WWII aircraft armament machine guns and cannon

[44 AMP]

The .50 cal was designed to pierce the structural bearing skin of a monocoque construction aircraft and attack the components within.

Close, but I think it would be more accurate to say that the .50 cal (BMG) was discovered to be very useful for piercing the structural bearing skin of a monocoque construction aircraft, and attack the components within.

The .50 BMG was designed to be a heavy machine gun round for use against armored vehicles and other ground material targets. Its inspiration was the late WWI Mauser 13mm anti tank rifle. All metal monocoque construction in aircraft didn't become common until about a bit more than a decade after the .50BMG was fielded by the US military. Since the .50 proved to be quite good at tearing up not just the skin but the vital components within, it became the preferred US weapon for that use as the war went on.

[RC20]

Oh yeah, WWII fighter planes are one of my things. So here goes.

Yea mine too.

I did not read all the responses but I think something has been missed here.

First the US was the only one with a 50 cal of its type (higher velocity). It was adapted off of Browning's WWI offering.

The Brits has a 50 cal as well, forget what, but not the velocity of the Ma Duce.

The European powers were heading for 20 mm arena, the 303s and the 8 mm were fill ins. Keep in mind the 303 is an old and pretty lame round. 8mm better but its still not a heavy hitter in an aircraft.

The US did play with 20mm in WWII, the aforementioned Corsair was one outcome. We had 20mm ammo build problems, why it took them most of the war to sort out? Some weird stuff (see Allison engine)

Something to keep in mind, the US was a lot of fighter to fighter and small bombers.
The 50 cal was effective and you could carry a lot more ammo (more firing).

So you have that balance between 30 seconds of 50 cal vs 10 seconds of 20mm.

The install weight really favored the 20mm (bang for buck) but the ammo capacity favored the 50 cal. The 303 and 8mm were really pathetic, its a wonder they shot anything down.

So what did the Brits put in their bombers? Yep, 303. Hmmm. Japanese tended to 20 mm even if not the greatest velocity.

Why did the 20mm work in the P-38? Because the pilot could re-charge the gun (clear the jams). Don't forget the 37 mm of the P-39 and derivatives.

I think the right choice was the 50 cal for the US and it would have been a good choice for the Brits.

Germany did have a 50 cal, but they tended to jump to the 20mm. Kind of a, hmmm. They had very experience pilots and the US had tens of thousand rookies.
Personally I like the longer firing.

How many times did you read of a Spitfire running out of 303? That was the 8 gun version trying to compensate for lack of effective with quantity over a shorter period.

The 50 cal and the 20 mm combo for the Brits would have been a lot better than the mixed 20mm and 303. Weird decisions but maybe all they could get at the time.

Latter decisions not to get 50 cal for their 4 engine bombers seems dumb. Or go with 20mm.

All those deck mounted Orkleins for the US? The could clear a jam. In the end it was found that 3 inch was the best combo (with the VTF). Why? Quantity and effect against Kamikaze. 5 inch was better but not the best bang for the buck.

You needed more than 40mm to bring down a Kamikaze, but a 5 inch was too much boom when you needed more booms. Early on the 20mm and 40 mm were effective. Not when you needed to get a total stop.

To this day the US still goes with 20 or 25 mm now, but then the days of guns is pretty well gone (the F-35 has all of 2 seconds worth of ammo)

Rest of the world still keeps to the 30mm revolver cannons.

Also keep in mind, rate of 20mm fire was pretty high.

Allison Engines: This is one that has long bugged me. Good book out on it by the way. Upshot was the Allsion was developed for the Army Air Corp (AAC)

The AAC was enamored with Turbo Chargers (vs a mechanical driven Super Charger).

The two fighters they made it work in was the P-38 which had a natural layout to accommodate a Turbo Charger (all those heat issues). The P-47 was just huge and the Turbo was in the back.

Bombers had no issues with a Turbo behind the Radials (the USN went with two Super Chargers).

The AAC would not let Allison develop multi stage or multi speed Super Chargers.

