May 26, 2011)

> David McCambell who left the Essex with 1/2 tank of fuel, shot down 9 Japanese planes


I believe some Me-109 pilots achieved more then 9 kills on a single day. Multiple sorties were required but David McCambell also had the option to land for more fuel and ammo.


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## Lighthunmust (May 26, 2011)

I think both sides of the argument being made have very valid points. With the P-38 one thing to consider regarding the weight of extra .50 cal ammunition, which may or may not weigh more than the cannon and shell it would replace, is that it would be in the best possible place to not adversely effect maneuvering. Discarding the less reliable cannon would certainly simplify maintenance and the logistical requirements of supplying two types of ammunition and replacement parts. For the P-38 this may be the best choice because fuel in not much of an issue. Does anyone have reports of P-38s going on missions without functioning or armed cannons due to maintenance or logistics problems? I would not be surprised to learn this may have occasionally happened in the PTO.


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## pinsog (May 26, 2011)

davebender said:


> I believe some Me-109 pilots achieved more then 9 kills on a single day. Multiple sorties were required but David McCambell also had the option to land for more fuel and ammo.


 
Multiple sorties per day is not an option when you fly from England to Germany. When David McCampbell shot down 9 Japanese planes in 1 mission, he broke off contact with targets still available, he shot down no more aircraft that day. If he had more ammo, and a full tank of fuel when he left the ship, how many might he have gotten? Lets put McCampbell in a P38 flying from a nearby island helping defend the fleet, with a full tank of fuel. The P38 already carries 500 rounds per gun, 100 more per gun than the Hellcat. The guns are concentrated in the nose. Could he have knocked down more Japanese dive bombers? Lets make the total 600 rounds per gun, or 700 rounds per gun. What ever the weight of the cannon, its mount and ammo, I would have deleted that stuff and put that much more 50 ammo. That is how I would have armed the P38. IMHO against the aircraft it fought, losing the 20mm would have not been an issue.

Can anyone tell us how much the cannon, its mount, and the 20mm ammo weighed in a P38? That would let us know how much more 50 ammo we could carry with no performance penalty.


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## Lighthunmust (May 26, 2011)

pinsog said:


> Multiple sorties per day is not an option when you fly from England to Germany. When David McCampbell shot down 9 Japanese planes in 1 mission, he broke off contact with targets still available, he shot down no more aircraft that day. If he had more ammo, and a full tank of fuel when he left the ship, how many might he have gotten? Lets put McCampbell in a P38 flying from a nearby island helping defend the fleet, with a full tank of fuel. The P38 already carries 500 rounds per gun, 100 more per gun than the Hellcat. The guns are concentrated in the nose. Could he have knocked down more Japanese dive bombers? Lets make the total 600 rounds per gun, or 700 rounds per gun. What ever the weight of the cannon, its mount and ammo, I would have deleted that stuff and put that much more 50 ammo. That is how I would have armed the P38. IMHO against the aircraft it fought, losing the 20mm would have not been an issue.
> 
> Can anyone tell us how much the cannon, its mount, and the 20mm ammo weighed in a P38? That would let us know how much more 50 ammo we could carry with no performance penalty.




From AHT by Dean page 145, tables 19 and 20.

For the P-38J 
(1) 20mm cannon installed 196 lbs.
20mm ammunition 92 lbs. for all load plans

(4) Cal. .50 Installed 425 lbs.
.50 cal ammunition = normal load 249 lbs. or three alternate loads plans each having 622 lbs.

150 rounds of 20mm ammo weighs 92 lbs.
800 rounds of .50 ammo weighs 249 lbs., 2000 rounds weighs 622 lbs.


I have no idea how much extra rpg could be made to fit with removal of the cannon, but if space would not be a problem, easily 200 extra rpg. Please do the math if you want a precise number.


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## tomo pauk (May 26, 2011)

By the US 100K book, the cannon installation weights 196lbs, with further 92lbs for 150 pcs of ammo (totaling 288; firing time 15sec), while one gun its ammo weighted 261lbs (500 pcs, firing time 33sec). Replacing a cannon with one HMG ammo yields reduction of firepower by 25% (my estimate) for 1st 15 seconds of firing, but increases it by 25% for 2nd 18 seconds. Perhaps 5 x .50cals, tightly grouped, are at least as good as wing mounted 6 x .50cals?


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## Lighthunmust (May 26, 2011)

tomo pauk said:


> By the US 100K book, the cannon installation weights 196lbs, with further 92lbs for 150 pcs of ammo (totaling 288; firing time 15sec), while one gun its ammo weighted 261lbs (500 pcs, firing time 33sec). Replacing a cannon with one HMG ammo yields reduction of firepower by 25% (my estimate) for 1st 15 seconds of firing, but increases it by 25% for 2nd 18 seconds. Perhaps 5 x .50cals, tightly grouped, are at least as good as wing mounted 6 x .50cals?



I think 5 in the nose would be more effective than 6 in the wings regardless of rps because of concentration at all ranges, perhaps 4 would also be. This however requires being a good shot. How many times did the dispersion of 6 in the wing fired outside the point of convergence manage to catch an opponent with just enough to do the job. I personally have seen what one .50 bullet can do to a target and it was impressive.


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## tomo pauk (May 26, 2011)

Perhaps 90% of fighter planes deployed in Eastern front have had hull weapons only, yet I've didn't read that those planes were in disadvantage re. hit probability. Another thing that can be considered is that Fw-190D-9 did have wing guns deleted (ditto for P-39 in VVS service), yet I have to read about complain considering reduced hit probability.



> I think 5 in the nose would be more effective than 6 in the nose



6 in the wings


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## Lighthunmust (May 26, 2011)

tomo pauk said:


> Perhaps 90% of fighter planes deployed in Eastern front have had hull weapons only, yet I've didn't read that those planes were in disadvantage re. hit probability. Another thing that can be considered is that Fw-190D-9 did have wing guns deleted (ditto for P-39 in VVS service), yet I have to read about complain considering reduced hit probability.
> 
> 
> 6 in the wings




Perhaps it would take someone with a fair amount of experience in both to make an accurate assessment. When I think of target sleeve shooting, I'm guessing making hits with 6 in the wing was easier. However, wouldn't the short distance from the cockpit to the nose make deflection shooting easier in a P-38? - Lighthunmust

Whoops! Senior moment. Fixed it. - Lighthunmust


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## fastmongrel (May 26, 2011)

Lighthunmust said:


> As I recall it was only because of the British that the F4F was "upgraded" to six guns.



I have have heard this repeated many time but never understood it. How can the Royal Navy FAA be blamed for lumbering the F4F-4 with 6 guns. The customer for Grumman was the US government and the RN got what it was given under lend lease. Why would Grumman upset the people who were paying its bills to build an aircraft for a customer who had less than zero say in the design and production. I can imagine the RN asking for 6 guns but why would the US government who controlled the contracts listen to them they never did on any other lend lease weapon. If the British wanted something different they had to pay for it and or do the work themselves. A good example is the fuel stowage on escort carriers which wasnt up to RN standards as built, the RN had to have them modified after delivery from the shipyard.


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## Lighthunmust (May 26, 2011)

fastmongrel said:


> I have have heard this repeated many time but never understood it. How can the Royal Navy FAA be blamed for lumbering the F4F-4 with 6 guns. The customer for Grumman was the US government and the RN got what it was given under lend lease. Why would Grumman upset the people who were paying its bills to build an aircraft for a customer who had less than zero say in the design and production. I can imagine the RN asking for 6 guns but why would the US government who controlled the contracts listen to them they never did on any other lend lease weapon. If the British wanted something different they had to pay for it and or do the work themselves. A good example is the fuel stowage on escort carriers which wasnt up to RN standards as built, the RN had to have them modified after delivery from the shipyard.


 
Perhaps because the American decision makers where echelons above reality in comparison to the complaining pilots who were not given a chance to provide imput. Grumman may have seen the handwriting on the wall regarding future fighter armament, or just didn't care one way or the other because nobody in the USN leadership objected. I don't know. I'll check my books.


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## Lighthunmust (May 26, 2011)

fastmongrel said:


> I have have heard this repeated many time but never understood it. How can the Royal Navy FAA be blamed for lumbering the F4F-4 with 6 guns. The customer for Grumman was the US government and the RN got what it was given under lend lease. Why would Grumman upset the people who were paying its bills to build an aircraft for a customer who had less than zero say in the design and production. I can imagine the RN asking for 6 guns but why would the US government who controlled the contracts listen to them they never did on any other lend lease weapon. If the British wanted something different they had to pay for it and or do the work themselves. A good example is the fuel stowage on escort carriers which wasnt up to RN standards as built, the RN had to have them modified after delivery from the shipyard.


 
I have found a secondary sources without specific documentation of this information, just a list of sources. I checked Tillman's "Wildcat" and all I found was that at one time there were two separate production lines at Grumman for F4Fs and Martlets. According to Dean in AHT page 494 Gun Platform and Weapon Performance there were many complaints from USN aviators such as "The reduction of rounds per gun cut the firing time by at least five seconds. That doesn't seem like much, but can be a lifetime in combat". Dean writes "The FM-1 and the FM-2 versions by Eastern went back to four guns with more ammunition per gun. THE BRITISH, WHO INSTIGATED THE SIX GUN ARRANGEMENT THE -4 VERSION USED FOR COMMONALITY OF MANUFACTURE, STAYED WITH THIS CONFIGURATION." (capitalization added for emphasis) Dean is a respected source. I think Grumman, who would soon stop making Wildcats to concentrate on Hellcats, decided to make a production decision to reduce the costs of running two production lines and the USN Brass did not care.


