Best armed fighter

[HoHun]

Hi again,

>Last edited by claidemore : Today at 12:30 AM. Reason: (against bombers)

Oh, that wasn't in your post when I clicked "reply".

>This belief that .50s were ineffective (against bombers) [...]

With the addition, I see your point - in fact, it's the exact mirror image of the common misconception that cannon are effectly only against bombers.

Regards,

Henning (HoHun)

 

[KrazyKraut]

The Condor is a converted airliner and Me323 is a transport. Both don't fly in tight formations, both don't have a very impressive defensive capabilities. Attacking them is much easier and doesn't require dealing as much damage as possible in as little time as possible. At least not even nearly as much as a flight of B-17s does. Especially the Fw 200 was usually a complete loner.

 

[Glider]

On the subject of .50 BMGs shooting down heavy bombers, I believe the Royal Navy Martlet I/Wildcats (with 4x.50s) shot down several FW200 Condors, a heavy 4 engine bomber. (as renrich pointed out).

The Condor was a converted passenger airliner with a weak spot in the rear of the fuselage. It wasn't built to stand the strains of battle as any normal bomber would be making it vulnerable.

.

Me323's also fell victim to P40's in North Africa, (I believe James 'Stocky' Edwards got 2 or 3 in one mission?)

There were also a host of twin engine bombers that fell to .50 Browning, both German and Japanese. .

Absolutely true

Also, Anabuki Satoru shot down two P38s and two B24s with the twin 12.7mm guns on a Ki-43 (then rammed another B24 to become an "Ace in a Day") .

This should be treated with more than the usual amount of caution. The combat happened on the 8th October 1943. The 495th Fighter Unit which was the only P38 equipped unit in India or Burma, didn't fly its first missions until 21st November. Secondly no B24's were lost in the combat zone on that day. Thirdly to expect one Ki43 to achieve this level of damage with 2 x 12.7mg's with their limited ammunition of 250 rpg is asking a bit much. There was some scepticism of his claims by some of the other Japanese Pilots

That said it is only fair to say that the Japanese did shoot a number of four engined bombers with the Ki43.

 

[Juha]

Hello
Yes I know the FW 200 kills by Martlets/Wildcats but still the main adversarities of RN fighters were many time lone snoopers, so 6*.5s with fewer rpg made sense to it. After all, even if FC shot down hundreds of medium bombers in 1940 with 8*.303s it demanded 20mm Hispano armament for its future fighters.
BTW IIRC the first ever a/c destroyed by Martlet/Wildcat was a Ju 88 shot down by a RN Martlet pilot.

Gliber
my recollection is also that Anabuki's claims was badly inflated.

Juha

 

[Timppa]

In choosing the aircraft armament, aspects such as war economy, production, contracts and even nationalism probably played big part.

Germans used rifle caliber guns (7.7mm) quite late, Bf109-G4 and Fw190A-6 still carried them. Spitfires, even the XIV, carried .303 guns to the last day. In America, 20mm cannon was only in limited production, perhaps also due to the fact that it was NIH (Not Invented Here), having French and British origin.
The Soviets seemed to be most flexible. Having the best rifle caliber MG (ShKAS and Ultra-ShKAS) and best heavy MG (UBT,UBK,UBS), they replaced them quickly after discovering that the cannons offered still more 'bang for the buck'.

 

[HoHun]

Hi Juha,

>Yes I know the FW 200 kills by Martlets/Wildcats but still the main adversarities of RN fighters were many time lone snoopers, so 6*.5s with fewer rpg made sense to it.

Just to make sure: If you had the choice of cannon, it never made sense to use the 12.7 mm Browning M2.

It always loaded your aircraft down more than any cannon battery, with all the inevitable negative consequences on performance and manoeuvrability this brings.

Here is the well-known comparison repeated for yet another aspect, equal ammunition capacity:

6x ,50 Browning M2 - 240 rpg, 18 s duration - 332 kg - 1,7 MW firepower - 31.4 MJ total supply
2x Hispano II - 150 rpg, 15 s duration - 174 kg - 2,1 MW firepower - 31.8 MJ total supply

It's amazing how often I can post facts and figures in this thread just to get the same old "but for XY, the fifties were good enough", with XY being everthing from "fighters", "Condors", "mounting it on a tank" or "mounting it on a ship". The only one that is missing is "using it as a boat's anchor", and that's almost the only honest assessment in a discussion of aircraft armament.

