Japanese Zero vs Spitfire vs FW 190

pinsog said:

I agree with what your saying. I've said in other threads that the Whirlwind should have had 8 30's in the nose with 30 seconds of ammo instead of the 4 20mm. 8 30's that concentrated would be like a mini gun.

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One of the prototypes had 12 machine guns.

re: armour in aircraft structure -- here are some figures from a Dec 1940 trial to illustrate the point

Keeping in mind the document Glider posted above (.303 AP is able to penetrate 9 mm of armour at 200 yards, 0 degrees).

In firing trials on a Spitfire fuselage (200 yards direct astern), 39 rounds struck the projected area of the pilot's 4-mm armour plate.

• 17 rounds were deflected/stopped and failed to reach the plate (44%)
• 5 rounds struck the armour and failed to penetrate (13%), 4 of these were fragments upon striking the armour
• 2 rounds (fragments) penetrated the armour (5%), only one of these penetrated the pilot's seat afterwards

EDIT: naturally doing some quick math I see that only 62% of the rounds are accounted for in the test summary. Not sure what to make of this. Perhaps the other 15 rounds were stopped by the equipment in the rear (radio, flare tube, etc.)?

Not sure.

In terms of the real world / operational differences of LMG vs. HMG

The main difference most often cited by aircrews and responded to by designers was effective range. The .30 cal weapons were very generally speaking considered relatively ineffective at more than 200 meters. How much this mattered depended in part on the number of guns and the nature of the guns - the Soviets for example had very fast firing 7.62mm LMGs which could cause a lot of damage, but as a rule they tried to get within 50-100 meters before opening fire anyway. The British famously put 8 x .303 guns on their fighters (later 12 guns on some) to concentrate firepower, so if they were in range they would likely kill their target quickly.

The .30 cal guns tend to spread out in a wider cone though which is part of the reason for the shorter effective range. Greater range meant fewer hits.

Americans were taught to do deflection shooting though only a few could master the skill - often guys who had a past history of hunting or some other kind of marksmanship. Most US fighters lacked nose guns and wing guns were not as accurate. One method they were trained to use was to use their wing mounted HMGs to shoot streams of bullets with tracers they could walk into their targets. Each pilot would work with their armorers accordingly to set range conversion of their guns based on their own preferences and marskmanship skill. There were a number of different options: all guns converging at 200, 250, 300 or 350 yards, or to have a pair of guns converging at three different ranges - one pair at 250, one at 300 and one at 350 for example, or a pair at longer range like 400 yards and the other four at 300.

But effective range for .50 cals was up to 500 yards or more, albeit with increasing challenges to accuracy. During a long stern chase range cold be almost double that. In one incident in North Africa for example an American P-40F shot down a Spit VC in a case of mistaken identity after a long chase, reportedly at a distance of 800+ meters (too far to identify what they were chasing). On another occasion J.G. 27 experten Hans Stahlschmidt was shot down from below at extreme range by Clive Caldwell. Caldwell himself said the distance was 700 yards, fellow experten Hans Joachim Marseille and Hauptman Homuth who were on the flight with Stahlschmidt both commented on the range of the hit.

The API .50 cal ammunition used by the Americans was initially just intended to mark the target - the little flash of a small amount of incendiary charge was an indication to the pilot that they had gotten a hit. The fact that this flash could ignite fuel, hydraulic fluid, oil and so on was an appreciated additional effect. Tracers had a similar purpose obviously but some pilots preferred not to use them because enemy fighters could avoid the bullet stream with a quick jink or slip when they saw the tracers coming.

.30 cal weapons were typically considered a problem vis a vis defensive fire from bombers - both for the bombers themselves and for fighters attacking them. One of the complaints I've read about the early LMG based armament of Spitfires and Hurricanes was that it put them within the range of defensive bomber gunners. This was worse if the bomber had HMG or cannon armament in their defensive panoply - like the G4M "Betty" (20mm tail gun) the later He 111 (13mm in dorsal or rear gun position), or the SM 79 in the Med (1 or 2 defensive 12.7mm MG in dorsal or ventral positions). And of course most of the US made multi-engined bombers had .50 cal defensive guns, and this was a big problem particularly for the lightly armed Ki-43.

Defensive armament consisting of .30 cals, .303, 7.9mm etc. was often considered insufficient due to having about half the effective range of the heavier guns, and was routinely increased to use HMG or cannon defensive guns where possible. HMGs could outrange LMGs particularly during a long stern chase approach. Most cannon could as well. Conversely fighters were up-gunned so as to outrange defensive gunners and to quickly take them out, especially if they were protected by armor.