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## Lighthunmust (May 27, 2011)

Do we ditch the cannon for more .50cal ammo and/or an extra M2 or two?


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## Shortround6 (May 27, 2011)

Lighthunmust said:


> Do we ditch the cannon for more .50cal ammo and/or an extra M2 or two?



Ditching the cannon for more ammo seems rather pointless. You are trading 40% of your striking power in the first 15 seconds for extended firing time for the American fighter that carried more rounds per gun for it's .50s than any other. If the P-38 is carrying 500rpg it has another 5 seconds of firing time over a P-47 carrying 425 rpg and 7 seconds more firing time than the Navy fighters. It has 2 1/2 times the firing time of some P-40s. 

Swapping the 20mm and it's 150 rounds of ammo for a 5th M2 with 500rounds saves about 64lbs. you are giving up about 28% of your firepower in the first 15 seconds for 25% more firepower in seconds 16-33 compared to a normal P-38. 

This makes more sense than the first option. 

Trying to add a 6th M2 is self defeating. If you keep all six guns at 500rpg you will have increased the armament weight by about 286lbs. If you have room for the ammo. 1000 rounds of .50 cal ammo takes up how much volume compared to 150 rounds of 20mm? 
Less ammo for all six guns or 4 guns keep 500rpg and two guns run out a lot sooner? 
That 286lb is over 900 rounds of .50 cal ammo. How do you want to divvy it up?


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## pinsog (May 27, 2011)

I seriously dont think you need a 20mm cannon to shoot down a Zero or a 109 or for that matter even a 190. 4 Bronwing 50,s that close together will annialate anything short of anAmerican medium bomber. Using a 20mm on any of those 3 planes is like using buckshot on a dove


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## Shortround6 (May 27, 2011)

pinsog said:


> I seriously dont think you need a 20mm cannon to shoot down a Zero or a 109 or for that matter even a 190. 4 Bronwing 50,s that close together will annialate anything short of anAmerican medium bomber. Using a 20mm on any of those 3 planes is like using buckshot on a dove



Dove's don't shoot back


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## pinsog (May 27, 2011)

I dont really think you need a 20mm cannon to shoot down a Zero, ME109 or even a FW190. Using a 20mm on anyone of them is like using buckshot on a dove


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## Shortround6 (May 27, 2011)

pinsog said:


> I dont really think you need a 20mm cannon to shoot down a Zero, ME109 or even a FW190. Using a 20mm on anyone of them is like using buckshot on a dove


 
I believe you have said that already.

Now, could you have GUARANTEED in 1942 or 1943 that those 3 aircraft are the ONLY aircraft the P-38 would have to shoot down? 
No Me 110s, no Me 210/410s, no Ju-88s, No Do 217s. No Japanese Sally's, or Betty's. How about an Emily or two?

And if I had to do a head on pass at at a Fw 190 that had four 20mm cannon I would want all the firepower I could get in my plane.


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## pinsog (May 27, 2011)

I didnt realize I double posted. So much for multi tasking. If I were in a single engine fighter I would want 6 50's or something. The sole reason I think the Lightning could get away with 4 is because they are all concentrated. I guess to each his own. We'll just have to disagree. I'd want more firing time and you'd want more hitting power. I think we can all agree it's a good thing the Germans didn't have it. The P38-K with German cannon would have been a devistating bomber destroyer. So would a cannon armed P47.


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## Lighthunmust (May 27, 2011)

Shortround6 said:


> Ditching the cannon for more ammo seems rather pointless. You are trading 40% of your striking power in the first 15 seconds for extended firing time for the American fighter that carried more rounds per gun for it's .50s than any other. If the P-38 is carrying 500rpg it has another 5 seconds of firing time over a P-47 carrying 425 rpg and 7 seconds more firing time than the Navy fighters. It has 2 1/2 times the firing time of some P-40s.
> 
> Swapping the 20mm and it's 150 rounds of ammo for a 5th M2 with 500rounds saves about 64lbs. you are giving up about 28% of your firepower in the first 15 seconds for 25% more firepower in seconds 16-33 compared to a normal P-38.
> 
> ...


 
What you write makes perfect sense. It also may not make perfect sense it you consider the logistical support necessary for the 20mm, known reliability issues, lower rate of fire, frequent target rich environment of easy to disable opponents at the beginning of P-38 service, and poor marksmanship of almost all pilots. Fighter pilots miss more often than hit, as Bong's experience demonstrates.

This question cannot be definitively answered with the data so far presented in this thread. The trend of the majority opinion appears to be ditch the cannon. My experience is that Majorities are frequently disastrously wrong. I am going back to Bodie's book to look for better data.


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## pinsog (May 28, 2011)

Shortround6 said:


> I believe you have said that already.
> 
> Now, could you have GUARANTEED in 1942 or 1943 that those 3 aircraft are the ONLY aircraft the P-38 would have to shoot down?
> No Me 110s, no Me 210/410s, no Ju-88s, No Do 217s. No Japanese Sally's, or Betty's. How about an Emily or two
> ...


 
FM2 Wildcats handled Sally's, Betty's, and Emily's just fine, and it's 4 50's weren't concentrated like a P38.

Early P51's handled all those German aircraft also, and again, it's 4 50's weren't concentrated like a P38.

I would also avoid head on passes on any bomber destroyers no matter what my plane was armed with if at all possible, but with 4 flatter shooting 50's concentrated in the nose, you should be getting hits on him before he gets hits on you, and with no dispersal of your rounds like on a single engine fighter.

We just think different. I'd rather have more firing time and you'd rather have more hitting power. Just like deer hunting, I've seen everything in deer camp from .223 up through .375 and everyone swore their gun was the best deer rifle.


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## NZTyphoon (May 28, 2011)

pinsog said:


> I dont really think you need a 20mm cannon to shoot down a Zero, ME109 or even a FW190. Using a 20mm on anyone of them is like using buckshot on a dove


 
In air-to-air combat the idea is to shoot down an aircraft in as little a time as possible, because the more time a fighter pilot had to concentrate on one target meant there was more time for an opponent to get in some shooting of their own. Most combat during WW2 involved a few seconds of firing time, if that - ideally a diving pass from behind - there simply wasn't the time to line up and squeeze off a precision shot as in deer hunting. If a 20mm cannon could do the job more quickly and efficiently than .50s alone it didn't matter if there was some "overkill". As someone famous once quipped (and I wish I could remember who) "You don't need a sledgehammer to crack a nut, but if you want to destroy the nut use the sledgehammer."

Yep, FM2s and Mustangs could handle the job, but then the P-47 with 8 .50s and P-61s with four .50s and four 20mm cannon shot down aircraft most efficiently, as well as being highly effective at ground attack.


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## Lighthunmust (May 28, 2011)

NZTyphoon said:


> In air-to-air combat the idea is to shoot down an aircraft in as little a time as possible, because the more time a fighter pilot had to concentrate on one target meant there was more time for an opponent to get in some shooting of their own. Most combat during WW2 involved a few seconds of firing time, if that - ideally a diving pass from behind - there simply wasn't the time to line up and squeeze off a precision shot as in deer hunting. If a 20mm cannon could do the job more quickly and efficiently than .50s alone it didn't matter if there was some "overkill". As someone famous once quipped (and I wish I could remember who) "You don't need a sledgehammer to crack a nut, but if you want to destroy the nut use the sledgehammer."
> 
> Yep, FM2s and Mustangs could handle the job, but then the P-47 with 8 .50s and P-61s with four .50s and four 20mm cannon shot down aircraft most efficiently, as well as being highly effective at ground attack.


 
All you write is true. However, the options with the P-38 prevent the use of four 20mm cannon and probably more than five .50s. I also think many agree the concentration of fire in the nose in most cases make an accurate 2-3 second burst of five .50s as effective in reality as the 4 MG +1 AC. You only need to sufficiently crack the nut, the ground will destroy the nut, and your logistics will be easier. Fighter pilots miss more often than hit. Fighter pilots are more often targets than shooters. "Good generals study tactics, great generals study logistics".


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## Shortround6 (May 28, 2011)

pinsog said:


> Early P51's handled all those German aircraft also, and again, it's 4 50's weren't concentrated like a P38.



then why did they go to six guns? ground strafing? 


pinsog said:


> I would also avoid head on passes on any bomber destroyers no matter what my plane was armed with if at all possible, but with 4 flatter shooting 50's concentrated in the nose, you should be getting hits on him before he gets hits on you, and with no dispersal of your rounds like on a single engine fighter.



You don't always have a choice, This flatter shooting advantage of the .50 may be a lot of hoopla with little to back it up. Yes the .50 shoots flatter as can be proved by any number of trajectory tables. But at any practical air to air range in WW II the difference of even a couple of feet of trajectory doesn't make a lot of difference. Very few pilots were trying 1000yd shots and against all but the smallest fighters the target is 5-6 feet high or larger. Your .50 gets him right smack dab in the middle and his not so flat shooting 20mm blows the bottom out of your fuselage, what was the practical difference again? 
Shorter time of flight is more of an advantage. 
In a head on pass with 400mph aircraft your are closing on each other and around 400yds per second. Time on target is going to be very brief, and it doesn't matter if you puncture every fuel tank he has, wreck his oil cooler, hole a hydraulic line and the oil tank and even knock a cylinder of his radial, he is a goner for sure, but none of the damage will take effect before his shells hit you. A single 20mm won't blow him out of the sky but the more damage you can do in a shorter amount of the time the more successful you will be.



pinsog said:


> Just like deer hunting, I've seen everything in deer camp from .223 up through .375 and everyone swore their gun was the best deer rifle.



Just like the doves, the deer aren't shooting back. 

