Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (3 Viewers)

[P-39 Expert]

Pilot reports of .50 cal API were very favorable. There were F6F's that shot down Vals with only one round.

Not a lot of room for radios in a P-39.

View attachment 595130

Radios were in the tail cone. If you remove the 100lb armor from the nose you only need to remove 100lbs from the tail. Moving the radios up to right behind the pilot/above the engine accomplished that since that was practically on the center of gravity.

This is just what I have come up with, as I said Bell managed to maintain CG when substituting the 20mm (140lbs lighter) for the 37mm cannon. I don't know exactly how they did it, but they did. In his book "Cobra", Birch Matthews mentioned that in the P-39M the nose armor was no longer needed from a balance standpoint. Since all P-39 airframes were essentially the same one would think that getting rid of that nose armor would have been relatively easy.

 

[P-39 Expert]

Ah, the wondrous American .50 cal

late war .50 about 800rpm with 43 gram bullet holding about 1 gram of incendiary material
20mm gun about 600rpm with 130 gram projectile holding 10 or more grams of incendiary or HE.

They have nearly identical muzzle velocities. The .50 has a better shaped bullet, the 20mm has more weight per unit of frontal area for better sectional density. Ballistic coefficient does favor the .50 but doesn't really come into play in an realistic air to air scenario (600 yds or under).

The M8 API was introduced in early 44. It was basically a copy of the Russian 12.7mm API round so there was no technical reason it could not have been introduced sooner for "what ifs"
However part of it's value was the incendiary ignited on impact as it was in the nose. It would give a flash on impact indicating the shooter was on target (tracer use was much diminished at this time) however very little incendiary material made it inside the aircraft if it hit anything substantial on the way in (or hit at bad angle).

I would note the examining wrecks or looking at wreck photos needs some interpretation. You can wind up with quite a bit of paint knocked off surrounding a rather small hole. You also have bullets hitting at rather oblique angles making large dents/scraps but no penetration when fired at long ranges. If you have a round "marking" then the bullet hit at a good angle, the more oval or elongated the hole/scrape the worse the angle.


and for instance.
View attachment 595131
supposed to have been shot down Friday 16th August 1940. in Scotland

.303s? AA fire? The RAF had how many 20mm armed aircraft in August of 1940 in the North of England and Scotland?

What made the bigger holes?

What is your view on the reliability of the American 20mm cannon? Supposedly it was less reliable than the British version, both copies of the same gun.

 

[Shortround6]

What is your view on the reliability of the American 20mm cannon? Supposedly it was less reliable than the British version, both copies of the same gun.

It was less reliable than the British version (Licence built) to start with as the British had modified theirs due to test results. Americans started with looser tolerances in general and a chamber about 1mm longer (?). The longer chamber allowed the cartridge to move forward when hit by the firing pin, this lead to a light primer strike and misfires. The Americans finally did get it straightened out but it took far to long. The Hispano was also sensitive to mounting, after all, it was designed to be bolted to a roughly 1000lb engine. The P-38s seem to have done OK, in part due the gun being mounted in a rather heavy cradle. Many of the wing guns (or even belly pack guns) did not get this heavy cradle.

In the US there was quite a bit of finger pointing as the gun makers blamed the ammunition makers and the ammunition makers blamed the gun makers.

However, as with with any weapon that spanned 6-7 years (first Hispano 404 cannon for the US was shipped in Feb 1938, the Americans did NOT get the Hispano from the British)
one sentence does not cover the whole situation. Four Companies built a total of 134,638 guns during WW II. after gun number 56,410 the American guns were identical to the British guns for all practical purposes. Which does leave a lot of guns in storage or out in service establishing a bad reputation. The final tally was:

The Navy got....................................21,228 guns
the Army got....................................13,272 guns
The British got..................................44,474 guns
stored:
...........Servicable...............................19,092 guns
.........UNservicable...........................35,995 guns
Lost or worn out...................................692 guns. (US service?)

By far the largest producer was Oldsmobile but even they stopped production in Feb 1944.

This is because the Americans had developed their own lightened, faster firing version called the T-31 of which 32,326 were produced by modifying most of the 35,955 AN M-2 guns held in stock as unserviceable. This started in the summer of 1944.

 

[PAT303]

The Germans replaced the .30cal MGs with the 13mm (.50 caliber) MG for their 109G-6 and 190A-6. They apparently thought the .30s were not powerful enough.

So if the .30's aren't good enough what shot down the 3,000 or so aircraft lost in the BoB, harsh language?.

 

[PAT303]

The 7x57 passed through it like it was cardboard...

I shoot cast bullets in my .303's, they go through 1/4'' steel plate at 50m easily.

 

[PAT303]

In it there are several shots of LW bomber parts being hauled off for scrap with quite a few bullet holes in them. I'll scan it and post it if I remember, but the gist of it is this, you can clearly see in the photos which holes were made by the 20mm and which dents and paint scrapings were made by the .303's.

Why would 109's shoot down their own bombers?.

