P-40 vs. ME-109

DerAdlerIstGelandet said:

I get exactly what you are saying. I do however not agree with you. I think the .50 was just fine for taking on the German fighters. I think that maybe a better weapon could have been designed, but the .50 was already built and ready to use. For an army that is trying to win a war of attrittion and needs to build a large army quickly, it was the way to go. Why waste time with R&D, when you can use something you already have?

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Why didn't we just go to war with the P-40 for the rest of the war? Why develop anything better?

The American .50 cal used much more powerful ammunition than the German MG 131.

The American Ammunition had a muzzle energy of about 17,800 joules per round compared to about 9,600 joules per round for the German 13x64B ammunition. This requires a somewhat larger (the empty case is 35mm longer than the German) and heavier gun, although perhaps with not quite difference between the two guns.

The Russian 12.7mm was even more powerful but the gun's light weight was purchased, in part, because of a much lower gun "life". This is not Barrel life but the life of the receiver and reciprocating parts. You can argue over the wisdom of designing/building guns with an expected life of 10,000rounds or better for combat planes but it was a real difference in design and weight.

The American (and Russian) .50s had shorter times of flight, higher impact velocity/energy and flatter trajectory which made air to air gunnery much easier. So much so that the US spent large sums of money and time trying to develop even higher velocity cartridges and guns during the war as the T17 series.

High Explosive weighs less than lead. Seems like HE rounds would achieve both a higher MV and a higher lethality.

Clay_Allison said:

Why didn't we just go to war with the P-40 for the rest of the war? Why develop anything better?

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The planning (drawings, tooling, production allocations and such) for most American fighters,and bombers was either completed or in advanced stages at the time of Pearl Harbor.

For instance there were 773 P-47Bs and Cs on order in Sept. of 1940 even thought the first prototype didn't fly until May of 1941. The first Production P-47 came off the line Dec. 21 1941. What do you want to do?
Stop production of the P-47 and spend months retooling the the Republic factory to build P-40s because you are NOW at war?


Fighter aircraft are a combination of things. You need an airframe/engine combination that will give you at least adequate performance and you need sufficient armament to bring down the enemy aircraft once you are in firing position. The .50 provided adequate armament even if it wasn't superior.

Clay_Allison said:

High Explosive weighs less than lead. Seems like HE rounds would achieve both a higher MV and a higher lethality.

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HE also has a density much closer to wood than metal. Look at even a German Mine shell. What percentage of shell weight is HE? the fuse is going to weigh a certain amount unless you get into some rather bizarre and questionable safety issues. With the stress of high velocity firing the shell walls have to be stronger (thicker) to stand the strain leading to less volume for the HE. With a near constant wall thickness the larger diameter shell will always show a much higher percentage of volume for HE content than a smaller diameter shell.

Light shells for caliber also act like Ping-Pong balls. High intital velocity but slow down really quick.

Shortround6 said:

HE also has a density much closer to wood than metal. Look at even a German Mine shell. What percentage of shell weight is HE? the fuse is going to weigh a certain amount unless you get into some rather bizarre and questionable safety issues. With the stress of high velocity firing the shell walls have to be stronger (thicker) to stand the strain leading to less volume for the HE. With a near constant wall thickness the larger diameter shell will always show a much higher percentage of volume for HE content than a smaller diameter shell.

Light shells for caliber also act like Ping-Pong balls. High intital velocity but slow down really quick.

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That's reasonable, yet there must be some reason why every other 12-13mm gun had them.

Clay_Allison said:

Why didn't we just go to war with the P-40 for the rest of the war? Why develop anything better?

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That is beyond the point. Now you are just nit picking. The point is the .50 was just fine for the job.

Shortround6 said:

Fighter aircraft are a combination of things. You need an airframe/engine combination that will give you at least adequate performance and you need sufficient armament to bring down the enemy aircraft once you are in firing position. The .50 provided adequate armament even if it wasn't superior.

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Thank you...

I wouldn't be complaining so much if early war American planes weren't so overweight. It wouldn't have killed them to stress the plane to 10 Gs rather than 12, lighten the armament, supercharge the engine a little better, and make them fly like fighters instead of ground pounders. A little attention to a lot of small details could have saved lives.

