Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (1 Viewer)

[GrauGeist]

The PT boat guys sure liked it when the AAF guys got rid of the Oldsmobile 37mm, they used that on their boats and it was such a hit, later PT boats were manufactured with the 37mm as standard equipment.

 

[Stig1207]

The P-40D had four .50 cal guns and RAF Ace Caldwell, I believe it was, preferred it that way. There was a case where he was covering a convoy and two 109's came down out of the Sun and hit him good. He turned around, shot down one of the 109's and sent the other one packing.

The story goes that it was Werner Schoer that shot up his plane and wounded Caldwell, but he turned around and shot down Schoer's wingman and sent Schoer packing. However, the only part that has any basis in fact is the bit where Schoer shot up Caldwell 's P-40 and wounding him.

There is a Hollywood movie gone begging in Clive Caldwell's exploits.

 

[P-39 Expert]

The P-40D had four .50 cal guns and RAF Ace Caldwell, I believe it was, preferred it that way. There was a case where he was covering a convoy and two 109's came down out of the Sun and hit him good. He turned around, shot down one of the 109's and sent the other one packing.

Deleting the four .30 cal would have decreased the value of the P-39 for strafing, and on the 'Canal it w as sorely needed for that. The Marines credited the P-400's of the 67th with saving Henderson Field with their close support. And I think deleting the 37MM and putting in a third .50 cal would have been a good idea for optimized air to air P-39's. With the "roman candle" firing rate of the cannon, the chance of hitting anything with the 37MM other than a bomber going straight and level was pretty slim and its trajectory was so different from that of the .50 cal and .30 cal that hitting something other than the ground with all three was unlikely.

Strafing ground troops was about all the .30cal MG was good for, it certainly wasn't effective against other planes. It wasn't good enough for any other contemporary US fighter.

The 37mm cannon had a flat trajectory out to about 400 yards which was about the outer edge of accuracy for any guns air to air. Soviets liked it.

Substituting a .50cal MG for the 37mm wouldn't have provided enough firepower and it would have screwed up the balance. Better to substitute a 20mm cannon with a bigger ammunition tray.

 

[GrauGeist]

Sorry to disagree, but a .30 (or .303) will easily pass through aluminum, penetrate fuel tanks, sever flight controls and so on.

Saburo Sakai was nearly killed by a .30 caliber bullet from an SBD that penetrated his cockpit, so be careful about discounting it.

 

[P-39 Expert]

Sorry to disagree, but a .30 (or .303) will easily pass through aluminum, penetrate fuel tanks, sever flight controls and so on.

Saburo Sakai was nearly killed by a .30 caliber bullet from an SBD that penetrated his cockpit, so be careful about discounting it.

I enjoy the debate. .30s were worthless against armored German planes. May have been of limited use against unarmored Japanese planes. If four .50s was adequate, then a 37mm and twin .50s were certainly adequate. Lose the .30s and outclimb the contemporary Zero. Big advantage.

 

[Shortround6]

Hmmmm, American .30 cal was worthless.

Japanese 7.7mm in Ki 27s, Ki 43s and cowl guns in A6M shot down how many american planes?
British ,303s (actually same round as the Japanese 7.7) shot down how many German aircraft in 1939-41?

American .30 cal has 13% more kinetic energy than Japanese 7.7mm.
British kept four .303 guns in the Spitfire until 1944?in part because the 20mm ran out of ammo before the .303s.

The 37mm was notorious for jamming in the early versions. with a 30 round ammo supply it was good for about 12 seconds of firing time.

if the 37 jams or is out of ammo the P-39 had the fire power of a P-40C if it kept the .30 cal guns. Without them?????

 

[MIflyer]

An article I found said that the underwing .50 cal guns on the later P-39's really screwed up the handling and caused it to be actually slower than the earlier models. We have some evidence that some Soviet P-39's had the underwing .50 cal guns removed.

 

[MIflyer]

British kept four .303 guns in the Spitfire until 1944?in part because the 20mm ran out of ammo before the .303s.

