Why no heavier RAF machine gun calibres?

MiTasol said:

Just that the the P-51 was the most important allied fighter in WW2.

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I would not agree.

It's a common debate among aviation enthusiasts and historians! The P-51 Mustang is often lauded for its significant impact, especially with its long-range escort capabilities, which allowed Allied bombers to reach deep into enemy territory. However, declaring it as the "most important" is subjective, and there are arguments to be made for other aircraft as well.

For instance:
Supermarine Spitfire: Essential in the Battle of Britain and a symbol of resistance.

Hawker Hurricane: Also played a crucial role in the Battle of Britain, shooting down more enemy aircraft than the Spitfire.

P-47 Thunderbolt: Known for its ruggedness and ground-attack capabilities.

F4U Corsair: Highly effective in the Pacific Theater, particularly in carrier operations.

Each of these aircraft contributed uniquely to the Allied efforts. The P-51's achievements can't be understated, but the overall success was a result of many planes and pilots working together.

Lockheed P-38 Lightning was another highly influential fighter during World War II. It was notable for its distinctive twin-boom design and versatility. Here are a few highlights:

Versatility: The P-38 was used in various roles including fighter, bomber escort, reconnaissance, and ground-attack missions.

Long Range: With its twin engines, it had the range to conduct long-distance missions, which was especially valuable in the Pacific Theater.

High Performance: It was one of the fastest aircraft in the Allied arsenal and had a significant impact in both the European and Pacific theaters.

Just like the P-51 Mustang, the P-38 Lightning was a crucial part of the Allied air strategy and made significant contributions to the war effort.

The Grumman F4F Wildcat and F6F Hellcat were both significant fighters in the Pacific Theater during WWII, each contributing greatly to the Allied victory.

F4F Wildcat
Early War Workhorse: The F4F Wildcat was the primary naval fighter for the U.S. Navy and Marine Corps in the early years of WWII.

Tough and Reliable: Known for its ruggedness, the Wildcat could take a lot of damage and still return to its carrier.

Key Battles: Played a crucial role in battles such as Midway and Guadalcanal.

F6F Hellcat
Successor to the Wildcat: Designed to outperform the Japanese Zero, the Hellcat quickly became the U.S. Navy's dominant carrier-based fighter.

Impressive Combat Record: The Hellcat achieved an incredible kill-to-loss ratio, contributing to the air superiority in the Pacific.

Production Numbers: Over 12,000 Hellcats were produced, making it one of the most produced fighters of WWII.

Both aircraft were critical in turning the tide of the war in the Pacific, showcasing the innovation and resilience of the Allied air forces.

Hawker Hurricane, Curtiss P-40, and the Grumman Wildcat (which does look good in blue paint). Most under appreciated.
That list is extensive. Let's add the Swordfish, Beaufighter, PBY.......

I think that the FM-2 Wildcat, produced by Eastern Aircraft, had such increased performance that it was about as good as the Hellcat in fighting the vast majority of Japanese aircraft, with the exception of higher altitudes. But the Hellcat was much easier to fly than any model of the Wildcat and also was a true fighter bomber, so much so that the practice of sending torpedo or dive bombers with a fighter escort to scout around the fleet was replaced with just Hellcats. I suppose that the ARC-5 radio installation used in the later Hellcats, which featured an HF comm channel as well as 5 VHF channels helped in its scouting role. It also become common for Hellcats to be equipped with bombs when sent with a strike force.

But I think that as far as a "Best Fighter" it is hard to think of a situation in the first half of the war where we would have not been better off with Merlin Mustangs than what we actually had. From the BoB to hasty scrambles on 7 Dec 41, to the Western Desert, to the AVG, to Guadalcanal, to Italy, to the CBI, to Normandy, to the PI, Merlin Mustangs would have been better than the alternatives. Admittedly it was not as survivable at ground attack as the P-47 and Typhoon, but it weren't no slouch, either, and was leagues ahead of the Spitfire for that mission.

MIflyer said:

I think that the FM-2 Wildcat, produced by Eastern Aircraft, had such increased performance that it was about as good as the Hellcat in fighting the vast majority of Japanese aircraft, with the exception of higher altitudes. But the Hellcat was much easier to fly than any model of the Wildcat and also was a true fighter bomber, so much so that the practice of sending torpedo or dive bombers with a fighter escort to scout around the fleet was replaced with just Hellcats. I suppose that the ARC-5 radio installation used in the later Hellcats, which featured an HF comm channel as well as 5 VHF channels helped in its scouting role. It also become common for Hellcats to be equipped with bombs when sent with a strike force.