So what does the AAC pick? P-51 with a Merlin engine that used two stage or two speed (think both at various times) Super Charger setup. That and that alone was the power advantage of the Merlin over the Allison.

The Allison was simpler, they got more proven hp out of it (the AAC would not let them use or list it). The Brits did not care, whatever it took to win, worry about wear latter (the Merlin was not tested to the same high standard the Allison was)

The Allison given the same setup as the Merlin put out more reliable hp. It last a heck of a lot longer on the aircraft.

The Allison was modular so it could be fitted with any combo of aux stuff needed where it was needed.

The P-40 was a far better righter than its been given credit for (built into 1944 by the way)

What no one could do with any aircraft was slow turns with a Zero. Chenault had it figured out and his guys did gangbusters with the P-40 early on. It did well latter once the pilots got over you don't dogfight a Zero. But what were they trained to do? Dogfight an equal aircraft (P-40 vs P-40) and it was the man o man o best pilot wins.

The tactic that worked against the Zero was a high speed dive that got its controls stiff, then a turn (200+ mph, 250 better).

US never did develop a great non Gatling 20mm (or took them so long that not relevant). F-86 with its gunsight could have used the 20mm, but they could not get the 20mm not blow out the engine when firing (or too late).

I think the 50 cal was the best US choice.

I never heard of a P-47 dumbed down to 6 guns. I know some Wildcats did that to 4 guns. Made sense as more ammo and less weight vs Japanese fighters (Zero or the Ki-43 (Oscar).

The Zero;/KI-43 had a climb advantage early on as well, so the Wildcat and P-40 were not going to play in that part of a fight. Latter US fighters could go faster and climb better.

[Pumpkin]

The Italians had some decent fighters but they had pitiful guns.

Not sure if the P-47M, the hot rod had 6 or 8 50’s?

It was reported to have gone close to 500 mph with its 2,800 hp.

[davidsog]

Close, but I think it would be more accurate to say that the .50 cal (BMG) was discovered to be very useful for piercing the structural bearing skin of a monocoque construction aircraft, and attack the components within.

Just piercing the skin doesn't do much at all in terms of weakening an aircraft.

[Pumpkin]

I can't seem wrap my head around the 50 being ranked with the 303.

How did the Brits ever survive the Battle of Britain?
Yes the USAAF had overwhelming numbers towards the end of the air war but the British did not during the Blitz, the Germans still had some of their best pilots at this time. Hell even the Bf110 escort fighters had to be protected from the 8, 303 gun Spitfires and Hurricanes with Bf109's.

And from the report, how does aluminum skin protect critical internal parts from multiple 50 cals? It boggles my mind!

Was all the P-51,P-47 and P-38 gun camera footage altered?
I'm sure most of us have seen Axis fighters getting wings shot off and such.

Maybe I'm missing something, wouldn't be the first time.

davidsog,
My questions mean no disrespect for your obvious wealth of experience and knowledge on this topic.

[davidsog]

I can't seem wrap my head around the 50 being ranked with the 303.

Outside of both being rifle calibers, I would say the .303 is being ranked as the same as the .50 cal BMG is not valid nor is that the conclusion of the Allies. There is a huge difference. .50 Cal API had twice the penetration of the RAF's .303 AP round and four times the penetration of the RAF's .303 ball.

In fact, Post Battle of Britain, the RAF made a concerted effort to dump the .303 as it's primary fighter armament. That's why you have Hispano cannons being adopted to the Spitfire and Hurricane. IMHO, The 20 mm Hispano is only bested by the MK108 as the best air to air combat armament of WWII. The MG151 when equipped Minengeschoss is a very close contender slightly behind the Hispano.

.50 caliber BMG served the whole war and even equipped our first few Jet Fighters although post war its effectiveness was more the result of the K14 gunsight improvement.

And from the report, how does aluminum skin protect critical internal parts from multiple 50 cals? It boggles my mind!