Somebody once said about African hunting ( close to this) "when you are standing 50yds away from an angry elephant, anything you can hold in your hands seems too small"

If four .50s worked so well Against the Japanese planes why was the Navy trying to mount a pair of 20mm guns in the F6F for two 20mm and four .50s and why were they trying to mount four 20mm in the Corsair? Not to mention shifting to the 20mm guns for practically every fighter except the very first F8Fs and FH Phantoms? They didn't believe their own combat results?


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## Shortround6 (May 28, 2011)

Lighthunmust said:


> All you write is true. However, the options with the P-38 prevent the use of four 20mm cannon and probably more than five .50s. I also think many agree the concentration of fire in the nose in most cases make an accurate 2-3 second burst of five .50s as effective in reality as the 4 MG +1 AC. You only need to sufficiently crack the nut, the ground will destroy the nut, and your logistics will be easier. Fighter pilots miss more often than hit. Fighter pilots are more often targets than shooters. "Good generals study tactics, great generals study logistics".



Once again, the "nut" isn't shooting back. How long can a liquid cooled engine last with a holed radiator? Or any engine last with a holed oil tank or shot away oil line. The plane may not make it's home field and the ground will destroy the "nut" but will the nut get in a burst or two at a wingman or squadron mate? 
How many enemy planes were claimed as "damaged" compared to how many shot down?
What percentage of P-38 pilots, with out having gone strafing, landed with empty guns? What percentage even used all the cannon ammo, assuming the gun didn't jam? 
Knowing the ACTUAL need for more ammo rather than a PERCEIVED need for more ammo would go a long way in answering this question.


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## pinsog (May 28, 2011)

Shortround6,

"If four .50s worked so well Against the Japanese planes why was the Navy trying to mount a pair of 20mm guns in the F6F for two 20mm and four .50s and why were they trying to mount four 20mm in the Corsair? Not to mention shifting to the 20mm guns for practically every fighter except the very first F8Fs and FH Phantoms? They didn't believe their own combat results?"

None of these aircraft had guns concentrated on the centerline like the P38 either. Was it Gunther Rall that said something like 2 guns on the centerline was worth 4 in the wings? Someone help me with that quote please. 

I'm definately not saying your wrong, I could actually argue your side of the argument and I'm sure you could argue mine to, the only reason I'm saying we could ditch the cannon is how fragile the opponents it was facing was, Zero's and ME109's were particularly fragile. If I was in a P38 having to fight P47's, I'd keep the cannon! But, also I have been reading war stories for just over 30 years now ALOT of times the pilots were quoted as saying they were out of ammo and ran for home.

You said doves, deer and nuts don't shoot back, neither do Zero's, 109's and 190's.....................as long as your behind them.;o)


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## Lighthunmust (May 28, 2011)

Shortround6 said:


> Once again, the "nut" isn't shooting back. How long can a liquid cooled engine last with a holed radiator? Or any engine last with a holed oil tank or shot away oil line. The plane may not make it's home field and the ground will destroy the "nut" but will the nut get in a burst or two at a wingman or squadron mate?
> How many enemy planes were claimed as "damaged" compared to how many shot down?
> What percentage of P-38 pilots, with out having gone strafing, landed with empty guns? What percentage even used all the cannon ammo, assuming the gun didn't jam?
> *Knowing the ACTUAL need for more ammo rather than a PERCEIVED need for more ammo would go a long way in answering this question.*


 
That is certainly a great question. I wonder how hard it will be to find the data to answer it. If a "nut" isn't cracked enough to prevent it from shooting back, it ain't cracked. Four .50s cracked alota of "nuts". If you are making solid hits with five nose mounted .50s the end result will not be much different from 4+1, maybe not a messy in the air but just as messy when everything hits the ground. I am surprised the subject of Howard and the situation resulting in his Medal of Honor hasn't been mentioned. Four was enough until he ran out of ammunition but not guile and courage. We already have ample examples of USN aviators thinking four was enough until they ran out of ammunition.


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## Njaco (May 28, 2011)

How many .50 bullets did it take to bring down...say, a 109?
How many 20mm shells?

Whats the weight of 4 fully loaded .50s and 2 fully loaded 20mm?

I would think that if it takes one or two shots from a 20mm to take out an opponent that leaves more ammo to get more compared to the .50s.


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## pinsog (May 29, 2011)

Njaco said:


> How many .50 bullets did it take to bring down...say, a 109?
> How many 20mm shells?
> 
> Whats the weight of 4 fully loaded .50s and 2 fully loaded 20mm?
> ...


 
It is a legitimate point IF you could connect with every round. But if you could connect with every round I would put the 37mm out of the P39 in it with 100 rounds and shoot down everything in the air. You have alot more ammo to miss with carrying 50's than you do when carrying 20mm. Again,like shooting doves with buckshot, sure buckshot will kill a dove, but you gotta hit it first. It takes more #8 birdshot, but you alot more likely to hit it to.


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## Lighthunmust (May 29, 2011)

I stopped being lazy. I broke out Dean and Bodie.

From Dean’s “America’s Hundred-Thousand” pages 133, 134, 135 - 

Cyclic rate of the 20mm is 600 rpm
Cyclic rate of the .50 BMG is 800-900 rpm

Even if the cyclic rates given are a little high, the cannon is almost certainly 30% slower than the .50 BMG. This means that there is more of a gap in all directions of flight between fired cannon ammunition and consequencly a greater chance for a miss. - Lighthunmust 

Firing time of the P-38s 20mm is 15secs
Firing time of the P-38s .50s it is 33.3 seconds.

This means that only the four .50s were available for more than half the firing. Considering how many times I have read of pilots missing with their first bursts, the .50s were probably accounting for most of the killing. - Lighthunmust

Total projectile throw weight per second for P-38 with 4+1 = 9.26 lbs
Total projectile throw weight per second for P-40E with 6x.50=9.54 lbs

Granted that cannon shells explode at all ranges. The shortness of engagement ranges somewhat negates this advantage especially when considering the limited number of hits possible per second. More rounds per minute and for more bursts would be available for aircraft known to be easy (includes most WW2 aircraft) to destroy - Lighthunmust 

From Bodie’s “The P-38 Lightning” -

The following is a summary of two paragraphs from p.82 and a caption from p.87:

In March 1942 three different P-38 nose configurations of four 20mm were tried. Throw weight per second increased 50% but with a reduction of firing time to 5.13 seconds. Normal armament (4+1) of P-38F is 40 seconds. (note this conflicts with Dean but Dean did not give a model letter designation)

They also tested a proposed nose of four .50s and two 20mms that increased throw weight per second by 35% but this was using a P-38 as a test bed for the XP-49. Page 87 has a photograph of this arrangement. The photo’s caption also mentions the fitting of eight 50s and another fitting of three .60s. There is no mention of actual loading of ammunition and firing from the P-38, but the larger XP-49 would have 500 rpg of .50 and 90 rpg of 20mm.

End of summary of Bodie paragraphs.

The .60 caliber was a 20mm cartridge necked down to .60 caliber, which was a dumb idea. This arrangement indicates that three 20mm with sufficient ammunition may have been possible. There is no text indicating if six, let alone eight .50s could have been supplied with sufficient ammunition for a firing time equal to a fighter with six or eight wing guns. I think it is doubtful they could. I still think all things considered that four .50s (with a longer firing time) or five .50s (7.95 throw weight per second) for the P-38 would when all things are considered be effectively equal to the 4 +1 in destroying aircraft. It would have reduced logistical requirements and ultimately been a more efficient weapons package for the P-38. For whatever reason they stuck to the 4+1 even when having the possible heavier throw weight of four 20mms or six .50s. I’ll bet firing time was a factor in this decision, not just change of production issues. - Lighthunmust 

P.S. Fighter pilots miss more often than hit. Fighter pilots are more often targets than shooters.


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## Shortround6 (May 29, 2011)

the US navy figured that one 20mm gun was worth three .50 calibers in effectiveness. The throw weight works just fine if you are firing solid (non-exploding) projectiles. Relative effectiveness changed back and forth a bit as the war went one because ammo did not stay the same. Neither the 20mm Hispano or the .50 cal in aircraft use finished the war using the same ammo they started with. Effectiveness in combat reports will vary from year to year depending on ammo. The US didn't get really good .50cal ammo (the M8 API) until 1943 and it wasn't the predominate round until sometime in 1944. 

The Germans figured fighter pilots hit, on average, with about 2% of their rounds fired. I repeat, ON AVERAGE. This includes super aces, who do much better, and green pilots, who do much worse. The bigger guns ammo is much more destructive on a weight for weight basis, which is why the Germans shifted to the 30mm guns. It was almost impossible for a single engined fighter to carry enough 20mm ammo to "average" one kill per flight against 4 engined bombers. It was possible using 30mm ammo. 
It is the same principle with the.50 cal vs 20mm. 
The 20mm round may be 4 times as effective as the .50 cal round. the 3 times as effective for the gun's rating takes into account the rates of fire between the guns. The 20mm ammo is only a bit over double the weight of the .50cal ammo. 
3-5 hits from a 20mm gun may be enough (on average) to bring down a single engine fighter. How many hits does the .50 need, on average? 

By the way. the .60 caliber was an attempt at higher muzzle velocity. Studies and calculations had shown the US Army that increasing the velocity would greatly increase the chances of hitting. This a good idea on the face, the "dumb" part is that such ultra high velocity guns are heavy and require heavy ammunition. They also suffer from extreme barrel wear.