The second biggest issue was armor and protected fuel tanks. Early war military aircraft typically lacked any kind of protection, it was gradually brought in during 1939-41, especially during the Battle of Britain. Early armor was however often quite light, average probably about 8mm of unhardened steel. Sufficient to stop most .30 cals but not HMGs or cannon with AP ammunition. Also after armor was adopted, many other systems such as fuel lines, hydraulic lines, control cables and others were vulnerable to a stray bullet. It took a while for redundancy to be built in so as to decrease vulnerability. They also started putting in thicker armor of up to 12-15mm, and then later tempered / heat treated plates which could be just as strong for half the weight (so a 6mm plate was equivalent to a 12 or 13mm plate).

Aside from range, another factor which could make a big difference was angle of attack. This was true for all types of guns but it made LMGs potentially much more lethal. With Zeros they had an infamous trick where, when pursued from behind they would suddenly jump up into a loop that their pursuer could not follow, then come down onto their attacker from behind and above, and shoot right into the cockpit. This was more lethal with the 7.7mm guns concentrated in the nose of both A6M and Ki-43. Shooting from above in this manner allowed the attacker to bypass the armor and kill pilots or puncture fuel tanks. This kind of high angle attack was also incidentally done by Hans Joachim Marseille when attacking Allied fighters flying in defensive Lufberry circles over North Africa. The plexiglass cover on most aircraft offered zero protection to the pilot. Spitfires and Hurricanes also had fuel tanks in front of the cockpit.

Another method used frequently by the Japanese (and by everyone, really) was to spot an aircraft with an oblivious pilot flying straight and level, dive below it and come up from underneath, shooting into the belly from close range. This was a good way to kill the pilot as above but also to shoot holes in the coolant systems of in-line engined aircraft or damage the oil coolers and so on. Again, from close range, at the oblique angle, an accurately aimed LMG could easily kill almost any Allied fighter.



Finally, one can always find anecdotes where the 20mm cannon shells did not bring down the fighter. There was a great deal of luck involved but also how much time the attacker had to score hits, and how close of a pattern they managed.

Here is one I've posted before, Clive Caldwell posing with his Tomahawk after a tense fight with JG. 27 experten Major Werner Schröer and his wingman. Caldwell managed to shoot down the wingman and damage Schröers fighter enough to escape, though he was wounded in the back, shoulder and leg (probably with shell fragments). You can see what look like at least three cannon hits in the right wing.




This one is a US pilot of the 79th Fighter Group examining a 20mm shell hole, one of about 8 that hit his P-40 from a Bf 109. Obviously his behind the seat armor plate saved him.



A crash-landed P-40K of the 57th FG, also in North Africa with 20mm cannon holes near the cockpit. The pilot survived with minor injuries.




A Bf 110 damaged (IIRC) by Spitfires, gives you an idea how the cannon could tear apart an aircraft. One or two more hits on that tail structure and it would have come off.


And for comparison, an He 111 damaged by a hail of .303 bullets (I think) in the BoB

The Bf 110 was hit by Soviet AA according to this...Messerschmitt Bf.110G-2 with traces of damage from the Soviet anti-aircraft fire

fubar57 said:

The me 110 was hit by Soviet AA according to this...Messerschmitt Bf.110G-2 with traces of damage from the Soviet anti-aircraft fire

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Fair enough, I knew I'd seen the image before but I wasn't sure (hence the IIRC). It does show the effects of cannon fire though right?

re: the bottom photo, I think it was deduced from the uniforms that the Heinkel was brought down by Swiss MS 406s.

Lol I should have left those last two off...

pinsog said:

1 round, 50 bmg into a 55 gallon barrel of water. Imagine if that is a fuel tank on an airplane. Just punching through armor doesn't tell the whole story of the superiority of the 50 bmg over any 30 caliber bullet.

30 caliber bullets just poke a small hole.

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A .50 Browning weights 40kg, the .303 Browning 10kg, 100 rounds of 50 is 16kg 100 rounds of .303 2.5kg, all weights are give or take because different ammunition has different weights but it's close enough for this discussion. For the weight of one .50 you can have four 30's, with hundreds of rounds of extra ammunition as well as many more rounds going downrange per second burst, yes they are smaller but the .303 had reliable AP Incendiary tracer rounds in production in 1940, the .50 didn't. It's also important to remember that available engine power played a big part in what gun and ammunition load could be fitted.

Schweik said:

And for comparison, an He 111 damaged by a hail of .303 bullets (I think) in the BoB

View attachment 563179

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I don't know whether that was the BoB or not but the loss rates are skewed in the BoB by many planes that made it back to base and never moved again.