Regards,

Henning (HoHun)

 

[claidemore]

Question:
The second series of Mustangs, the Mk1A's, were armed with 4 x 20mm Hispanos, and were in combat from 1941 until well after D-Day.

Why did the subsequent models go back to the .50 Brownings? Since the RAF already had success with the Hispano, in both Spitfires and Mustangs, why didn't they put them in the MkII, MkIII etc?

Anybody?

Claidemore

edit: interesting pic of Mk1as
Mustang Ranch: 1942 | Shorpy Photo Archive

 

[HoHun]

Hi Claidemore,

>Mustang Ranch: 1942 | Shorpy Photo Archive

Great picture, thanks!

>Since the RAF already had success with the Hispano, in both Spitfires and Mustangs, why didn't they put them in the MkII, MkIII etc?

I can only speculate, but during the war there was considerable drive towards standardization between the different services and between US and British users. As the USAAF was unlikely to adopt the Hispano cannon (since the US models had serious problems), the RAF probably had to accept standardization on 12.7 mm armament.

Regards,

Henning (HoHun)

 

[renrich]

In my mind there is no question that two 20 mms in the wings, if they have ballistics similar to the the US 20 mms in Dean's book, are going to be more effective than four or six 50s in the wings. That is, they will be if the pilot can hit the target with them. If the ballistics are similar to the A6M's 20 mms then I believe the four or six fifties are more effective. The two issues are; can the target be hit equally as often with the two 20mms as with four or six fifties and do the 20mms have a flat enough trajectory and high enough velocity to allow them to be easy to hit with. The only other issue is ammo load. In the case of the A6M, the cannon had a low MV (and I suspect a poor ballistic coeffiecient) so they were a short ranged weapon and had a low ammo load. Those characteristics made the Wildcat a better armed AC. To boot, the early A6M had no armor and no ss tanks which made it not very resistant to 50 cal fire. It seems to me that, in a theoretical case, if one fighter has two guns and the other has four or six guns and the trajectories, velocities and rate of fire are the same, the fighter with four guns is twice as likely to get hits as the fighter with two guns and the fighter with six guns will get proportionately more hits than the other two. If the MGs have a higher rate of fire and higher velocity and flatter trajectory then that will increase their chances of getting hits and if the MGs have a longer firing time due to a greater ammo load then the chances of getting hits is increased more. The factor which then comes into play is the amount of damage each hit causes. In the case of the 303 British, if memory serves, their boffins postulated that it would take a two second burst with eight guns which would yield 397 hits(?) to bring down a bomber. In the case of the Rheinmetall 30 mm MK103 cannon the German boffins predicted that from 500 meters 40 hits from that weapon would bring down a four engined bomber 50 % of the time and 76 hits would bring it down 95% of the time. Between those two extremes would fall the performance of the 50 BMG and the 20 mms. Would each hit with a 20mm be twice as damaging or would that depend on where the hit occurred? My personal experience with the 50 BMG is that it has great destructive capabilities on ground targets such as trucks, half tracks and personnel carriers and my personal experience with airplanes(having owned a 172 and flown an L39) is that a similar sized WW2 fighter is not as robust as a two and one half ton truck. Having said that a 20 mm, if it hits and wherevever it hits, has got to do more damage than the 50 cal round. Hmmmm?

 

[KrazyKraut]

Uh 40-76 hits by an MK-103 to bring down a bomber? How does that fit into the picture when at the same time 3-4 hits by the similar or slightly weaker MK-108 were considered enough? Or ~25 hits of the definetly weaker MG 151/20?

 

[renrich]

Good point. I am quoting from a book entitled "The Great Book of WW2 Aircraft" and this info is in the section on the FW190. I suspect that the table is meant to show the probability of getting enough hits with the rounds expended to cause fatal damage. The table indicates that it is a 50% probability that 104 rounds from 1000 meters and 308 rounds from 1500 meters will bring down the bomber.

 

[KrazyKraut]

Yes, I would assume you mean 40 to 76 shots fired from an MK-103 to bring down a bomber with the probabilities quoted, that makes sense.

 

[HoHun]

Hi Krazykraut,

>Uh 40-76 hits by an MK-103 to bring down a bomber? How does that fit into the picture when at the same time 3-4 hits by the similar or slightly weaker MK-108 were considered enough?

It's actually 76 rounds fired for a 95 % probability of kill, achieving 10 % hits at a medium combat range of 500 m.

http://www.ww2aircraft.net/forum/weapons-systems-tech/30mm-mine-shell-15789.html

>Or ~25 hits of the definetly weaker MG 151/20?