Good Point! And the RAF pressed hard to get .50 cal guns installed to replace the .303 in Spitfires in time for the Normandy invasion because so many Spits would be required for fighter bomber duties.

 

[P-39 Expert]

Hmmmm, American .30 cal was worthless.

Japanese 7.7mm in Ki 27s, Ki 43s and cowl guns in A6M shot down how many american planes?
British ,303s (actually same round as the Japanese 7.7) shot down how many German aircraft in 1939-41?

American .30 cal has 13% more kinetic energy than Japanese 7.7mm.
British kept four .303 guns in the Spitfire until 1944?in part because the 20mm ran out of ammo before the .303s.

The 37mm was notorious for jamming in the early versions. with a 30 round ammo supply it was good for about 12 seconds of firing time.

if the 37 jams or is out of ammo the P-39 had the fire power of a P-40C if it kept the .30 cal guns. Without them?????

37mm jamming was fixed in early/mid '42 with the K model (Bell model 26) which provided the small exit vents in the nose to exhaust heated cockpit air ducted into the gun bay. This prevented the gun from freezing at altitude. Soviets considered the 37mm very reliable and more reliable than the 20mm.

If the Japanese twin .30s shot down so many American planes then the twin .50s in the P-39 made short work of unarmored Zeros.

The British moved forward with the 20mm cannon because the .30s weren't powerful enough, even though there were eight of them. Spitfires with 20mm cannons held 120 rounds, about 12 seconds firing time. P-38s with one 20mm cannon had 150 rounds which was only about 15 seconds firing time.

Whole purpose of losing the .30s (and nose armor) was to improve climb and combat ceiling (1000fpm). If Zeros could get above you then your 40mph speed advantage was worthless. If you could get above them then you had every advantage except turn.

 

[GrauGeist]

30s were worthless against armored German planes.

But the Germans used a fixed 7.92mm MG (MG17) for their aircraft's armament during the early part of the war: Bf109, Fw190, He112, Bf110, Ju87, etc.

The MG17 was literally a .31 caliber MG, so how were the Germans able to overcome the British armor, then?

 

[P-39 Expert]

An article I found said that the underwing .50 cal guns on the later P-39's really screwed up the handling and caused it to be actually slower than the earlier models. We have some evidence that some Soviet P-39's had the underwing .50 cal guns removed.

View attachment 594907

Just a couple of errors in this article, all in the last paragraph. No -35 engines in any Q models. All N/Q models had the -85 engine with 1200hp for takeoff and 1125hp at 15500'.

The 1150hp -35 was used in the P-39C/D/D-1/F models. The -63 with 1325hp (takeoff) was used in the D-2/K/L models. The -83 was used in the M and differed from the -85 only in reduction gear ratio. Power section was the same.

If that $22854 unit price in the last contract was correct then the Q was quite a bargain.

 

[P-39 Expert]

But the Germans used a fixed 7.92mm MG (MG17) for their aircraft's armament during the early part of the war: Bf109, Fw190, He112, Bf110, Ju87, etc.

The MG17 was literally a .31 caliber MG, so how were the Germans able to overcome the British armor, then?

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.

 

[GrauGeist]

WWI aircraft weapons were in the .30 caliber range (.30 to .32) as were the majority of fighter's armament in the interwar years. It wasn't until the late 1930's that the U.S. started adopting the .50 - and even then, it was a combination of one .30 MG and one .50 MG. The SBD was one of the first production U.S. aircraft that was equipped with two fixed foreward .50 MGs.

The escalation of heavy calibers follows the natural progression of warfare: over-power the enemy.

Otherwise, fighters would not have been equipped with higher output engines and better protection, tanks would not have been up-gunned and up-armored, Battleships and Cruisers would not have had larger guns and faster speeds and infantry would still have been armed with bolt-action rifles.

The idea of having more MGs or heavier caliber MGs and/or cannon was to insure downing the enemy regardless of the enemy's protection. The Luftwaffe wasn't arming their Sturmbocks with cannon because they thought the B-17 was so well armored (because it wasn't), they did it because they wanted to bring the B-17 down as quick as possible.