PAT303 said:

the .303 had reliable AP Incendiary tracer rounds in production in 1940, the .50 didn't.

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The .303 had BOTH Incendiary rounds AND tracer rounds, they were separate rounds. During the BoB there were not enough incendiary rounds and only 1 in 8 rounds fired was incenderaily. This might have change as the battle progressed?

The .50 cal may have had a tracer, it did NOT have an incendiary round until some point in 1941 or 1942.

Tracers make lousy incendiary rounds because the incendiary material is ignited upon firing and burns from that point on. the longer the distance the less incendiary material is delivered to the target.
The British used 3 different tracers from 1939 on (and perhaps some older stuff) although later in the war some new types were introduced.

The main one was "Tracer G MK II" and used 10 grains of tracer compound and had a bright tracer to 1000 yds at which point there was little or no tracer compound left.
The Navy in 1939 also adopted the "Tracer G MK III" which used 10 grains of a different compound for brilliant trace to 800 yds.
Bomber command also got into the act in 1939 with Tracer G MK IV" which used 4.5 grains of the compound used in The Tracer G MK II for a trace lasting to 40O yds (later 600yds) as an aid to range estimation for the defensive gunners. The round was issued in 1940 and was good for 550 yds of trace at 10,000ft.
The Incendiary B MK VI used 7 grains of incendiary compound which only ignited on impact.

Early British .50 cal tracer would give a red trace to 2000yds.
The British did not consider the American M1 .50 Incendiary round to be bore safe although small quantities were supplied in 1940. A new, redesigned Incendiary was considered high priority. Service quantities (some trials ammunition earlier?) do not appear to have shown up until late 1941.

It is quite possible to set fires with tracer ammunition. But since that was not it's intended function relying on it to do so may require a lot of hits.

I would note that 20mm cannon ammo was highly variable in it's target effect since they was a considerable variation on the amount of HE (or incendiary) that different shells carried.

What is the fluid leaking out from behind the cockpit on Caldwell's plane?.

Oil or fuel

Schweik said:

Oil or fuel

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What's oil or fuel doing up in the turtledeck? Isn't that where ADI fluid lives?

There are hydraulic tanks in that area of the rear fuselage on early P-40s (maybe on the later ones also but I do not know).

PAT303 said:

During the BoB it was normal for standard MkVII ball to be loaded in three of the guns because of a lack of aircraft specific ammunition, they didn't help the LMG's reputation. The RAF would have been better off putting resources into producing specialist ammunition once war was inevitable, tracer in particular in light of the poor overall shooting standards of the day but it's easy to make decisions in hindsight.

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I've never come across anything that indicates Ball was used due to issues with supply. Due to pre-war testing the British found that overall there was little to choose between Ball and Armour-Piercing under average conditions. AP being more effective vs. armour, heavy fittings and engines but also more easily deflected, slightly less accurate and caused rather heavier barrel wear.

Tracer gave a misleading indication in fixed-gun air-to-air sighting and therefore wasn't a requirement.

The main Incendiary in use (Mk.IV) was known to be unsatisfactory and full effort was underway in replacing it with the new Mk.VI.

The armouring of LW aircraft and the express orders to Fighter Command to target the engines of enemy bombers no doubt led to the complete replacement of Ball by AP in RAF orders (November 1940).

There was no adi fluid used in the P-40.
The oil tank moved around. Behind the engine on the P-36, behind the pilot and over the rear fuel tank on the long nose P-40s, back to in front of the pilot on the P-40D/E and later.

Schweik said:

Anyway there seem to have been mistakes made with the Spitfires shipped over from the UK. ..... Gun heaters were either disconnected or not installed. Both of these issues were discovered after they caused serious problems in combat. .

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People tend to think that the tropics are hot and therefore icing will not be a problem. The reality is that the very high humidity means that icing is a serious problem and extends far higher than in temperate and cold weather climates.

Schweik said:

Here is one I've posted before, Clive Caldwell posing with his Tomahawk after a tense fight with JG. 27 experten Major Werner Schröer and his wingman. Caldwell managed to shoot down the wingman and damage Schröers fighter enough to escape, though he was wounded in the back, shoulder and leg (probably with shell fragments). You can see what look like at least three cannon hits in the right wing.

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MAW vol. 1, page 252-253, describes the combat rather differently. Caldwell was jumped by Schroer and his P-40 lit up, but the flames died out so he stayed with the plane.
Schroer returned to base without damage and no losses to his unit.