But I think that as far as a "Best Fighter" it is hard to think of a situation in the first half of the war where we would have not been better off with Merlin Mustangs than what we actually had. From the BoB to hasty scrambles on 7 Dec 41, to the Western Desert, to the AVG, to Guadalcanal, to Italy, to the CBI, to Normandy, to the PI, Merlin Mustangs would have been better than the alternatives. Admittedly it was not as survivable at ground attack as the P-47 and Typhoon, but it weren't no slouch, either, and was leagues ahead of the Spitfire for that mission.

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If we're going to pick a fighter that doesn't exist in 1940 to win the Battle of Britain I pick the Gloster Meteor.

MIflyer said:

I think that the FM-2 Wildcat, produced by Eastern Aircraft, had such increased performance that it was about as good as the Hellcat in fighting the vast majority of Japanese aircraft, with the exception of higher altitudes. But the Hellcat was much easier to fly than any model of the Wildcat and also was a true fighter bomber, so much so that the practice of sending torpedo or dive bombers with a fighter escort to scout around the fleet was replaced with just Hellcats. I suppose that the ARC-5 radio installation used in the later Hellcats, which featured an HF comm channel as well as 5 VHF channels helped in its scouting role. It also become common for Hellcats to be equipped with bombs when sent with a strike force.

But I think that as far as a "Best Fighter" it is hard to think of a situation in the first half of the war where we would have not been better off with Merlin Mustangs than what we actually had. From the BoB to hasty scrambles on 7 Dec 41, to the Western Desert, to the AVG, to Guadalcanal, to Italy, to the CBI, to Normandy, to the PI, Merlin Mustangs would have been better than the alternatives. Admittedly it was not as survivable at ground attack as the P-47 and Typhoon, but it weren't no slouch, either, and was leagues ahead of the Spitfire for that mission.

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If you had a Merlin Mustang in production and being delivered from USA in 1940 I doubt that it would have the high speed low drag aerofoils that made it so fast, it would also have a 1940 Merlin and 1940 fuels and had a dry weight of around 1 ton more than a Spitfire, so although it would have been good to have perhaps not the game changer that a 1944 P-51D would be, but the P-51D came into service after the Me 262 so its superiority was in numbers, not performance.

MIflyer said:

But I think that as far as a "Best Fighter" it is hard to think of a situation in the first half of the war where we would have not been better off with Merlin Mustangs than what we actually had. From the BoB to hasty scrambles on 7 Dec 41, to the Western Desert, to the AVG, to Guadalcanal, to Italy, to the CBI, to Normandy, to the PI, Merlin Mustangs would have been better than the alternatives. Admittedly it was not as survivable at ground attack as the P-47 and Typhoon, but it weren't no slouch, either, and was leagues ahead of the Spitfire for that mission.

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We could say the same thing about the P-80.

It is hard to think of a situation in the first half of the war where we would have not been better off with P-80s than what we actually had.

pbehn said:

If you had a Merlin Mustang in production and being delivered from USA in 1940 I doubt that it would have the high speed low drag aerofoils that made it so fast, it would also have a 1940 Merlin and 1940 fuels and had a dry weight of around 1 ton more than a Spitfire, so although it would have been good to have perhaps not the game changer that a 1944 P-51D would be, but the P-51D came into service after the Me 262 so its superiority was in numbers, not performance.

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There was the P-38L and the P-47N late in the war. Either could compete with the P-51.

re

Alan Stevens said:

There was the P-38L and the P-47N late in the war. Either could compete with the P-51.

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IIRC the Fighter Conference said otherwise. While all 3 had good range, the P-38L and P-47N took about 2x the fuel that the P-51 used. The only advantage the P-38L had over the Merlin P-51 was climb. The only advantage the P-47 had was performance at very high altitude (over 30,000 ft?).

When the P-38, P-47, and P-51 were tested in mock air combat against the P-80A it was found that the P-51 was the only airframe that had a chance - although said chance was slim. I do not remember if the P-80 tests vs the other 3 airframes were part of the Fight Conference tests or separate.