Clay_Allison said:

That's reasonable, yet there must be some reason why every other 12-13mm gun had them.

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Did the Russian 12.7 have HE rounds?

The Italian and Japanese did but their rounds were only a bit more powerful than the German round. And as a bit of comparison they carried explosive charges of about 1-2 grams. 20mm HE shells carried 6-10 grams with the German Mine shells roughly doubling that (20 grams).

American .50 API rounds carried about as much incendiary material as the Axis 12.7-13mm projectiles carried HE.

Clay_Allison said:

I wouldn't be complaining so much if early war American planes weren't so overweight. It wouldn't have killed them to stress the plane to 10 Gs rather than 12, lighten the armament, supercharge the engine a little better, and make them fly like fighters instead of ground pounders. A little attention to a lot of small details could have saved lives.

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Or traded lives.

A plane stressed to 10 Gs might not be able to take as much punishment as the one stressed to 12 Gs. So fewer pilots are saved by their "sturdier" aircraft. Granted fewer of them might have been shot up as bad if they had more speed and maneuverability to begin with but that plan didn't wind up working so well for the Japanese did it?

Lighter armament? Few kills or cripples for the same number of firing opportunities? More enemy pilots and planes escaping to fight another day? Or does the added speed an maneuverability translate into more firing opportunities to compensate? enough more?

edit: American planes were also over weight because they housed more internal fuel than most of their contemporaries. Shorter range/endurance in the Pacific might not do much for firing opportunities or for pilot survival on over water flights.
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Lighter armament? Few kills or cripples for the same number of firing opportunities? More enemy pilots and planes escaping to fight another day?

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I mean armament that weighs less, like 4 light cannon over 6 heavy machine guns. We discussed in another thread how the Japanese 20mm Ho-5 cannon was based on the Browning MG and carried a lot more punch at slightly lower unit weight than the M2. The 50 BMG necked up to 20mm could have been roughly equivalent to having MG 151/20s.

4 light 20mm cannons would be lighter armament, but more powerful.

I never saw combat but fired an M2 on the range at Fort Hood and believe me it is an effective weapon. That round will tear an old deuce and one half to pieces and I can only imagine what it would do to a WW2 aircraft, especially a fighter. The fact is that four gun P51B and Cs and four gun Wildcats were very effective in both theatres. Four gun Martlets served with the FAA and were effective aginst JU88s and FW200s and Eric Brown called the armamament of the Wildcat "very powerful."

Clay, i think a lot of what you're missing is the context of the weapons you're describing.

The US was developing alternatives to the 50 caliber. The 14.7mm caliber was a late war development that never saw fruition. 20mm was also being worked on. 50 caliber did its job.

As i said before the 20mm was not seen as an effective or reliable in the eyes of the US for air to air combat. This had a lot to do with MV and firing time but also a majoirty of the these cannons suffered problems at altitude. There was a report that well documented both these findings on this forum. It did not mean there was not a need or a demand for a higher caliber, just simply put, the 1941 hispano was not fit for US operations. The British made use of it, however, they were also defending home land from invading bombers. I read that many of these cannons still had problems and Spitfire pilots still felt more confident flying with 303s.

The US also refused to use HE rounds with their browning because the trade off in range was not worth the result. You need a denser heavier round to maintain better velocity. The 50 caliber was preferred in part not only because of its range but at high speeds the projectiles maintained much of their velocity. 20mm cannons took most of the war to match the velocity capable of the 50s and still were not fit for high altitude missions.

I hate seeing comparisons to cannon weilding planes because in the context of the war, Germans were using cannons on heavy bombers, Japanese cannons were considered low velocity weapons and only useful at short range. A Yak has 9-12 seconds of trigger time, compared to P-47D 30 seconds. Which plane could hover over roadways for half the day shooting at anything that tries to drive on them?

Point is each weapon has a roll, and making blanket statements about gun weight and ammo has little to do with their use.


Bill

Clay_Allison said:

I mean armament that weighs less, like 4 light cannon over 6 heavy machine guns. We discussed in another thread how the Japanese 20mm Ho-5 cannon was based on the Browning MG and carried a lot more punch at slightly lower unit weight than the M2. The 50 BMG necked up to 20mm could have been roughly equivalent to having MG 151/20s.