It's not just aluminum skin. There are structural trusses to the airframe not to mention having to penetrate self sealing fuel tanks which are very thick. IIRC, .50 cal would penetrate the tanks and end up in the fuel. Since there is no oxygen in the tank, the fuel would extinguish any incendiary that made it thru, and the sealing function of the tank would simply seal behind the bullet as it entered. Most fighters have multiple control cables to each surface, the cables are noted as being very small targets with a low probability of a hit and an even lower probability of hitting enough of the cabling to disable the controls. .50 caliber could not penetrate the pilots armor which should not be a surprise as that is exactly what that armor was designed to do.

The test is also from a Zero degree deflection angle which means it is directly behind the target aircraft. That is the hardest angle to achieve an immediate shoot down in terms of causing damage to a fighter. The farther you get from a zero degree deflection, the easier it is to reach vital components including the pilot.

Was all the P-51,P-47 and P-38 gun camera footage altered?
I'm sure most of us have seen Axis fighters getting wings shot off and such.

No, it wasn't altered. .50 caliber could blow wings off it is hit the right components at a deflection angle it could reach them. Late war Bf-109's moved the pilots Oxygen tanks to the wings and that's not to mention ammunition boxes full of gunpowder or other ordinance. .50 cal would have to hit something explosive or flammable to cause such damage. Cannons brought their own explosive to the target and did not need to hit anything explosive to work.

Here is some vulnerability testing of German Fuel tanks against .303...

[davidsog]

I think that conclusion on the "slight contamination" of the fuel by being trounced with .303 incendiary rounds is a great example of dry British humor, LOL.
No sarcasm as all with "unlikely to cause any appreciable adverse effect on the running of the aeroplane engine".

[davidsog]

Not sure if the P-47M, the hot rod had 6 or 8 50’s?

P-47's could go with 6 or 8 guns.

Infact, the normal weight and balance of a P47 does not reflect the two additional guns, only 6.



It was delivered with 8 but did not have to operate with all 8.

[Pumpkin]

I know that humor quite well

My Grandad was on the HMS Pandora submarine during the war. Joined the Navy when he was 14.
As luck would have it he had to have an emergency appendectomy the day before she was sunk.
Never came to the states, was too scared to fly!

Edit: Didn’t the Brits have some of the higher octane fuel in comparison to the other combatants?

[davidsog]

Yeah, I don't think any Hurricane pilot would have taken much comfort in the fact dumping a burst of .303 into a He 111 fuel tanks could "slightly contaminate the fuel".

[davidsog]

HMS Pandora participated in Operation Catapult. What a desperate time that must have been for all.

At 1126A/4, HMS Pandora, off Algiers, sighted three destroyers 065° about 1 nautical mile from the shore, but she was unable to get within range. Three and a half hours later (1458A/4), however, she sighted a French cruiser thought at that time to be of the La Galissoniere class. In fact it was the sloop Rigault de Genouilly. HMS Pandora turned immediately to a firing course and at 1507A/4 HMS Pandora fired four torpedoes from about 3800 yards. Two certain and one probable hits were obtained. The French ship stopped at once and soon after she was observed to be on fire. Closing in HMS Pandora saw that there was no chance this ship could be saved. At 1632A/4 she was seen to sink by the stern and a few seconds later an extremely heavy explosion occurred, probably her magines blowing up.

HMS Pandora saw quite a bit of action:

https://uboat.net/allies/warships/ship/3404.html

I bet your Grandad had some stories. God Bless Him.

[davidsog]

Didn’t the Brits have some of the higher octane fuel in comparison to the other combatants?

Yes they did at times. It kind of ebbed back and forth. It's very hard to compare the German Synthetic fuels with Natural Petroleum Fuels on the Allies. C3 for example is more like a light oil with a distinct smell of coal dust. The Smithsonian has several hundred gallons in the wing of a JU388(I think...it may be a 288). We got some and sprinkled around the cockpit of one restoration for an "authentic" smell, lol. You can look at the Aircraft POH's to see what fuels they used. Airplanes are very specific in their maintenance and operation.

[Pumpkin]

Thanks for the link and the kind words.

[44 AMP]

How did the Brits ever survive the Battle of Britain?

Churchill gambled on Hitler's ego, and won.