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## pinsog (May 29, 2011)

Shortround6,
"3-5 hits from a 20mm gun may be enough (on average) to bring down a single engine fighter. How many hits does the .50 need, on average"

Depends on where you hit them. Everyone speaks of how much more damage a 20mm does than a 50, but would someone please point out a safe place on a single engine fighter like the Zero, ME109 or FW190 that could absorb a 2 second burst from 4 concentrated 50's? If you hit a Zero, ME109 or FW 190 anywhere between the prop hub, 2 feet behind the pilot and between the swastikas on the wings with a solid burst from 4 concentrated 50's in the nose of a P38, i would think it is a done deal. Your either gonna kill the engine, pilot, tear off a wing, flame a fuel tank, blow up ammo in the wing, or cause some sort of massive structural failure.


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## P-40K-5 (May 29, 2011)

2 seconds of accurate fire will bring down almost any fighter. the trick is trying to get that accurate burst.

Erich Hartmann a few others mastered that trick.

anyways, a few hits from a 109 cannon was enough to bring down a fighter. that means less time shooting
at the e/a, which means more time to engage the next target, watch your back, or get the hell out of there.


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## Lighthunmust (May 29, 2011)

Shortround6 said:


> the US navy figured that one 20mm gun was worth three .50 calibers in effectiveness. The throw weight works just fine if you are firing solid (non-exploding) projectiles. Relative effectiveness changed back and forth a bit as the war went one because ammo did not stay the same. Neither the 20mm Hispano or the .50 cal in aircraft use finished the war using the same ammo they started with. Effectiveness in combat reports will vary from year to year depending on ammo. The US didn't get really good .50cal ammo (the M8 API) until 1943 and it wasn't the predominate round until sometime in 1944.
> 
> The Germans figured fighter pilots hit, on average, with about 2% of their rounds fired. I repeat, ON AVERAGE. This includes super aces, who do much better, and green pilots, who do much worse. The bigger guns ammo is much more destructive on a weight for weight basis, which is why the Germans shifted to the 30mm guns. It was almost impossible for a single engined fighter to carry enough 20mm ammo to "average" one kill per flight against 4 engined bombers. It was possible using 30mm ammo.
> It is the same principle with the.50 cal vs 20mm.
> ...


 
The USN experience with and rationale for 20mm is primarily based on ship-borne AA defense gunners. These gunners would be expected to open fire at distances much greater the typical 200 yards of effective air to air accuracy. They could do this effectively because their ammunition did not rely on kinetic energy.

The German data is primarily based on the need to shoot down U.S. Heavy Bombers. They came to the conclusion that just having the cannon was not enough because they could not carry enough 20mm or 30mm in their 109s and 190s. Hence the effort to design single engine aircraft with more ammunition capacity or/and bigger cannon. They never went down the other path of more HMG and ammunition and that may be because the 109 and 190 could not efficiently do this. The Germans were also looking at the issue with regard to standoff range for twin-engined bomber destroyers staying out of the range of American .50s.

It can take only one hit from a .50 to kill or incapacitate the pilot or engine. Erich Hartmann's “Stick your nose in his cockpit” is not so much a trick to master as having the resolve to close with the enemy because of limited ammunition for taking low hit probability shots at greater distances. Robert Johnson’s P-47 was hit with multiple 20mm shells. The last 190 to attack him was out of cannon shells and ineffective. Just a change to one cowl mounted 12.7mm for the two 7.92s would have probably end Johnson’s career.

The USAAF could have retained 20mms in the Mustang and put them in the Thunderbolt. They didn’t. They also started out with .50s in the F-80, F-84, and F86. Only the ineffectiveness due to insufficient oxygen at Korean War altitudes, better fire controls, increased aircraft size, and better quality cannons forced a change.

The .60 was a dumb idea for the reasons you stated and other reasons. As you yourself have said in other words elsewhere, “flat shooting” trajectories were over-rated for the ranges of engagement. I have as many books on firearms as aircraft. Have reloaded ammunition for accuracy, shot competition, and have experience with automatic weapons domestic and foreign up to a four 12.7mm Dshk mounted antiaircraft system. What I don’t have is the loose government money available in WW2 to be thrown at every poorly conceived (dumb) idea. The .60 was like the .220 Swift in a world where the more efficient .22-250 and .243 prevail.

Getting back to the main point: for the P-38, disregarding other fighters, the cannon may have not been the best answer.


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## P-40K-5 (May 29, 2011)

yep Erich's sticking his nose into the cockpit got him the highest kills in aviation history.. that nobody will
ever touch. nice trick indeed.


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## Lighthunmust (May 29, 2011)

P-40K-5 said:


> yep Erich's sticking his nose into the cockpit got him the highest kills in aviation history.. that nobody will
> ever touch. nice trick indeed.


 
A "trick" others on both sides were aware of. A target rich environment of lessor opponents and lack of pilot rotation is the biggest reason for the kill count.


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## P-40K-5 (May 29, 2011)

Lighthunmust said:


> A "trick" others on both sides were aware of. A target rich environment of lessor opponents and lack of pilot rotation is the biggest reason for the kill count.


two fold.. he never lost a wingman.. nutter nice trick. he also let his wingman fly his personal a/c.. etc.,etc.,etc.
target rich enviroment means that theres that many more e/a hunting for him too.. so that arguement dosn't
fly in my book. he also refused to fly any other a/c.


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## Jabberwocky (May 29, 2011)

Lighthunmust said:


> I stopped being lazy. I broke out Dean and Bodie.
> 
> The .60 caliber was a 20mm cartridge necked down to .60 caliber, which was a dumb idea. This arrangement indicates that three 20mm with sufficient ammunition may have been possible.


 
Just a small correction.

There were two wartime .60 cal experimental aircraft guns in the US.

One, the T18, was based on the Hispano, but it considered too much work to get it right. It was dropped pretty early on - 1942 I think

The other was loosely based on the German MG151/15 (15 x 96 mm). This was necked out to accept the US experimental 15.2 x 114 anti-tank cartridge and went through several iterations. 

It was never really successful. RoF and M/V were good, but the weapon was considered too heavy and not reliable enough. Despite an order for 3000 guns, only 300 were made and it and was dropped after about 10 years of messing about with various experimental designs.


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## Lighthunmust (May 29, 2011)

Jabberwocky said:


> Just a small correction.
> 
> There were two wartime .60 cal experimental aircraft guns in the US.
> 
> ...



You are absolutely correct! It has been a while since I looked at "Flying Guns, World War II" by Williams and Gustin. I forgot about the MG151 based T17. The main point I am trying to make is for the technology of the day, you reached a point of diminishing satisfactory returns past the .50 until you reached 20mm. Since the 1980s there have been .50 projectiles that approach the terminal ballistics of WW2 era 20mm cannon shells. Everyone (especially Americans) should take a look at "Flying Guns". Americans will discover they do not have a monopoly on the world's greatest geniuses for gun and projectile design.

P.S. While "Flying Guns" does discuss and has tables of comparative cartridge destructiveness, and gun power and efficiency; I do not recall a comparative discussion or table of actual ffectiveness of the aircraft carrying these guns that includes ammunition firing times available. I will look more closely for this.

P.P.S. I found no discussion or tables of actual effectiveness of aircraft in regard to ammunition firing times. Except for the ineffectiveness of firing great quantities of rifle caliber ammunition. I did find comment about both sides during the war believing they had gun effectiveness problems.


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## gjs238 (May 31, 2011)

Any stats on actual P-38 cannon vs. MG usage and results?
Anecdotal from P-38 pilots?


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## Lighthunmust (May 31, 2011)

gjs238 said:


> Any stats on actual P-38 cannon vs. MG usage and results?
> Anecdotal from P-38 pilots?



I'll take a look in my library when I can. It may take awhile as I am researching two other topics.


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## pinsog (Jun 2, 2011)

Back on thread, does anyone here think that 4 concentrated 50's would not be able to do the job against either German or Japanese fighters?


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## Shortround6 (Jun 2, 2011)

the problem with 4 concentrated .50's is that they are not laser beams with automatic tracking. If the firing plane is doing 300mph it is doing 440 fps. if the guns are firing at 13rps then the firing plane has moved over 33 ft between consecutive shots from the same barrel. If the target plane is doing 300mph it has also moved 33ft between shots. If either plane is going faster the spacing gets worse. This is assuming that the guns are fastened down to a structure with absolutely no flex whatsoever and ammo and gun have zero dispersion. If you fly a small plane like a 109 at a 90 degree path to the to the 4 gun battery and the 4 gun battery makes no tempt to track the target at speeds in excess of 300mph the 4 gun battery will put a maximum of 4 bullets into the target and a possible minimum of zero hits. 
4 concentrated .50's are better than two pairs mounted out in the wings but you still have to keep the target aircraft, not just in the sight but at the proper point in relation to the sight/aiming mark. A lot easier with the later Gyro sights. 

The four .50's could do the job. You can also dig a house foundation with hand shovels. There were better tools for both jobs.


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## Rivet (Jun 2, 2011)

"In 1937 just which B-17 equivalent should they have been planning to shoot down?" The only planes I know of during the period were the German Dornier and Junkers heavy developments that were cancelled by Goering's order in April of 1937. Perhaps memories of Italian large Flying Boats crossing the Atlantic, or the three-engined aircraft troubling African targets during the period. Regards


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## Lighthunmust (Jun 2, 2011)

pinsog said:


> Back on thread, does anyone here think that 4 concentrated 50's would not be able to do the job against either German or Japanese fighters?




I cannot find documentation, but Richard Bong was probably out of 20mm ammunition when he made his first kill. In the engagement he fired at several aircraft, and admitted missing. Bong mentions being in engagements when long bursts were fired when attempting deflection shots. Most of my reading on the subject of bursts fired in WW2 air to air engagements suggests average bursts were 2-3 seconds. Assuming 5-6 seconds being significantly long enough to perceive as a “long burst”; a third of the 20mm ammunition is gone in one burst. Bong commented that he was not a good shot on his first tour. Perhaps a significant number of his victories were achieved with just four .50s firing. One interesting statement I read was that Bong was uncanny in being in the right place to find opponents because many pilots flew many patrols without making contact. I will keep looking for documentation on expenditure of ammunition in combat and better documentation on Bong's and other pilots engagements. I'll look at my book on McGuire next.