As mentioned before, the .30 (or .31, etc.) will penetrate aluminum skin, stringers, spars, control lines, fuel tanks, supply lines, engine components, glass/perspex, and so on - which is the VAST majority of an aircraft presented. Pilot and engine armor is just a small portion and it will not prevent an aircraft for being damaged beyond function.

 

[MIflyer]

I have read that for the Hawk 81A's the RAF used in North Africa they removed the two .50 cal nose guns and replaced them with .303 guns. The reason was logistics; the .303 round was standard for British forces in the air, on the ground and at sea.

I also read where during the BoB they took a section of Spitfire armor plate and fired a .303 round into it to demonstrate to the pilots that they had some protection. . The round went through the armor like it was balsa wood.

By the way, I would assume the price for a P-39Q did not include the V-1710 engine, radios and guns, all of which would have been GFP.

 

[tomo pauk]

By the way, I would assume the price for a P-39Q did not include the V-1710 engine, radios and guns, all of which would have been GFP.

Yes, the price of complete aircraft was around 50000 $ (similar with P-51; the P-40 dropped to ~45000 by 1944).

 

[GrauGeist]

I also read where during the BoB they took a section of Spitfire armor plate and fired a .303 round into it to demonstrate to the pilots that they had some protection. . The round went through the armor like it was balsa wood.

Several years ago, my friends and I were at the range and they were plinking at a 5/16" thick steel target with their .223s set up aboit 35 yards out.
It would ring like a bell with their hits. Being a smartass, I got out my 7x57 Mauser and took a shot. The target didn't move - ok, so I missed, no problem, took more careful aim and let fly. Again, nothing - I missed again??
Baffled, I went out and looked at the target. Scores of divots from the .223 impacts and lo and behold: two large holes near the center. The 7x57 passed through it like it was cardboard...

.30 caliber rounds can and will do damage.

 

[tomo pauk]

If anyone is interested - the 'flyaway' cost of some USAAF A/C:

 

[P-39 Expert]

Several years ago, my friends and I were at the range and they were plinking at a 5/16" thick steel target with their .223s set up aboit 35 yards out.
It would ring like a bell with their hits. Being a smartass, I got out my 7x57 Mauser and took a shot. The target didn't move - ok, so I missed, no problem, took more careful aim and let fly. Again, nothing - I missed again??
Baffled, I went out and looked at the target. Scores of divots from the .223 impacts and lo and behold: two large holes near the center. The 7x57 passed through it like it was cardboard...

.30 caliber rounds can and will do damage.

And there are accounts from British pilots in the BoB of emptying their entire magazines of eight .30cal guns into a single He111 and watching it fly on to the target. Now I much prefer actual documented tests to anecdotal stories but if the .30cal gun was sufficient then the .50cal, 20mm, 30mm, 37mm guns would not have been developed. And the .30cal MG would have been used on AAf fighters, which it was not, except for the P-39.

 

[Acheron]

Several years ago, my friends and I were at the range and they were plinking at a 5/16" thick steel target with their .223s set up aboit 35 yards out.
It would ring like a bell with their hits. Being a smartass, I got out my 7x57 Mauser and took a shot. The target didn't move - ok, so I missed, no problem, took more careful aim and let fly. Again, nothing - I missed again??
Baffled, I went out and looked at the target. Scores of divots from the .223 impacts and lo and behold: two large holes near the center. The 7x57 passed through it like it was cardboard...

.30 caliber rounds can and will do damage.

Careful! I am an amateur, but I am stumbling over the 35 yards (32 meters). From the stories about the RAF gun convergence debate, typical engagement ranges seemed to be around 750 feet (~225 meters). Doesn't that make a considerable difference in how much energy the bullet will retain?

 

[MIflyer]

Yes, in both the Spitfire armor "test" and the gun range test they were firing from a lot closer than actual combat, where 200 yards would have been considered to be "close."