What he "won" was the death of large numbers of British civilians and the destruction of large parts of many cities, which became known as "the Blitz".

And, you did use the correct term, England did not "win" the Battle of Britian. They survived it. Barely. In practical terms, they held the field, but did not destroy the enemy, and they took a terrible pounding in the process.

Some of that can be laid directly at the feet of those in charge. Doing a bit of research, you can find a number of things which British writers generally under report, gloss over, or simply ignore.

As to the "ineffectiveness" of the .303, particularly in the opening weeks of the Battle of Britian, (there is information explaining this, rarely mentioned by British historians) is a result of directives from RAF Air Marshal Dowding.

Dowding did not (at the time) believe that AP and incendiary ammo was needed to shoot down aircraft, and did not promote or authorize its use.

So the RAF went into the Battle of Britian shooting (mostly) ball ammo. The other factor that seriously hampered the effectiveness of RAF fighter was the "Dowding spread". Orders from RAF HQ had the planes guns set to converge in and 8-10ft circle at 300 yards. This, naturally meant that the guns effectiveness was not a great as what was possible, but those were the orders, and it wasn't until individual squadron commanders decided (if they did) to disobey/disregard the standing orders from HQ and had their guns regulated to what they felt best, and began using AP and the de Wilde incendiary ammo that the effectiveness of the .303 guns improved considerably.

This began to happen during the Battle of Britian, and as combat results proved it superior, became the general practice.

Another point mostly overlooked is that the cannon armed BF 109s were only about 50% of the Luftwaffe fighter force at the beginning of the Battle, and rose to about 60% during the course of the campaign. The twin MG twin cannon E-4 variant gets all the press, but reality is there were also a lot of MG only 109s in combat at the time.

Remember that the Battle of Britian was the first truly large scale, and long range (for the time) aerial combat of the war. Both sides found out where pre-war doctrine, tactics and equipment was found to be flawed and lacking.

Luftwaffe tactics in the opening weeks of the battle specifically targeted RAF fighter command airfields defending southern England, and they go hit, hard. To the point where senior commanders (privately) admitted they were as little as a week away from becoming combat ineffective.

Then, a "miracle" (for Fighter Command) happened. At this time, both sides did their best to only attack military targets. The London docks and arsenals were valid military targets, but urban London was not.

During a night bombing mission a flight of German bombers got "lost" due to faulty navigation, thought they were nowhere near London and jettisoned their bombs before heading home. They were, in fact over urban London and the bombs fell on civilian homes. (the pilots, were recalled to Berlin and punished for their error though it mattered not a bit to anyone but the pilots)

Churchill saw his opportunity and took it. He ordered the RAF to bomb Berlin, which they did, the next night. It wasn't a large raid, and had no real military significance, but it did what Churchill counted on, it enraged Hitler, who ordered the Luftwaffe to change its priority from attacking RAF airfields to bombing British cities, and that bought the RAF the breathing room to rebuild, replace losses and train more pilots which they desperately needed.

There is a lot more to it, of course and there are many fine books detailing the events thoroughly, but in a nutshell, it was Churchill's "gamble" and Hitler's response retargeting Luftwaffe attack priorities as a result, that "saved" Fighter Command at the cost of civilian casualties that allowed the RAF to stay in the fight, and so it "saved" England and "won" the battle.

Always keep in mind that from 1940 on, each segment of the war, year by year is a different situation, and the aircraft, armaments and tactics evolved and improved should be viewed in its own time frame, relative to what they could do, what they did, and what they faced.

[davidsog]

Both sides found out where pre-war doctrine, tactics and equipment was found to be flawed and lacking.

Very True except in one key area...Logistics.

The British had a phenomenal logistics systems they emplaced in the 1920's. It allowed the RAF Fighter squadrons to maintain near 95%-85% aircraft strength in their units throughout the battle. Meanwhile, the Luftwaffe Geschwader experienced strengths down to 70% aircraft strength and in some cases much lower.

The RAF established a three fold logistical system that replaced damaged aircraft overnight with fully operational planes because the Squadrons did not "own" the aircraft and subsequently had almost no in house maintenance assists.