Regarding alternate armament for the P-38: As mentioned in a previous post I made, experiments were conducted. Six and Eight gun noses were built. This may or may not be because of dissatisfaction with the 4+1 standard armament. I have found sources of complaint about the U.S. version of the 20mm HS Cannon due to improper manufacture and logistical support requirements. There is a photo in “Aircraft in Profile” V5 of a P-38L with eight .50s in the nose and two twin .50 underwing pods. This version may be intended for ground support, I doubt anyone thought it necessary for air to air.

I would not be surprised to learn that pilots did not refuse to fly with only the .50s operable in a P-38. My personal preference would be for a fifth .50 and all the ammunition space allowed with the removal of the the 20mm ammunition box. Some F4F-4 pilots apparently had enough confidence in four .50s to switched off the outboard a two .50s before engagement. They must of believe they would still be sufficiently effective with two .50s after the four were out of ammunition.


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## pinsog (Jun 2, 2011)

Shortround6 said:


> the problem with 4 concentrated .50's is that they are not laser beams with automatic tracking. If the firing plane is doing 300mph it is doing 440 fps. if the guns are firing at 13rps then the firing plane has moved over 33 ft between consecutive shots from the same barrel. If the target plane is doing 300mph it has also moved 33ft between shots. If either plane is going faster the spacing gets worse. This is assuming that the guns are fastened down to a structure with absolutely no flex whatsoever and ammo and gun have zero dispersion. If you fly a small plane like a 109 at a 90 degree path to the to the 4 gun battery and the 4 gun battery makes no tempt to track the target at speeds in excess of 300mph the 4 gun battery will put a maximum of 4 bullets into the target and a possible minimum of zero hits.
> 4 concentrated .50's are better than two pairs mounted out in the wings but you still have to keep the target aircraft, not just in the sight but at the proper point in relation to the sight/aiming mark. A lot easier with the later Gyro sights.
> 
> The four .50's could do the job. You can also dig a house foundation with hand shovels. There were better tools for both jobs.


 
Everything you just said applies to any weapon, on any fighter, from any side during WW2. Use your same formula but use a B25 with 12 fixed forward firing 50's, you will put a maximum of 12 rounds on target and a minimum of 0. Even M61 Vulcan cannon don't match up well with your formula.


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## Shortround6 (Jun 2, 2011)

Rivet said:


> "In 1937 just which B-17 equivalent should they have been planning to shoot down?" The only planes I know of during the period were the German Dornier and Junkers heavy developments that were cancelled by Goering's order in April of 1937. Perhaps memories of Italian large Flying Boats crossing the Atlantic, or the three-engined aircraft troubling African targets during the period. Regards



The Americans had built the XB-15 bomber and were working on the XB-19 in addition to a couple of preliminary designs and wooden mock-ups to the original specification for a bomber to carry a 2000lb bomb load 5000miles. The Americans probably had a better idea than anybody what size bomber would be needed for intercontinental flights and what type of construction would be needed.


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## Lighthunmust (Jun 2, 2011)

Shortround6 said:


> The Americans had built the XB-15 bomber and were working on the XB-19 in addition to a couple of preliminary designs and wooden mock-ups to the original specification for a bomber to carry a 2000lb bomb load 5000miles. The Americans probably had a better idea than anybody what size bomber would be needed for intercontinental flights and what type of construction would be needed.


 
All thanks to the “Bomber Mafia” that ruled the USAAF. Of course an argument could be made that the “Bomber Mafia” was also one of the worst enemies of the long range heavy bomber.


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## Jabberwocky (Jun 3, 2011)

Just some more information on the reliability of the Hispano. The gun achieved a reliability rate of about one stoppage every 1500 rounds in RAF service by 1943. However, in dusty conditions, such as Africa, Malta and Australia, this could be more than halved. The RAAF found to their horror that their Hispanos were jamming every 90 rounds in 1943 over Darwin. A major part of the problem was that their Spitfires were delivered without heating ducts for the gun bays, while some with the ducts were prone to breaking!


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## Lighthunmust (Jun 3, 2011)

Jabberwocky said:


> Just some more information on the reliability of the Hispano. The gun achieved a reliability rate of about one stoppage every 1500 rounds in RAF service by 1943. However, in dusty conditions, such as Africa, Malta and Australia, this could be more than halved. The RAAF found to their horror that their Hispanos were jamming every 90 rounds in 1943 over Darwin. A major part of the problem was that their Spitfires were delivered without heating ducts for the gun bays, while some with the ducts were prone to breaking!



The redundancy of a greater number of HMG has some advantages. Not that it can't also have issues with installation, but the M2 has a reputation of reliability that few other automatic weapons can match.


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## Jabberwocky (Jun 4, 2011)

That reputation was not undeserved, but reliability could vary by more than a factor of three, depending on the aircraft and installation. 

Nose installations were generally the most reliable. Wing installations less so, notably in the P-51 B/C, but the RAAF also had problems with stoppages in their Beaufighters. Both problems are best attributed to the feed arrangement, rather than the weapon itself. 

Spitfire Mk VCs also traced much of their cannon problems to the belt mechanism, a problem not suffered with the earlier snail magazine. Changes to the mechanism, then - somewhat ironically, given the US reliability problems with the Hispano - switching to a US developed belt feeding mechanism improved reliability.


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## fastmongrel (Jun 4, 2011)

Jabberwocky said:


> Spitfire Mk VCs also traced much of their cannon problems to the belt mechanism, a problem not suffered with the earlier snail magazine. Changes to the mechanism, then - somewhat ironically, given the US reliability problems with the Hispano - switching to a US developed belt feeding mechanism improved reliability.



The Spitfire VC had a Martin Baker belt feed mechanism. Martin Baker is a British company.


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## Shortround6 (Jun 4, 2011)

We are trying to come up with the reliability of two weapons that were not only installed in a variety of aircraft in a number of different ways but also, in the case of the Hispano, used different feed mechanisms and was made to different standards in the two major countries that used it. 
The Browning .50, while it obviously is a classic that has endured for many, many years was also made for quite a number of years and was used in a number of ways, not all combinations exhibit the same reliability. 

As for the Hispano, it needed a rigid mounting, not always easy to achieve in wings compared to fuselage mounts. It did not take kindly to being turned 90 degrees on it's side with it's drum in early Spitfire installations. Both experimental MK I and early MK Vs. It didn't tolerate cold as well as the Browning and yes it needed more (better) maintenance. Things did get better as the war went on, as experience mounted, both maintenance and installation knowledge built up. This for British guns, the American insistence on excessive head space in the chamber specifications doomed the American guns to a history of trouble. 

However the same can be said of the Browning, What is a reliable gun on a test stand at sea level in relatively warm weather (even 0 degrees beats -40) may not be so reliable at 25,000ft in a 3 "G" turn. What is a reliable gun chugging away at 450-550rpm on a ground mount may not be so reliable trying to do 800-850rpm pulling that heavy belt from a number of feet away. 
A lot of the early installations of the Browning gave trouble and were less than satisfactory. Again, as time went on and experience was gained the situation improved. 
The Browning probably always had an edge in average reliability in aircraft use. The amount of this margin or edge may have changed with both time and specific installations.


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## Rivet (Jun 4, 2011)

I'm partial to the work of those folks from Utah, myself. The M2 .50 Caliber Recoil Operated Machine Gun would have been my choice for primary armament for the P-38, four of em, mounted as tight to the centerline as would be possible.

Little Story:
John Moses Browning was on the range early in Aberdeen, Maryland the day World War I ended. With him, in answer to a military contract, he had his prototype of his requested .50 Caliber fully automatic rifle. Having no purpose built mount for the weapon Browning used a .30 Caliber tripod. Browning set up the gun on the range, sat behind it, opened the breech and poured the contents of a paper bag he produced from his jacket pocket into it. When questioned as to the contents of the bag by accompanying ordnance officers he replied, "Sand. If it does not take this what good is it?" A ten round belt of newly made cartridges was loaded. The weapon functioned through the ten round burst, Browning getting a jack-rabbit ride on the light mount.

"The Browning probably always had an edge in average reliability in aircraft use. The amount of this margin or edge may have changed with both time and specific installations. "

Material specifications changes.


I'd seen a few posts in here decrying the terminal effectiveness of the .50 Cal. M-2 vs. 20mm. Friend, I am fair confident that the 750 grain pill delivered by the M-2 is capable of taking apart most anything put in its way, with the benefit of being able to carry more of them than the larger rounds.
Regards


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## Lighthunmust (Jun 4, 2011)

Rivet said:


> I'm partial to the work of those folks from Utah, myself. The M2 .50 Caliber Recoil Operated Machine Gun would have been my choice for primary armament for the P-38, four of em, mounted as tight to the centerline as would be possible.
> 
> Little Story:
> John Moses Browning was on the range early in Aberdeen, Maryland the day World War I ended. With him, in answer to a military contract, he had his prototype of his requested .50 Caliber fully automatic rifle. Having no purpose built mount for the weapon Browning used a .30 Caliber tripod. Browning set up the gun on the range, sat behind it, opened the breech and poured the contents of a paper bag he produced from his jacket pocket into it. When questioned as to the contents of the bag by accompanying ordnance officers he replied, "Sand. If it does not take this what good is it?" A ten round belt of newly made cartridges was loaded. The weapon functioned through the ten round burst, Browning getting a jack-rabbit ride on the light mount.
> ...