4 light 20mm cannons would be lighter armament, but more powerful.

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Lower unit weight? I think the Japanese cannon weighed 6-8kg more than American .50cal aircraft gun.

The total weight would be lower than six .50s including ammo but I think the weight savings is not as much as you might think. the Japanese 20mm ammo is around twice as heavy per round as .50 cal ammo. an even swap for weight (not including links) gives 221 rounds of 20mm HE ammo per gun (AP was somewhat heavier) for the four Japanese cannon. Not bad but not much of weight loss either. Trading ammo for weight loss means less firing time.

It is also about 4.7mm bigger in diameter of the case body compared to a .50cal which means the Japanese round as around 50% more case capacity per unit of length. A necked up .50 cal would have considerably less performance than the Japanese cartridge.

Hi, billwager, some questions disagreements:

As i said before the 20mm was not seen as an effective or reliable in the eyes of the US for air to air combat.

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When the USAAC/USN established that?

20mm cannons took most of the war to match the velocity capable of the 50s and still were not fit for high altitude missions.

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1. Hispano shells were any bit as fast as .50
2. Is the speed of .50 better asset then destructive power of medium-velocity 15-20mm cannon shell?
3. Is it only the US Hispano-derivarive susceptible to the adwerse effects of high altitude, or the othe cannons suffered from it?

Germans were using cannons on heavy bombers,

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Poland, Norway, Low countries, France, Battle of Britain, Mediterrranean, the whole Russian front were void of heavy bombers, yet Luftwaffe used cannons there too

A Yak has 9-12 seconds of trigger time, compared to P-47D 30 seconds. Which plane could hover over roadways for half the day shooting at anything that tries to drive on them?

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If the P-47D had 4 cannons instead of 8 HMGs, the firing time would remain the same, end fire power would be upped.

Point is each weapon has a roll, and making blanket statements about gun weight and ammo has little to do with their use.

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Cannons were used for same role as MGs in fighter planes of WW2 - to kill the enemy plane. Cannons were better for the job.

The ideal kind of gun IMO largely depends on what you are shooting at.

a)unprotected A/C: rifle caliber machine guns will do just fine
b)protected single and twin engine A/C: heavy machine guns
c)four engine heavy bombers: cannons

Since the USAAF did not have to worry about c) the admittedly more powerful 20mm cannon was not necessary.


With regard to the (over)weight of pre-war designs like the P-40 and F4F I wonder why the US mostly kept the six gun armament. At 70lb per gun, 0.3lb per round and IIRC 450 rds/gun a Wildcat could have lost 410lb and retained more than enough firepower as the performance of the four-gun Wildcats before Midway shows.

The P51 with four cannon had a firing time of 12.5 seconds, the P51B had a firing time of 21 seconds. The P47, with a full load of ammo had a firing time of aound 28 seconds. The F6F when equipped with two 20 mms had a firing time of 22.5 seconds and that was with 225 rounds per gun. Why do you think the P47 could carry enough 20 mm cannon rounds to equal the 28 seconds firing time? 20 mm ammo weighs more and takes up more space than 50 BMG ammo. Belted 20 mm ammo could weigh as much as .766 pound per round whereas the max weight of 50 BMG was .311 pound per round. With 8 MGs the P47 is more than twice as likely to hit the target as with four cannon and that does not even take into account the longer firing time. On top of that, railroad locomotives are probably more likely to be put out of service by 50 cal rounds than by 20 mm rounds and trucks don't need to be hit by 20 mms as 50 BMGs will do the job just as well, just like with fighters. Another issue with explosive cannon shells is that a certain percentage of them will be duds and not do as much damage as the solid round of the 50 cal.

premise i'm agree that .50 it's enough for shoot down enemy SE fighters, imho also less powered HMG are enough but
little comparation
2 Hispanos (600 rounds), late model, versus 8 .50 Browning (2400 rounds)
they have comparable MV and ROF (the hispanos are a bit low in both)
a hispano weight around 30% more that a .50 so over 150 kg less for the hispanos
the hispano ammo weight it's around 3 time of .50 ammo (for true less) so over 80 kg less for hispanos
time of fire it's for both ~25"
you've in air around 4 time .50 round that 20mm but the 20mm power it's over 4 time of that .50 (i can tell 4 and 1/4 or also 4 and 3/4) so the 20mm hitting only 1/4 of time of .50 but give almost 10% more damage in total, and you've a plane 230 kg lightest.

tomo pauk said:

Hi, billwager, some questions disagreements:

When the USAAC/USN established that?