 

[PAT303]

Ah, the wondrous American .50 cal

late war .50 about 800rpm with 43 gram bullet holding about 1 gram of incendiary material
20mm gun about 600rpm with 130 gram projectile holding 10 or more grams of incendiary or HE.

They have nearly identical muzzle velocities. The .50 has a better shaped bullet, the 20mm has more weight per unit of frontal area for better sectional density. Ballistic coefficient does favor the .50 but doesn't really come into play in an realistic air to air scenario (600 yds or under).

The M8 API was introduced in early 44. It was basically a copy of the Russian 12.7mm API round so there was no technical reason it could not have been introduced sooner for "what ifs"
However part of it's value was the incendiary ignited on impact as it was in the nose. It would give a flash on impact indicating the shooter was on target (tracer use was much diminished at this time) however very little incendiary material made it inside the aircraft if it hit anything substantial on the way in (or hit at bad angle).

I would note the examining wrecks or looking at wreck photos needs some interpretation. You can wind up with quite a bit of paint knocked off surrounding a rather small hole. You also have bullets hitting at rather oblique angles making large dents/scraps but no penetration when fired at long ranges. If you have a round "marking" then the bullet hit at a good angle, the more oval or elongated the hole/scrape the worse the angle.


and for instance.
View attachment 595131
supposed to have been shot down Friday 16th August 1940. in Scotland

Edit, correction, crashed near Worthing in Sussex. No 19 Squadron was equipped with Spitfires with 20mm guns at this time but they were based at Duxford near Cambridge.

.303s? AA fire? The RAF had how many 20mm armed aircraft in August of 1940 in the North of England and Scotland South coast?

What made the bigger holes?

What I will say is the Mk7 .303 round is actually a hunting bullet designed by Holland and Holland, it was designed to tumble after impact. If you look at the fin as an example the larger holes could very easily have been made by a Mk7 that tumbled after penetrating from the opposite side, only trouble I have is the alloy should be folded outwards, as the for right horizontal stabiliser, those long gashes are identical to the the ones I got when shooting into the bonnet of an old car wreck we had on the farm, bullets can and do make interesting holes in objects.

 

[nuuumannn]

When the RAF needed some ECM aircraft they knew just where to go; they used B-24's and B-17's.

And Boulton Paul Defiants and Avro Lancasters, de Havilland Mosquitoes, Vickers Wellingtons, Handley Page Halifaxes...

 

[MIflyer]

The jammers of 100 Group that flew missions over hostile territory were almost all B-24's and B-17's

Reference: "Confound and Destroy 100 Group and the bomber Support Campaign"

 

[MIflyer]

When F4U's with four 20MM guns were deployed to Okinawa in 1945, they found the guns would jam at high altitudes. The reason given was that the high altitude tests had been skipped, presumably to rush them into combat.. On the other hand, I am not aware of common problems with the P-38 20MM, although the four 20MM nose installation in the A-20 was phased out early due to gun problems.

 

[P-39 Expert]

View attachment 595129

.Used in the F4U-5 postwar

This is a two stage engine, right? Dual sidewinder first stage and internal second stage.

 

[P-39 Expert]

It was less reliable than the British version (Licence built) to start with as the British had modified theirs due to test results. Americans started with looser tolerances in general and a chamber about 1mm longer (?). The longer chamber allowed the cartridge to move forward when hit by the firing pin, this lead to a light primer strike and misfires. The Americans finally did get it straightened out but it took far to long. The Hispano was also sensitive to mounting, after all, it was designed to be bolted to a roughly 1000lb engine. The P-38s seem to have done OK, in part due the gun being mounted in a rather heavy cradle. Many of the wing guns (or even belly pack guns) did not get this heavy cradle.

In the US there was quite a bit of finger pointing as the gun makers blamed the ammunition makers and the ammunition makers blamed the gun makers.

However, as with with any weapon that spanned 6-7 years (first Hispano 404 cannon for the US was shipped in Feb 1938, the Americans did NOT get the Hispano from the British)
one sentence does not cover the whole situation. Four Companies built a total of 134,638 guns during WW II. after gun number 56,410 the American guns were identical to the British guns for all practical purposes. Which does leave a lot of guns in storage or out in service establishing a bad reputation. The final tally was:

The Navy got....................................21,228 guns
the Army got....................................13,272 guns
The British got..................................44,474 guns
stored:
...........Servicable...............................19,092 guns
.........UNservicable...........................35,995 guns
Lost or worn out...................................692 guns. (US service?)

By far the largest producer was Oldsmobile but even they stopped production in Feb 1944.

This is because the Americans had developed their own lightened, faster firing version called the T-31 of which 32,326 were produced by modifying most of the 35,955 AN M-2 guns held in stock as unserviceable. This started in the summer of 1944.

Always wondered why the P-39 stayed with the 37mm cannon, standardization would have indicated use of the 20mm. P-39 only carried 60 rounds which wasn't enough, bigger ammunition tray needed for 120-150 rounds.

 

[michaelmaltby]

".... Always wondered why the P-39 stayed with the 37mm cannon,"
Made by Oldsmobile. IIRC. Buy American ?

 

[tomo pauk]

So if the .30's aren't good enough what shot down the 3,000 or so aircraft lost in the BoB, harsh language?.