ThomasP said:

IIRC the Fighter Conference said otherwise. While all 3 had good range, the P-38L and P-47N took about 2x the fuel that the P-51 used. The only advantage the P-38L had over the Merlin P-51 was climb. The only advantage the P-47 had was performance at very high altitude (over 30,000 ft?).

When the P-38, P-47, and P-51 were tested in mock air combat against the P-80A it was found that the P-51 was the only airframe that had a chance - although said chance was slim. I do not remember if the P-80 tests vs the other 3 airframes was part of the Fight Conference tests or separate.

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Fuel consumption wasn't much if any issue when trying to win a world war, at least with those aircraft, and the U.S. had the refinery capacity to make it moot.

The above was the USAAF analysis, not mine.

ThomasP said:

The above was the USAAF analysis, not mine.

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My comment about the fuel consumption did not question the figure you posted.

Understood, but the USAF and USN considered the difference in fuel usage important.

Alan Stevens said:

There was the P-38L and the P-47N late in the war. Either could compete with the P-51.

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Both using twice the fuel and providing a far larger target for the Germans to see and shoot at.

Alan Stevens said:

Fuel consumption wasn't much if any issue when trying to win a world war, at least with those aircraft, and the U.S. had the refinery capacity to make it moot.

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• Lower fuel consumption allows a plane to fly further, which seems to have been an important consideration for escort fighters of the era.
• You still have to get the fuel to the air bases in England. Saying fuel consumption doesn't matter seems disrespectful to the thousands of men who died bringing supplies, including fuel, over the Atlantic. Though by the time the Mustang starts showing up in numbers the Battle of the Atlantic is practically over, but still.

MIflyer said:

leagues ahead of the Spitfire for that mission.

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Where would your 9150 lb Mustang be leagues ahead of a 6172 lb Spitfire IIa in 1940 when they would both be fitted with the Merlin XII and 100 octane fuel?.

About the same leagues as the later Spitfires that were entering service when the various Mustang models entered service using the same engines.

I am sure someone here can put together a quick table of each model using essentially the same engine and comparing range, speeds at cruise altitude and disposable payload. It should prove most enlightening.

Alan Stevens said:

There was the P-38L and the P-47N late in the war. Either could compete with the P-51.

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The whole strategy was a preparation for D-Day. Longer range p-47s didnt appear until around D-Day and the P-47N hardly appeared at all during the war. The US had to go with what it had at the beginning of 1944 100 P-51s and 100 P-38s. Waiting for the P-47N would mean D-Day wasnt needed, the Russians would be in France.

PAT303 said:

Where would your 9150 lb Mustang be leagues ahead of a 6172 lb Spitfire IIa in 1940 when they would both be fitted with the Merlin XII and 100 octane fuel?.

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A 400 mph fighter in 1940, that weights 8100 lbs? Where do I sign?

PAT303 said:

WW2 started in October 1939, P51B's did their first missions with the 8th AF March 1944? correct me if I'm wrong so to say the war was ''not lost'' because of the contributions the Spit Hurri P40 and Wildcat provided for 4 years before the P51 flew the missions it's most noted for is derogatory at best.

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Lee Mallory cancelled the long range Spitfire project

MiTasol said:

About the same leagues as the later Spitfires that were entering service when the various Mustang models entered service using the same engines.

I am sure someone here can put together a quick table of each model using essentially the same engine and comparing range, speeds at cruise altitude and disposable payload. It should prove most enlightening.

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A comparison of late model fighters is here:
It doesn't indicate whether the Mustang III uses the V-1650-3 or the 1650-7. If it does have the -7, it is basically the same engine as the Merlin 66 used in the Spitfire LF IX. The -3 will show better performance at higher altitudes and worse performance at lower altitudes. Comparing the performance characteristics shown it is clear that the Spitfire is streets ahead of the Mustang in the most important metric for an interceptor, rate of climb. Even in 1944 the Spitfire IX is far superior in the interceptor role. Americans tend to discount the importance of the interceptor role because they didn't really do it much. They enjoyed the protection of far and away the best air defense system of WWII. Their bases were never attacked, their preparations for D-Day were unhindered all because of the RAF's protective cocoon. The US Navy's experience in the Pacific was quite a bit different as they had to defend against air attacks and they had real problems with the F4F due to its very poor rate of climb. They began to emphasize rate of climb as a result.
In short a Spitfire I is a far better aircraft for the Battle of Britain than a Mythical Mustang with a Merlin III.