18 hits for 50 % probability of kill. For comparison, another report equates 20 hits of 20 mm MG 151/20 with 75 hits of 15 mm MG 151 ammunition.

Since the MG 151/20 rounds were roughly twice as powerful as the 12.7 mm Browning M2 rounds, this would suggest something in the region of 150 hits or 1500 rounds fired for a 50 % kill chance on a heavy bomber.

This would equate to about 14 s of firing time for a battery of 8 Brownings, compared to about 5 s for a battery of 4 MG 151/20, making the bombers' return fire more than twice as effective against a Browning-armed fighter.

Regards,

Henning (HoHun)

 

[claidemore]

My math isn't that great, but.....if the MG151/20 is twice as powerful as the .50 Browning, and it takes 20 hits from the 20mm to down a bomber, then wouldn't it take 40 hits from the .50?

Looks to me like you might have doubled the 75 rds needed from the Mg151/15 to get 150 hits from the 8 brownings?

To get 40 hits from a 10% hit probability with 8x.50s you need just under 4 seconds of firing time.

 

[HoHun]

Hi Claidemore,

>My math isn't that great, but.....if the MG151/20 is twice as powerful as the .50 Browning, and it takes 20 hits from the 20mm to down a bomber, then wouldn't it take 40 hits from the .50?

Roger, that was a typo. It should have been:

"Since the MG 151 rounds were roughly twice as powerful as the 12.7 mm Browning M2 rounds, this would suggest something in the region of 150 hits or 1500 rounds fired for a 50 % kill chance on a heavy bomber."

So 75 hits required from an MG 151 with the original 15 mm calibre translate into roughly 150 hits required from a Browning M2 of 12.7 mm calibre.

The comparison of required firing times is correct as originally posted:

"This would equate to about 14 s of firing time for a battery of 8 Brownings, compared to about 5 s for a battery of 4 MG 151/20, making the bombers' return fire more than twice as effective against a Browning-armed fighter."

I chose the 4 MG 151/20 battery for comparison since despite the 15 mm cannon's good qualities (which the USAAF considered superior to the Browning M2), no Luftwaffe fighter ever used a battery of 4 15-mm-calibre MG 151 guns.

Regards,

Henning (HoHun)

 

[HoHun]

Hi Claidemore,

>With only 10-5% accuracy, convergence issues really aren't an issue at all, in fact they will probably increase hit probability with the 'box' harmonization. The less accurate system (sic), will be more effective in combat.

>[...]

>Basically a large 'box' harmonization of wing mounted guns would be capitalizing on the 90-95% expectation of missing the target, and turning that into a hit probability.

If that would be correct, we'd have seen the nose guns on fighters like the P-38 deliberately set up to diverge to reduce concentration of fire and increase effectiviness (as you suggest this would accomplish).

However, if you look at the bore sighting chart for the type, you'll see that the machine guns were only half a meter apart and set to fire parallel, and that the guns were carfully harmonized to converge in the vertical plane to give the highest concentration of fire possible.

There was nothing to stop the USAAF from increasing the size of the pattern of a nose-gun fighter, had they wanted to. However, they couldn't decrease the size of the pattern of a wing gun fighter for technical reasons.

That they didn't go for a large pattern when it was not enforced by technical reasons shows pretty clearly that they did not want the large patterns inevitable with wing gun fighters, but were stuck with them because there was no way to shrink them.

Regards,

Henning (HoHun)

 

[HoHun]

Hi again,

"If you look at the bore sighting chart for the type, you'll see that the machine guns were only half a meter apart and set to fire parallel, and that the guns were carfully harmonized to converge in the vertical plane to give the highest concentration of fire possible."

In order to illustrate this point, I used the above boresighting chart for the P-38 to create the attached animated GIF, showing the sight picture for a straight six, no deflection "boresight" attack (placing the centre of the crosshair right on the centre of the target) against a P-47-sized fighter.

Ranges start with 100 m and increase in 100 m steps to 1000 m maximum.

Thin-line circles are 100 % hit circle, fat-line circles are 75 % hit circle.

The 20 mm cannon is indicated in red, the 12.7 mm machine guns in yellow and orange.

Basically this is the same kind of diagram as I have posted above for the P-47 and the Me 109K, just in a more compact presentation.