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I'm not sure exactly when, this was early in the war when Hispanos and 50s were weighed against each other.
I'd site sources but this is knowledge gained through collective reading.

1. Hispano shells were any bit as fast as .50,

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This is debatable but what i think most people don't realize is that muzzle velocity is measured in the first few feet of fire.
Cannon rounds slow down faster at high speeds, or at least thats what was found early on.

2. Is the speed of .50 better asset then destructive power of medium-velocity 15-20mm cannon shell?

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If it takes 10 50 calibers rounds to do the same job as 4 20mm shells then no, however speed and rate of fire gives you better odds that your 50 calibers are going to land. I'm not implying 10 rounds of 50s are equal to 4 20mm shells, rather each combination is capable of destroying a plane.

It was also determined that cannons (not sure of the caliber) had an effective range of 250y, where 50 caliber had an effecitve range of 850y. That's in level flight. In turns it was suggested the range of the 50 is reduced to 250yards.
I can only question where that leaves cannons.

The Luftwaffe detirmined it takes an average of 20 20mm shots to down a B-17. They also figured that at a 2% hit rate means they would need to fire 1000 rounds. So the other option was to increase firing time. The way to do that is to add more guns. Thats why some vairiants of the 190 include 4 wing cannons and two in the cowling.

We see lighter configurations on German fighters intended for air to air combat or dogfighting, MGs are typically part of that arrangement although cannons were also used for shots at closer range.

3. Is it only the US Hispano-derivarive susceptible to the adwerse effects of high altitude, or the othe cannons suffered from it?

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There is no real difference, IMO. They were the same gun just manufactured in different places and expected to fit and work in different airplanes. I think the British used it because they needed it, but the US didn't because it wasn't up to their standards.
The altitude problem was more an issue of gun heating, (late war) because as far as i know, the Tempest mk V was able to make use of them, but then again the Tempest stayed under 26k ft for the most part.

There is a report that out lines more of this discussion if you search for it on this forum.

Poland, Norway, Low countries, France, Battle of Britain, Mediterrranean, the whole Russian front were void of heavy bombers, yet Luftwaffe used cannons there too

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Good point.
I guess I'm reffering to heavier installations, but it is worth noting that the 109 and 190 both used MGs to the end of the war.
More of a point to how a gun and its ammo is designed for the roll. You don't use 50 calibers to shoot down heavy bombers you use cannons.

Some of this depends on ammunition. The 20mm Hispano guns are more effective than the the .50 and in later years fired a combination API round that equaled the penetration of the .50 API round but carried 10 times the incendiary material.

Mission--- bomber intercept vrs bomber escort. A shorter firing time can be accepted because the interceptor will be over home base and can land to rearm an engage bombers on the way out or intercept a later attack. Bombers are usually bigger and tougher. For bomber escorts running out of ammo on the outward leg is a problem. There targets are usually single engine fighters or at worst twin engine fighters. Their goal is a little different to. Goal of a bomber interceptor is to destroy the bomber or at least get it to turn back before dropping bombs. Goal of a bomber escort is to keep enemy interceptors for doing the same to the bombers they are protecting. Shooting down the enemy is nice and keeps them from flying another day but merely damaging and interceptor and driving it away doesn't have quite the same consequences as damaging a bomber that still makes it to the target area.

The US should have been able to do better in regards to aircraft armament but to claim they weren't trying or at least thinking about it doesn't go with the facts.
Pre-war they had investigated a 23X139mm cartridge and four different guns to fire it. They had also tested the 23mm Madsen cannon and a French 25mm gun. Then we have the 37mm gun fitted to Aircobras, Aircudas and in one instance the top turret of the XB-19. It was also specified in a number of experimental aircraft like the XP-67 and the XP-54.

Good aircraft guns aren't quite as simple a device as some would like to think. It usually took a number of years from prototype to squadron use. There are reports of a German MG 151 in Spain in 1938 yet it took another 3-4 years to get it into squadron service with the only alternative the not so satisfactory MG/FF.