Rivet said:


> I'm partial to the work of those folks from Utah, myself. The M2 .50 Caliber Recoil Operated Machine Gun would have been my choice for primary armament for the P-38, four of em, mounted as tight to the centerline as would be possible.
> 
> Little Story:
> John Moses Browning was on the range early in Aberdeen, Maryland the day World War I ended. With him, in answer to a military contract, he had his prototype of his requested .50 Caliber fully automatic rifle. Having no purpose built mount for the weapon Browning used a .30 Caliber tripod. Browning set up the gun on the range, sat behind it, opened the breech and poured the contents of a paper bag he produced from his jacket pocket into it. When questioned as to the contents of the bag by accompanying ordnance officers he replied, "Sand. If it does not take this what good is it?" A ten round belt of newly made cartridges was loaded. The weapon functioned through the ten round burst, Browning getting a jack-rabbit ride on the light mount.
> ...



Rivet,

I have not been a member of this forum for even a month. From what I have read you and I seem to be in the minority regarding the effectiveness of the M2 for WW2 aerial combat. No doubt the cannon has the edge in individual projectile power, but there are many other factors involved. I am researching just how much the MG<Cannon gap really was. So far I believe it looks large in tables and graphs of projectile power and individual weapon cyclic rates, and not so much in actual use. Part of the problem is we don't have many reports of 6/8 gun American fighters attempting to shoot down strongly build, heavily armed, four engined bombers. I wonder why? What I am finding is German accounts of shooting down bombers in one firing pass being atypical. It taking multiple firing passes to force bombers out of formation and then finishing them off. I am finding accounts of the Germans believing hits from twenty 20mm shells or three 30mm shells being necessary to destroy a heavy bomber. I also find accounts of Germans having a 2-4% hit percentage. Sources claim that some of the German cannons equal the cyclic rates of the M2. One of these source usually lists a single rate for the cannons, but a slow and fast rate for the M2. This makes we wonder about a level playing field of primary sources and testing. I am still working on determining what the balance point is between weapons with smaller amounts of devastating projectile power and weapons with larger amounts of sufficient projectile power. To the best of my knowledge, no one has address the actual firing reliabilty of the German cannons or the engagement times of single engine fighters attacking the bombers. I don't consider those over loaded FW190s fighters, they were bomber destroyers and sitting ducks for true fighters. Consider this; would the P-38 mock-up with 12 .50s been an even better bomber destroyer than the cannon armed FW190? It also would cease to be a fighter and become a sitting duck. I have actually fired and M2s and a Dshk, and seen upclose the what hits from .50s and 20mms do to lightly armored targets. The .50s destroyed the targets ability to function, the 20mms destroyed the target. The 20mms did it from the altitude of an AC-130, the .50s from 1000 yards. Either results in a kill if the targets were flying at 20,000 feet. WW2 aerial air to air engagements were rarely more than half of a 1000yards. 

Of course installation and environment affected M2 functioning, but I suspect that all those wonderful cannons were much more adversely affected as were the aircraft that mounted them. Here is an example: It is my understanding that on one of the late mark Spitfires they had to remove two of the four 20mms and replace them with .50s because of aircraft flight handling issues. I'm sure shortround6 can find the details faster than I can. He has an amazing ability to post detailed specifications and dates of events. I am wondering about him being a professional aviation writer or some kind of aviation savant. I suspect he has a very good idea of what a .50cal projectile can do.


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## tomo pauk (Jun 4, 2011)

The 'pill' from .50cal can surely kill - providing it can hit the thing that can be killed. 3 or 4 dozens of rounds piercing wing skin don't kill, they just pierce the skin. Compare that with one or two dozens of cannon shells hitting the wing - each shell makes a neat hole (foot or two in diameter, depending on size construction of shell).


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## Lighthunmust (Jun 4, 2011)

tomo pauk said:


> The 'pill' from .50cal can surely kill - providing it can hit the thing that can be killed. 3 or 4 dozens of rounds piercing wing skin don't kill, they just pierce the skin. Compare that with one or two dozens of cannon shells hitting the wing - each shell makes a neat hole (foot or two in diameter, depending on size construction of shell).


 
No one disputes this. But what you wrote is far from a complete answer to the question of actual effectiveness in WW2. 1 or 2 dozens of cannon shells? How many firing passes at 2-4% hit rates does that require from a single engine fighter. One .50cal bullet can kill an engine, or reduce its power enough to impede the bombers ability to remain in formation.


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## tomo pauk (Jun 4, 2011)

> 1 or 2 dozens of cannon shells? How many firing passes at 2-4% hit rates does that require from a single engine fighter.



How many passes would've required 3-4 dozens of .50cal ammo?



> One .50cal bullet can kill an engine, or reduce its power enough to impede the bombers ability to remain in formation.



The air force that was under hell of a pressure to stop a major bomber offensive concluded that smaller number of cannons were better bet than large number of HMGs. I tend to agree with them.


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## Lighthunmust (Jun 4, 2011)

tomo pauk said:


> How many passes would've required 3-4 dozens of .50cal ammo?
> 
> 
> 
> The air force that was under hell of a pressure to stop a major bomber offensive concluded that smaller number of cannons were better bet than large number of HMGs. I tend to agree with them.


 

It is your assumption that 3-4 dozens of .50cal ammo would be needed. It would take me a great amount of time to calculate number of firing passes due to different armament packages on different fighters.

Even if the Luftwaffe had decided the other way, they probably had no real choice but to go with the cannons. Resource availability and aircraft platform armament flexibility are factors to consider. Do we really know if an aircraft armament package of HMG could not be designed where all factors of firepower would be as or more effective than a cannon package for the fighters of WW2?


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## Rivet (Jun 4, 2011)

"How many passes would've required 3-4 dozens of .50cal ammo?"

You'd have 6.1 seconds of firing time to expend the low end of 36 rounds (3 Dozen) from one M-2 Browning set to fire at 400 r.p.m. Regards


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## tomo pauk (Jun 4, 2011)

Lighthunmust said:


> It is your assumption that 3-4 dozens of .50cal ammo would be needed. It would take me a great amount of time to calculate number of firing passes due to different armament packages on different fighters.



We can assume what we want. Assuming that it would've taken _less_ hits by a projectile of far lower destruction power is not something I'd agree, however. Hence my 3-4 dozens of .50 cal ammo assumption.
If you want to calculate stuff, perhaps 5 x .50cals for Bf-109Gs and 6 .50cals for Fw-190 might be a good starting point. 2 HMGs synchronized for 109, 4 for 190.



> Even if the Luftwaffe had decided the other way, they probably had no real choice but to go with the cannons. Resource availability and aircraft platform armament flexibility are factors to consider. Do we really know if an aircraft armament package of HMG could not be designed where all factors of firepower would be as or more effective than a cannon package for the fighters of WW2?



You'll have to dig further about that. 
For real air forces, RAF, VVS, LW, IJA/IJN, RA (even USN) went for 20mm (and/or above) as WW2 dragged towards end, while USAAC remained mostly with HMG. so I'd conclude that cannon was seen as a more viable weapon.


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## Lighthunmust (Jun 4, 2011)

Rivet said:


> "How many passes would've required 3-4 dozens of .50cal ammo?"
> 
> You'd have 6.1 seconds of firing time to expend the low end of 36 rounds (3 Dozen) from one M-2 Browning set to fire at 400 r.p.m. Regards




This is a really complex issue. It will take a great amount of research time to adequately find answer. A couple of things though: 400 rpm per M2 seems a bit low, firing time for a frontal attack is 1.5 seconds according to Mike Spike's diagram and text, number of guns firing, what methodology did the LW use to determine hit percentage and specifically did they include all angles of attack to derive this number, etc.


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## Shortround6 (Jun 5, 2011)

Lighthunmust said:


> So far I believe it looks large in tables and graphs of projectile power and individual weapon cyclic rates, and not so much in actual use. Part of the problem is we don't have many reports of 6/8 gun American fighters attempting to shoot down strongly build, heavily armed, four engined bombers. I wonder why? What I am finding is German accounts of shooting down bombers in one firing pass being atypical. It taking multiple firing passes to force bombers out of formation and then finishing them off. I am finding accounts of the Germans believing hits from twenty 20mm shells or three 30mm shells being necessary to destroy a heavy bomber. I also find accounts of Germans having a 2-4% hit percentage. Sources claim that some of the German cannons equal the cyclic rates of the M2. One of these source usually lists a single rate for the cannons, but a slow and fast rate for the M2. This makes we wonder about a level playing field of primary sources and testing. I am still working on determining what the balance point is between weapons with smaller amounts of devastating projectile power and weapons with larger amounts of sufficient projectile power. To the best of my knowledge, no one has address the actual firing reliabilty of the German cannons or the engagement times of single engine fighters attacking the bombers. I don't consider those over loaded FW190s fighters, they were bomber destroyers and sitting ducks for true fighters. Consider this; would the P-38 mock-up with 12 .50s been an even better bomber destroyer than the cannon armed FW190? It also would cease to be a fighter and become a sitting duck. I have actually fired and M2s and a Dshk, and seen upclose the what hits from .50s and 20mms do to lightly armored targets. The .50s destroyed the targets ability to function, the 20mms destroyed the target. The 20mms did it from the altitude of an AC-130, the .50s from 1000 yards. Either results in a kill if the targets were flying at 20,000 feet. WW2 aerial air to air engagements were rarely more than half of a 1000yards.
> 
> Of course installation and environment affected M2 functioning, but I suspect that all those wonderful cannons were much more adversely affected as were the aircraft that mounted them. Here is an example: It is my understanding that on one of the late mark Spitfires they had to remove two of the four 20mms and replace them with .50s because of aircraft flight handling issues. I'm sure shortround6 can find the details faster than I can. He has an amazing ability to post detailed specifications and dates of events. I am wondering about him being a professional aviation writer or some kind of aviation savant. I suspect he has a very good idea of what a .50cal projectile can do.