The Luftwaffe Fighter Squadrons were equipped and responsible for almost all maintenance. So when a Luftwaffe fighter got damaged, it was out of the fight but still on the Squadron books and unavailable to be flown until it was fixed.

The Battle of Britain started with The RAF having a slight advantage in numbers of Single Engine Fighter Forces and ended with England outnumbering the Jagdwaffe.

Like Rommel said, "Amateur's study tactics, professionals study logistics."

Battle of Britain was lost long before the Second World War started. Luftwaffe doctrine, so successful in establishing a powerful synergy between air and land operations, was deeply flawed in its understanding of the fundamentals of air power.......

But the possibility of a Luftwaffe victory was effectively compromised by plans laid down in the pre-war period that provided Fighter Command with a quantitative advantage, and the means to sustain this advantage, denied to their opponents.

What makes this all the more surprising is that Fighter Command’s operational losses were significantly higher than those suffered by the Luftwaffe’s fighter force.

it is evident that Fighter Command steadily fielded more single seat fighters as the Battle progressed. In fact, as the Royal Air Force grew stronger so the Luftwaffe grew weaker.3

From the Royal Air Force Center for Air Power Studies:

https://www.raf.mod.uk/what-we-do/ce...l3-iss4-2-pdf/

[44 AMP]

I just recently read that, due to the efforts of Lord Beaverbrook, the factories were supplying about 100 fighters a week to the RAF during the Battle, but this is just aircraft.

Where the RAF had its biggest shortfall was in trained fighter pilots. Those are not as easily replaced as aircraft.

Many of their pilots had only 10-12 hrs flight time on the Spitfire when they went into combat.

To keep going, the RAF transferred in Bomber command pilots and created the Polish and Czech squadrons, who while they did need training on Hurricanes and Spitfires were better than new recruits, as they already understood basic flying skills.

And once the constant direct pressure on the airfields and command facilities was reduced by the shift to bombing cities and fighters tied to escorting the bombers, the RAF was able to recover, and then continue to expand.

[2damnold4this]

David, do you have a link to the original paper you are citing that mentions "0.50" B. Mk II"? I'd like to know exactly what bullet they are testing and what gun was used.

0.50" B. Mk II sounds like Vickers Mk. II ball fired from a Vickers 0.50 which was significantly less powerful than a BMG.

I'd love to see a link to the full paper so we could tell exactly what the British were testing.

[44 AMP]

Outside of both being rifle calibers, I would say the .303 is being ranked as the same as the .50 cal BMG is not valid nor is that the conclusion of the Allies.

Just looking for some clarification of your definitions, your opinion is that if it doesn't fire exploding projectiles, its not a cannon, its "rifle caliber". Is this correct, or am I misunderstanding your viewpoint?

Where would you put the Italian 12.7x81mm ? It is a .50 caliber round, with a smaller case and less power than the .50BMG, but it had a HEIT (High Explosive Incendiary Tracer) round.

OR, for that matter, where do you put "cannons" that don't fire explosive shells, such as early war tank and anti tank guns that fired only solid shot?? Not an aircraft gun, I admit, just curious if you would consider something like the British 2 pounder (40mm) a cannon or a rifle caliber gun??

[RC20]

What is being missed, pilots armor protects the pilot, not the aircraft.

The 50 Cal was designed to penetrate armored vehicles, you have to question test methods when it supposedly did not penetrate cockpit armor.

And........... what happens when a round hits armor inside a fuselage? Yep, it takes another route, tumbling and ripping as it goes.

the Pilot in theory would survive, the aircraft would be ripped up badly if not destroyed.

20 mm exploded, but you had to time the explosion right to be effective.

Really some of some and the 50 cal was effective both in WWII and despite issues with Migs, it knocked a snootfull out of the air. You had nose concentration.

Contrast with Mig 15 designed to knock down bombers with big guns and slow rates of fire not a hot maneuvering F-86 (and shot down by Corsairs and stragiht wing jets too - bad pilots depending on what stage of the war.