3000 shot down in BoB by whom?

 

[MIflyer]

The Flying Cannon was a big sales point for the P-39. Recall that Bell's first foray into fighters was the YFM-1, which had two 37MM guns. Consider how big a bomber would have to be fly all the way from Europe or Asia and hit the US mainland. How long would you have to shoot at a B-29 with nothing but .50 and .30 cal before it took notice of the insolent fly that was attacking it? Even in WWI there were those that said the rifle caliber machine gun was too small. A model of the SPAD was fitted with a 37MM gun firing through the prop shaft, hand loaded by the pilot; the biggest drawback was that the fumes nearly asphyxiated him.

Being able to carry a 37MM was a major selling point for the P-39 and despite its limited success they put it in the P-63, put it in the P-38D, and had plans to install it in the A-26 and A-41.

None of this AAAAAAAAH stuff! A P-39 would be Deadeye Dick, one shot one kill, no matter how big the enemy bomber was. The Soviets kept up with the idea after the war and put a 37MM in the Mig-15.

Even Curtiss thought it was a good idea.

 

[P-39 Expert]

The Flying Cannon was a big sales point for the P-39. Recall that Bell's first foray into fighters was the YFM-1, which had two 37MM guns. Consider how big a bomber would have to be fly all the way from Europe or Asia and hit the US mainland. How long would you have to shoot at a B-29 with nothing but .50 and .30 cal before it took notice of the insolent fly that was attacking it? Even in WWI there were those that said the rifle caliber machine gun was too small. A model of the SPAD was fitted with a 37MM gun firing through the prop shaft, hand loaded by the pilot; the biggest drawback was that the fumes nearly asphyxiated him.

Being able to carry a 37MM was a major selling point for the P-39 and despite its limited success they put it in the P-63, put it in the P-38D, and had plans to install it in the A-26 and A-41.

None of this AAAAAAAAH stuff! A P-39 would be Deadeye Dick, one shot one kill, no matter how big the enemy bomber was. The Soviets kept up with the idea after the war and put a 37MM in the Mig-15.

Even Curtiss thought it was a good idea.


View attachment 595264




View attachment 595265

Agree. A 20mm with 120 rounds would have saved about 80lbs of weight and standardized the guns, but there's no arguing with the 37mm's power. The .30cal wing MGs were certainly not needed with a 37mm cannon and twin .50cal MGs all in the nose. The resultant lighter P-39 would have outclimbed the Zero in '42 erasing the only real disadvantage of climb/ceiling.

Trajectory was relatively flat out to 400 yards which was about the outer limit of accuracy with any airborne gun. It was estimated that 60-80% of pilots shot down in WWII were unaware of their assailants so the relatively slow rate of fire would have only mattered in a maneuvering fight. If you were aware of your opponent you could normally escape fighter vs fighter combat unless you had a severe performance disadvantage.

37mm was great for ground attack also. After the jamming problem was solved in mid -'42 it became a great weapon. Russians said it was more reliable than the 20mm.

 

[MIflyer]

Even if the guy does not know you are there, unless it is a zero deflection up the kazoo shot, judging angles will be a significant challenge. Even at only 300 mph, in one sec you move 440 ft, during which time you have managed to fire a mere two 37MM rounds, only four rounds in 880 ft. It will be all impossible to correct your fire against airborne targets. I suppose that if you charge up to a bomber formation and let fly with everything you've got you might hit something.

It's too bad we did not have fast firing 15MM cannon like the Germans did in the 109F, or that we never finished developing the .60 caliber machine gun.

I have read of but a few cases of a P-39 hitting anything with the 37MM. below is one:

 

[P-39 Expert]

Even if the guy does not know you are there, unless it is a zero deflection up the kazoo shot, judging angles will be a significant challenge. Even at only 300 mph, in one sec you move 440 ft, during which time you have managed to fire a mere two 37MM rounds, only four rounds in 880 ft. It will be all impossible to correct your fire against airborne targets. I suppose that if you charge up to a bomber formation and let fly with everything you've got you might hit something.

It's too bad we did not have fast firing 15MM cannon like the Germans did in the 109F, or that we never finished developing the .60 caliber machine gun.

I have read of but a few cases of a P-39 hitting anything with the 37MM. below is one:
View attachment 595272

 

[P-39 Expert]

Russians would disagree with you. They viewed it as an optimal air to air weapon. They deleted the wing guns so they must have liked it. Remember there were also twin .50cal MGs in the nose. Fired 140 rounds/minute, closer to 5 rounds in two seconds. 2.14 seconds exactly. How was it impossible to correct your fire? Each shell was a tracer so you certainly could correct your aim. Also your calculations assume your target is standing still instead of moving in roughly the same direction as you.

Was the ultimate bomber destroyer.

 

[PAT303]

3000 shot down in BoB by whom?

More aircraft were shot down with LMG's in the BoB than anything else, over 40% of 109's were E -1/2's armed with four LMG's and considering that the 20mm ammunition on the E-4's was good for only about 9 sec's they did a lot of work with only two LMG's.