First, let me thank yo for the kind words. I just have done some reading and collecting of books on few subjects like guns and engines, There are many people on this Forum whose knowledge in many areas of WW II aircraft far exceeds mine. 

Back to the subject at hand. 
There is no question that the .50 is a very powerful round compared to what most of have had any experience with. It is roughly 4 time more powerful than a .30-06

There is no question that it can do a lot more damage than rifle caliber rounds to armor, masonry walls, trees engine blocks,etc. the problem with comparing it to "THE" 20mm is "WHICH" 20mm are you comparing it to and how?

A short and abbreviated list of muzzle energy in Joules, courtesy of Tony William's book "Flying Guns World War II".

RiflecaliberMGs.........................3,270-4,140
Italian/IJA 12.7........................10,600
American .50...........................17,400
Russian 12.7............................19,200
German 13................................9,700
IJN 20 type 99-1.......................23.000
German 20 FF..........................19,700-24,100
German 20/151........................29,000-29,400
IJA HO-5 20.............................21,000-29,000
Russian 20..............................36,000
IJN type 99-2...........................36,000
Hispano 20..............................46,900-50,300
German 20 X 138.....................60,500

Again this is kinetic energy at the muzzle. Some projectiles could loose up to 38% of their velocity by the time they traveled 300 meters depending on type and shape. The .50 was very good in this regard being among the best if not "THE" best at retaining velocity. From a pure 'striking' power with kinetic energy at normal combat ranges (1000yd shots are best left to flight simulation games) the .50 actually compares rather well with some 20mm rounds. Especially considering rates of fire. How much energy can be delivered per second?
However we can also see that the Hispano was practically in a class by itself, being about 30% more powerful than any other commonly used aircraft 20mm gun. The German 20 X 138 was an anti-aircraft/tank/anti-tank round that was only used in a small run of heavy-slow firing aircraft guns in the late 30s. The Hispano has almost 3 times the kinetic energy of the .50 cal and so is going to do that much better at smashing engines, breaking ribs, spars, attachment flanges,etc. 
Of course this is with solid shot (which the British did use when they had problems with early fuses) and does not consider the dynamic of the HE filler. 

With the He (or HE+incendiary) we have 3 things to consider that the .50 essentially skips. 
1. The amount of HE filler, which varied from 3.7 grams to about 10 grams for most shells with the German M-Geschoss jumping to 20 grams and above.
2. The fusing. does it allow the shell to penetrate or does it blow up on contact, making an impressive hole on the skin but not damaging the internal vital parts of the aircraft.
3. The fragmentation of the 20mm projectile. A German 'mine' shell weighed 92 grams with 20 of that being the HE, take out the weight of the fuse and there isn't a lot of metal to turn into fragments that can cut/pierce nearby wires/lines/cables. Japanese Army 20mm projectiles weighed 79 grams with about 8-12 grams of filler and were in the same boat. Heavier (127-130 gram) projectiles with around 10 grams of filler have a lot more metal flying around after the explosion to cause secondary damage, even if only a few feet from the explosion site. 
3-A. Light 20mm shells with high HE content don't penetrate very well. While a heavy shell with thick walls 'can' be fused to penetrate heavy structure or light armor and detonate behind it, a thin wall shell will breakup and fail to penetrate regardless of the fuse. 

As can be seen trying to compare the .50cal to 20mm guns is very difficult because of the variety of 20mm rounds and ammunition. 

And we haven't even gotten to the rates of fire and guns weights yet


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## Rivet (Jun 5, 2011)

"400 rpm per M2 seems a bit low"

This in the interest of accuracy. Much to be said for a weight of fire on target, not having to fight the recoil increases ability to aim.


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## Shortround6 (Jun 5, 2011)

Rivet said:


> "400 rpm per M2 seems a bit low"
> 
> This in the interest of accuracy. Much to be said for a weight of fire on target, not having to fight the recoil increases ability to aim.




Ah, isn't the gun bolted to the airframe in some fashion? Fighting the recoil might only apply to a hand aimed gun like a piviot mount on a jeep or a waist gun. If firing at 800rpm throws the aim off that much in a fixed gun you need a new airplane. 

That said some early war .50s did cycle at about 400rpm in synchronized installations. But that has to do with starting with a 600rpm gun, adding the synchronizers and figuring in belt drag.


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## johnbr (Jun 6, 2011)

How about the 6 Mauser 215 guns in the P38.


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## gjs238 (Jun 7, 2011)

Lighthunmust said:


> I am still working on determining what the balance point is between weapons with smaller amounts of devastating projectile power and weapons with larger amounts of sufficient projectile power.



Kinda like the .308/M-14 vs. .223/M16 debate that's been raging for decades.


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## renrich (Jun 7, 2011)

This is a highly interesting debate. Good work by many. All along I have been an advocate of " Old Ma Deuce" perhaps because I fired one on the range at Fort Hood and saw what it could do to old deuce and a halfs and half tracks. Does anyone believe that any WW2 aircraft was built more solidly than those vehicles?

Having said that, I realise that the USN, on their ships, started the war with a lot of fifties in their AA suites and quickly substituted 20 mms and 40 mms for those fifties. They did that because they needed to knock down the attackers now. One factor in those cases was that the shots were usually head on or deflection shots, not from the rear aspect like most aviation kills. That factor raises an interesting question which I don't have the answer for.

When hunters are after dangerous large thick skinned game they generally use solids rather than expanding bullets because they want the projectile to penetrate deeply, maybe go through bone rather than expand quickly. Likewise fmj bullets in modern military rifle caliber bullets often zip right through the target and don't do nearly as much damage to a leg, arm or even the body as a dum dum bullet or the massive relatively blunt, lead minie ball of the War of Northern Aggression.

Here comes the question. I believe that the various cannon shells had a fuse which caused the internal explosive charge to explode when the projectile made contact with the target. Is it possible that in some cases a hit on the skin of the after fuselage of an aircraft or the skin on a wing by a cannon shell would cause the explosion which would cause a hole in that skin but perhaps no further damage where as a kinetic energy bullet like the 50 BMG would zip through the skin and continue more deeply into the fuselage or wing, possibly causing damage to a radio, oil cooler, oxygen bottle, control cable, radiator, etc. ???

Don't misconstrue what I am asking. I have no doubt that, on average, a hit from a 20mm would be more destructive than a hit from the 50 BMG but I am wondering if the destructiveness of the WW2 20mms compared to the WW2 50 BMGs might be overstated as far as air to air combat is concerned. If it is, the relative lethality of the 50 BMGs in WW2 because of number of guns carried, rate of fire, ammo carried, reliability, etc., might be much better than we realise.

Another point which I don't believe is well understood by many of us is that the way guns were bore sighted in WW2. They were not always regulated to converge on a single point at a certain range. According to pilot preference or unit policy, some were regulated to produce a "box" pattern at perhaps 300 yards, some were regulated where the inboard guns converged at a fairly close range, the middle guns further away and the outboard guns even further. The nose mounted guns of the P38 could be sighted to give a fairly wide pattern at 300 yards. I have also read that many pilots of Corsairs would turn off two guns and use the four remaining guns ammo before turning back on the other two.


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## tyrodtom (Jun 7, 2011)

If the cannon fuze can trigger the explosion even in 1/1000th of a second, the shell will have traveled maybe 2 feet before it explodes. That's if it hits something flimsy like the outer skin, if it hit any of the structual members, of course it would slow down more. In some cases the outer skin probably wouldn't even trigger the fuze.

There's a lot of variables, fuze sensitivity, and fuze initiation speed, which i'm sure they were doing a lot of experimenting on.

I was pretty involved with munitions in the mid to late 60's. But i've got a lot to learn on the WWII varietys.


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## Lighthunmust (Jun 7, 2011)

tyrodtom said:


> If the cannon fuze can trigger the explosion even in 1/1000th of a second, the shell will have traveled maybe 2 feet before it explodes. That's if it hits something flimsy like the outer skin, if it hit any of the structual members, of course it would slow down more. In some cases the outer skin probably wouldn't even trigger the fuze.
> 
> There's a lot of variables, fuze sensitivity, and fuze initiation speed, which i'm sure they were doing a lot of experimenting on.
> 
> I was pretty involved with munitions in the mid to late 60's. But i've got a lot to learn on the WWII varietys.



Another variable would be the "dud" percentage. A percentage that may climb if the living conditions of the work force decline. It is my understanding that the Germans did have the technology to fuze their 20mm and 30mm shells to perform as desired. What they needed was a good proximity fuse.


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## Shortround6 (Jun 7, 2011)

Lighthunmust said:


> Another variable would be the "dud" percentage. A percentage that may climb if the living conditions of the work force decline. It is my understanding that the Germans did have the technology to fuze their 20mm and 30mm shells to perform as desired. What they needed was a good proximity fuse.



Since it took some time into the 70s (80s?) to get a proximity fuse into a 40mm shell I think this one is a non starter for WW II aircraft cannon. 

With a blast radius measured in single digit feet (and low digits at that) Proximity fuses for 20-30mm shells are not really a worthwhile idea.


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## Readie (Jun 7, 2011)

Shortround6 said:


> Since it took some time into the 70s (80s?) to get a proximity fuse into a 40mm shell I think this one is a non starter for WW II aircraft cannon.
> 
> With a blast radius measured in single digit feet (and low digits at that) Proximity fuses for 20-30mm shells are not really a worthwhile idea.