[44 AMP]

The armored vehicles the Browing .50 was designed to defeat were WWI tanks, and the next generation in the early 20s. It proved able to defeat up to half inch armor plate (hardened, not just the "boilerplate" steel of WWI tanks), within certain range and angle of impact limitations.

During WWII air combat was rarely a point blank situation, though there were a lot of "close range" engagements, close range for 300+mph aircraft is a couple hundred yards and longer engagement ranges were more common, meaning the round had lost measurable velocity. But not significant enough to affect its ability against aircraft, which are lightly built, other than the few spots they have armor, IF they do. Many of the WWII combat aircraft, did not have armor anywhere.

Despite the truth that on a single round vs round comparison cannon shells are more destructive, the massive impact of 4, 6, or even 8 .50BMGs firing into a small convergence area should not be dismissed or denigrated.

Firing more rapidly and at higher velocity than contemporary aircraft cannon, and with most of our fighters carrying from over 200 to over 400 rounds per gun it was highly effective.

Yes, the .50 was eventually replaced as main armament as the jet age progressed, even single seat fighter jets are larger than their WWII counterparts. Speeds got higher, engagement times shorter so rapid fire cannons and improved gunsights were adopted to maximize damage if only a few hits were made. The "Vulcan" class multi barrel powered guns replaced single barrel cannon, when technology reached that point, and today those guns have nearly all been replaced with air to air missiles for jet on jet combat. IF/when combat effective lasers can be fitted into fighter aircraft, I suspect they will replace missiles.

Combat in the air has its own version of the gun/armor race ground vehicles have, technology improves as time marches on.

[Jim Watson]

Then there was the period when air to air missles were The Cure.
They eventually put a gun in the F4, though.

ETA. The internal 20mm came along in the F4E.

[105kw]

Sadly, not in the Navair F-4s.
I never even saw a gun pod on an F-4B or J when I was in the Marines.
Apparently, they were a pain to get bore sited, then dialed in with the gunsight.

[Pumpkin]

I have quite a few “DUEL” books sold by OSPREY PUBLISHING and the most recent one is # 68, RAF FIGHTERS vs LUFTWAFFE BOMBERS Battle of Britain.

One account would be laughable if it were about a different subject; On August 16 1940 Spitfires of No. 602 Sqn intercepted some He-111s.

One Heinkel, the subject of this account was engaged using a beam attack.

The attack report showed that the Spitfire section had expended 9,000 rounds on the He-111!

An RAF intelligence report noted between 300 and 400 .303 bullet holes, with No Armor plating perforated!

To say some RAF fighter pilots wanted something better than the.303 is probably an understatement. The much awaited 20mm equipped Spitfire VB finally started showing up in 1941.

[105kw]

The first cannon armed Spitfires were Mk1b aircraft, that were assigned to 19 Squadron.
There were only about 12 aircraft, and the were on operations by August of 1940.
They were pulled of ops, due to gun jambing problems.

The Mk2b, cannon armed Spitfire, came in to service by late 1940. Numbers were limited, about 170. Apparently they solved most of the reliability issues.

The Mk5 was introduce in early 1941, a few were made in the A wing with 8 machine guns. Most were B wing with 2, 20mm and 4, 303s. They were still hampered by a 60rd drum magazine. The Mk5c, in 1942, had a 120rd box magazine. And could carry 4, 20mm cannon.

By the way, a lot of 8, 303 armed Mk1, and Mk2s were re-engined into Mk5s. And some served in combat into 1943.

[44 AMP]

The attack report showed that the Spitfire section had expended 9,000 rounds on the He-111!

An RAF intelligence report noted between 300 and 400 .303 bullet holes, with No Armor plating perforated!

which means that about 96% of the rounds fired, missed. You can't blame the cartridge, or the guns for that. Nor can you really blame the Spitfire aircraft.

The first significant combat between RAF Spitfires and the Luftwaffe was over Dunkirk in the last week of May. A couple months of mostly intermittent combat ops is not a lot of OJT training in something that is learned on a personal, individual level. Flying is training, tactics can be taught, what works and what doesn't can be taught, but being able to DO it is something only experience teaches.