It was still more complicated to assemble because instead of one pattern per (half) battery, the new diagram has one pattern per gun. Additionally, I found that the P-38 boresighting chart gives surprisingly flat trajectories for some unknown reason, perhaps because because it illustrates the situation at 30000 ft or something. For comparison purposes, I established sea-level trajectory data from speed-over-range diagrams for the 12.7 mm and 20 mm armour piercing ammunition, using 12.7 mm trajectory data provided by Tony Williams (from "Machine Guns" by Max Popenke and Tony Williams) to verify that my calculation is sound. (Tony's data: Flight time to 1200 m 2.04 s, my calculation: 2.00 s, Tony's data: mid-range trajectory +510 cm, my calculation: +491 cm).

Anyway, I think the resulting diagram illustrates the excellent qualities of the P-38 as a gunnery platform quite well!

Regards,

Henning (HoHun)

 

[claidemore]

Hi Henning,
Just wanted to point out that each set of 4 guns on a P47 are arranged in close proximity to each other (as in the P38 ). When they are not sighted for a 'box' harmonization, they will also give a good concentration of firepower, albeit with two 4-gun streams of projectiles with the attendant 'problems' of harmonization. At the harmonization range, there will be a double concentration of fire.

I agree that in a boresighting, on your six, no deflection type shot (as illustrated above), the P38 gun layout would be devastating. I just believe that in deflection shooting against a target that is moving on various planes, the box harmonized wing guns will have a greater chance of scoring a hit, and a hit of any kind is better than a complete miss with an overwhelming concentration of fire from nose mounted guns.

Of course it wouldn't make sense to box harmonize nose mounted guns on a P38, it would negate a tangible advantage, concentrated firepower, and the choice between hit probability and concentrated firepower is clear for that fighter.
On a wing mounted gun fighter the choice is not so clear. Concentrated firepower is less tangible, existing only at harmonization range, so a box harmonization does make sense, trading a less tangible concentration of firepower for hit probability.
Since the vast majority of fighter pilots did not aim for specific parts of their target, ie O2 tanks/fuel tanks, cockpit, but rather at the whole plane, and were still missing 90% of the time, the 'shotgun' box harmonization seems like a pretty good choice.
As was pointed out earlier, with the advent of computerized sights, nose guns are an obvious choice. High hit probability, combined with max damage from closely mounted parrallel guns. With reflector or ring and bead sights, and the attendant inaccuracy, I don't see wing guns as having any real disadvantages, only theoretical ones.

Anyways, I still vote for the Beaufighter. It's got the best of both worlds, awesome firepower from centrally located 20mms, and six brownings spread out on the wings to spread destruction (sic) over a wide area.

 

[Soren]

The Beaufighter lacks the destructive armament of other fighters though.

The Me-262 has the heaviest fighter armament featuring 4x 30mm cannons, while the Fw-190A-8/A-9 comes in as a close 2nd with 2x 13mm, 2x 20mm 2x 30mm cannons.

 

[Clay_Allison]

Hi Juha,

>Yes I know the FW 200 kills by Martlets/Wildcats but still the main adversarities of RN fighters were many time lone snoopers, so 6*.5s with fewer rpg made sense to it.

Just to make sure: If you had the choice of cannon, it never made sense to use the 12.7 mm Browning M2.

It always loaded your aircraft down more than any cannon battery, with all the inevitable negative consequences on performance and manoeuvrability this brings.

Here is the well-known comparison repeated for yet another aspect, equal ammunition capacity:

6x ,50 Browning M2 - 240 rpg, 18 s duration - 332 kg - 1,7 MW firepower - 31.4 MJ total supply
2x Hispano II - 150 rpg, 15 s duration - 174 kg - 2,1 MW firepower - 31.8 MJ total supply

It's amazing how often I can post facts and figures in this thread just to get the same old "but for XY, the fifties were good enough", with XY being everthing from "fighters", "Condors", "mounting it on a tank" or "mounting it on a ship". The only one that is missing is "using it as a boat's anchor", and that's almost the only honest assessment in a discussion of aircraft armament.

Regards,

Henning (HoHun)

The fifties were what we used because the US cannons sucked. For some reason the War Department didn't want to take British advice so we screwed around all war without them.

In retrospect, if it was me making the call in 1940, I'd neck up the .50 BMG case to 20mm and load HE rounds in a rebarrelled and lightened M2.

The result would have been much like the Japanese 20mm cannon in power. Less than many others, but light and very high damage/weight ratio. PETN weighs far less than lead.

Imagine a P-47 with 8 CANNON! That woud be incredible.