Did Anti Aircraft shells have proximity fuses or where they triggered by attitude / time?
Cheers
John


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## Lighthunmust (Jun 7, 2011)

Shortround6 said:


> Since it took some time into the 70s (80s?) to get a proximity fuse into a 40mm shell I think this one is a non starter for WW II aircraft cannon.
> 
> With a blast radius measured in single digit feet (and low digits at that) Proximity fuses for 20-30mm shells are not really a worthwhile idea.


 


Readie said:


> Did Anti Aircraft shells have proximity fuses or where they triggered by attitude / time?
> Cheers
> John



Didn't American 40mm shipborne AA have proximity fuses? I also seem to recall American 90mm AA had them.

My understanding is that most fuses were triggered by time of flight to altitude for AA.


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## Shortround6 (Jun 7, 2011)

AA shells started with time fuses, the British were developing the proximity fuse and passed it to the US. Since it took mini-vacuum tubes (valves) and special batteries to make it work it took up a lot of volume in the shell. British and US used it in 90mm and bigger AA shells but got it into 3in/75mm by the wars end. The AA troops were not allowed to US proximity fuses where there was a chance of the Germans capturing them until sometime in 1944 when it would have been too late to copy them.


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## Shortround6 (Jun 7, 2011)

Lighthunmust said:


> Didn't American 40mm shipborne AA have proximity fuses? I also seem to recall American 90mm AA had them.
> 
> My understanding is that most fuses were triggered by time of flight to altitude for AA.


 
Maybe in the 70s or 80s the 40mm had proximity fuses.


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## Lighthunmust (Jun 7, 2011)

Shortround6 said:


> AA shells started with time fuses, the British were developing the proximity fuse and passed it to the US. Since it took mini-vacuum tubes (valves) and special batteries to make it work it took up a lot of volume in the shell. British and US used it in 90mm and bigger AA shells but got it into 3in/75mm by the wars end. The AA troops were not allowed to US proximity fuses where there was a chance of the Germans capturing them until sometime in 1944 when it would have been too late to copy them.


 


According to Wikipedia (yes I know) they were used by U.S. artillery during the Bulge. Supposedly terrified German infantry who nearly mutinied. I will do some more fact checking.


According to an article on the Naval Heritage website of the U.S.N. they successfully tested the first fuses in 1941 using among other weapons a 37mm cannon. This may or may not mean that a 40mm proximity fused shell was possible just not economical to mass produce. Gotta do some more digging.


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## Shortround6 (Jun 7, 2011)

See; http://www.history.navy.mil/faqs/faq96-1.htm

37mm gun was used to launch test components to see if they would stand the shock of firing, not with the idea of coming up with a workable projectile in that caliber.

Early proximity fuses took up enough room that some shells were provided with a removable explosive element that was taken out when the Proximity fuse was used and left in when normal time fuses were used. 

And "In addition to the development of the Mk 33 fuze for the British, another fuze known as the Mk 41 was also produced. This latter fuze was designed primarily for the British 4" gun carried aboard destroyers, and differed from the Mk 33 in that its size was still smaller. This was necessary because the 4" projectile was too small to accommodate the Mk 33 fuze and still leave sufficient quantity of explosive."

"Consequently, a Mk 45 fuze was produced for the 3"/50 in about May of 1944. This fuze was delivered to the Fleet, but was never very satisfactory and its production was ultimately discontinued. A new fuze, known as the Mk 58, was designed for the 3"/50 which contained more or less the standard Mk 45 design with the addition of a wave suppression feature to permit use of this fuze low over waves. The Mk 58 fuze was delivered to the Fleet in November 1944."


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## Lighthunmust (Jun 7, 2011)

Shortround6 I sent you a PM


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## fastmongrel (Jun 8, 2011)

Shortround I have come across some mentions of Canadian work on VT fuses but never found any details. Did the Canadians ever get a working fuse into production.


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## renrich (Jun 8, 2011)

Another example of what I am talking about is the British experience at Jutland. It is said that the relatively poor performance of the heavy caliber AP British shells compared to the German was that either because of poor fuse performance or unstable internal explosive material, the Brit APs exploded on the surface of the target's armor plate whereas the German's APs internal explosive did not detonate until after the shell penetrated inside the armor plate. An extreme example but illustrative of the factor which might hinder lethality of aerial cannon shell.


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## Lighthunmust (Jun 8, 2011)

Shortround6 said:


> See; http://www.history.navy.mil/faqs/faq96-1.htm
> 
> 37mm gun was used to launch test components to see if they would stand the shock of firing, not with the idea of coming up with a workable projectile in that caliber.



You are absolutely right! I obviously skimmed that article way to fast. The relevant passage:

"It was soon decided that the best way to test tubes and other components for ruggedness was to actually fire then from a gun and recover them to examine for extent and causes of failure. Early in 1941, experiments were carried out in which tubes were mounted in blocks in a 5"/38 projectile arranged for parachute recovery. Other means of recovery firing were also undertaken. A smooth bore gun was made out of a piece of gas pipe and set up in a farm yard for testing of tubes and components. This gun was fired vertically and the projectiles, which were homemade, fell back in the field where they could be recovered and disassembled. This gun was later superseded with an Army 37mm gun used for recovery firing.

Concurrently, circuit work was carried out in the laboratory. Also, functioning oscillators were mounted in projectiles and fired in attempts to get functioning in flight. Both the 5"/38 and the 37mm guns were used in these tests. Radio receivers were used in an attempt to hear the signal from the oscillator during flight. As a source of power for the unit in the 5"/38 projectile, special batteries built by the National Carbon Company for the bomb fuze were used. For the unit in the 37mm projectile, a special battery was built using National Carbon Company's minimax cells for B-power and pen-light cells for A-power. At about the end of April 1941, an oscillator fired in the 37mm gun was actually heard throughout flight."

Thanks for catching that Shortround6.


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## Shortround6 (Jun 8, 2011)

The British did have trouble with the Hispano shells exploding too soon but that was in 1940-41 and the problem was corrected later in the war. 

This is what makes comparing these guns rather difficult. Many guns (and their ammo) did not stay static during the 6 years of war but the guns evolved as did their ammo so a late war gun and ammo combination gave rather different results than the "same" gun at the beginning of the war. 

The American .50 got a big boost with the introduction of the M 8 API round. A combination round that combined both an AP core and a small quantity of incendiary material. Before it's introduction the Americans had to used mixed belts. Fighters used about 50/50 AP rounds and incendiary rounds with what ever percentage of tracer was in vogue at the time/place. Bombers used a much higher percentage of tracer. The AP just poked holes and the incendiary wouldn't penetrate. this M8 round was used in the big air battles over Germany in 1944 and is part of the reason that 4-6gun Mustangs did so well. If they had used the early mixed belts they would probably still have won but the margin might not have been quite the same. 
this is something to consider when people make the argument that Four .50s worked just fine over Germany in 1944 so they should have worked just fine in 1940.


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## Lighthunmust (Jun 8, 2011)

Was it really a case of the incendiary rounds not penetrating fuel tanks and lines, and AP only making holes? Wasn't more a case of doing a job with one round instead of two?


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## renrich (Jun 8, 2011)

I read in an issue of Air and Space a number of years ago an article about the BOB. I wish I had latched onto and kept the issue. There was a lot of good info. One statement they made was that it took 379 (?) hits from the 303 to bring down a German bomber. This was a calculation by the boffins before the war and the justification for the eight gun fighter. Does anyone remember that number and can verify that it is accurate? It may have been 179 but my memory says 379. This article also went into detail about how much easier it was to repair a Hurricane that had been damaged than a Spitfire, with the labor and materials that were handy.

Anyway, if those calculations were correct or even if the British believed them to be correct, it is no wonder they wanted six guns in the Wildcat. Of course the British improved the performance of the 303 bullet during the war, (DeWilde bullet?)


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## Shortround6 (Jun 8, 2011)

Lighthunmust said:


> Was it really a case of the incendiary rounds not penetrating fuel tanks and lines, and AP only making holes? Wasn't more a case of doing a job with one round instead of two?



The incendiary rounds may have penetrate fuel tanks and fuel lines but they may not have penetrated armor that well. The basic difference between M1 "ball" ammo and M2 AP was that the steel core of the M2 was of hardened steel vs the soft steel of the ball round. 

Here is a description of the M1 incendiary by Tony Williams " There was also a .50 M1 incendiary, which was a scaled-up and simplified version of the British Dixon ("De Wilde") .303. This consisted of four elements: the bullet jacket which enclosed the whole bullet except for the base; a hollow steel sleeve fitting inside the jacket for the central helf of its length; the incendiary mixture which filled all of the nose, plus the inside of the steel sleeve; and a base plug, usually of lead"

A soft steel core that is hollow isn't going to penetrate what a solid hardened core will. The M8 round used a hardened core but the incendiary material (less than 1/2 the M1) was in front of the core. While perhaps giving up little in the way of penetration it did give a bullet that was useful against most of the targets/material in an aircraft. Please note that the incendiary material was unlikely to penetrate a piece of armor or heavy structure with the core.

AP rounds are only going to poke holes. Granted they can cause leaks which something else can ignite.


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## Shortround6 (Jun 8, 2011)

renrich said:


> Anyway, if those calculations were correct or even if the British believed them to be correct, it is no wonder they wanted six guns in the Wildcat. Of course the British improved the performance of the 303 bullet during the war, (DeWilde bullet?)



And I as keep saying, in 1939 and early 1940 the .50 cycled at 600rpms not the 800-850 rpm that it cycled at in 1942. so you needed over 5 guns to equal the the rate of fire of 4 of the later guns. Since you can't mount 5 1/2 guns that meant 6 guns. Apparently the 6 gun specification was over taken by improved gun performance.


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