Best armed fighter

[renrich]

Let us examine some ballistics numbers from the Nosler handloader manual. Compare two bullets-.308 cal. 180 grain spitzer with a sec. den. of .271 and a bal. coef. of .456 and the 180 gr protected point( which has a similar shape to the 30 mm projectiles except for the tungsten core one, in other words is blunt nosed) The PP bullet has a sec. den. of.271, and a bal. coef. of .355. Performance wise if both bullets start out at 2800 fps, the spitzer has a time of flight to a target at 500 yards of .6568 seconds and a bullet drop from the muzzle of 72.8 inches. The PP bullet respectively has a time of flight of .7002 seconds and drop from muzzle of 79.6 inches. Starting with a MV of 1800fps, the spitzer has a TOF of 1.0422 seconds and a bullet drop of 181.7 inches, whereas the PP has respectively 1.103 seconds and 199.2 inches. Obviously I don't have the ballistics for the 30 mm shells but one can see that the form factor has a big influence on the trajectory and time of flight.

 

[Glider]

Maybe, but it still strikes me as a very odd misspelling.

It was a mistype Soren. I have been working with a company called Free Form, these things happen

Sorry but that's just pure rubbish Claidemore. The Mk108 was considered a very effective weapon for long range shooting by the LW, one of the most accurate.

I take it that you can support this statement Soren.

If the 30mm Mk108 was considered such a good long ranged weapon, why did they try fitting a 50mm to it?
Also why did the Germans go to such trouble to fit the Mk103 into Fw190's?
Finally why did the Germans even think of putting higher velocity Mk 103 and Mk 151 15mm into the 262?

 

[Soren]

The answer is simple Glider: A shorter flighttime. The Mk103 would've made deflection shooting in dogfights easier. But that's not what we were discussing, we were discussing ballistics accuracy, and the Mk108 was one of the more accurate guns put on LW a/c.

Now to top it off you simply have no proof that the accuracy or ballistics of the 30mm Mk108 was bad. I on the other hand have the LW pilots opinion which makes it quite clear that the Mk108 was one of the most accurate guns.


HoHun has also presented a study from Luftfahrt 15 which shows the superior accuracy of the Mk108, even in deflection shooting. So what is your source for saying the opposite besides opinion?

 

[Glider]

The answer is simple Glider: A shorter flighttime. The Mk103 would've made deflection shooting in dogfights easier. But that's not what we were discussing, we were discussing ballistics accuracy, and the Mk108 was one of the more accurate guns put on LW a/c.

Trying a Mk103 in a dogfight is at a disadvantage due to the low rate of fire and the huge amount of extra weight which would also ruin performance.
Also the concept of trying a 50mm as a dogfighting weapon is unthinkable. Th only reason you would try a 50mm is if you wanted to fire at long range. Which if the 108 was so good at long range, would not be required.

Now to top it off you simply have no proof that the accuracy or ballistics of the 30mm Mk108 was bad. I on the other hand have the LW pilots opinion which makes it quite clear that the Mk108 was one of the most accurate guns.

Look at Hennings chart on posting 22. That shows you the poor balistics at any range.

Read the explanation in posting 28 for the reason for the dip.

HoHun has also presented a study from Luftfahrt 15 which shows the superior accuracy of the Mk108, even in deflection shooting. So what is your source for saying the opposite besides opinion?

Accuracy is one things, accuracy at range is another. The Mk 108 may well be accurate but I don't believe that it has range.

Now if I could ask you to supply the details of those pilots who believed the mk108 to be accurate at long range, I would appreciate it.

 

[Juha]

Hello HoHun

Thanks for the background info on the LW study. Much appreciated.

Quote:" the Luftwaffe experts were genuinely interested in finding the best available armament option…"

Of course that was/is the function of operational studies. But sometimes the studies of different nations got slightly different results. If you look Tony's Flying Guns WWII p. 41-42 You will notice that British conclusion after tests against British a/c was that "although German M-Geschoss contained more explosive, the powerful Hispano [with HEI] stood more chance of doing serious damage – such as the breaking of spar flanges – or of reaching the fuel tanks."

Tony's conclusion is that whether a Hispano HEI or 20mm M-Geschoss would do more damage depended on the a/c being attacked and exactly where the shell detonated.

Soren
if you study the tables in HoHun's message # 129, you will notice that in fact MK 103 was significantly more accurate in deflection shooting at 800m, if we definite accuracy as how high % of fired shells hit the target. At 30 deg deflection one MK 103 even got more hits per sec than one MK 108, even if 103 had much lower ROF. And even at 0 deg deflection the number of hits per sec was almost the same, 0,12 vs 0,1225 per sec and so MK 103, because it got its results with fewer shells, was more accurate. On the other hand MK 108 was clearly more efficient in that IIRC two MK 108 with ammo weighted more or less as much as one MK 103 with ammo, so one got clearly more hits per given weapon installation weight.

 

[HoHun]

Hi Juha,

>If you look Tony's Flying Guns WWII p. 41-42 You will notice that British conclusion after tests against British a/c was that "although German M-Geschoss contained more explosive, the powerful Hispano [with HEI] stood more chance of doing serious damage – such as the breaking of spar flanges – or of reaching the fuel tanks."

>Tony's conclusion is that whether a Hispano HEI or 20mm M-Geschoss would do more damage depended on the a/c being attacked and exactly where the shell detonated.

Hm, though I'm sure the British report on German weaponry was prepared with professional care too, the situation is a bit different than with German experts evaluating German weapons. The British did not have the full background on the Luftwaffe mine shell concept, which had been developed under consideration of just the points listed by Tony. Within its scope, the British report gave a correct answer, but the Germans had answered the additional question of how likely each type of hit was, and concluded that the mine shell was superior to other shells. This was the result of additional research unknown to the British experts, so there is really no fault in their analysis, it's just that it is not exhaustive to the subject.

Regards,

Henning (HoHun)

 

[Juha]

Hello HoHun

Quote:"This was the result of additional research unknown to the British experts, so there is really no fault in their analysis, it's just that it is not exhaustive to the subject."

Well, true, but on the other hand Germans didn't have access of the results of the British practical shooting tests either. British results and the reasons of Tony's conclusion seemed reasonable to me in light of what I learned and saw while serving as combat engineer. Over ½ of page 42 is on these differences between the effects of M-Geschoss and 20mm Hispano HEI. A bit same difference was between KM's 127mm and RN's 120mm shells and their fuzing. Seems that Germans had bit different approach to the question what was the most effective way to achieve the most destructive damage to the target than Brits.

Juha

 

[Soren]

Glider, you should read some of the LW after action reports.

As for bullet drop, the 30mm shells from the Mk108 dropped about 30m at 1,000m.



Now besides pure assumption, what is it that makes you claim that the Mk108 was inaccurate at range ? Do you have any specific proof Glider ?

 

[Glider]

Soren
I never questioned its accuracy, but I did question its range and it depends if you think a 31 meter drop is good but its an interesting chart. Where do you get them as I would be interested in getting some copies.
Re the after battle reports I am happy to read them if you can point me in the right direction.

 

[HoHun]

Hi Juha,

>Well, true, but on the other hand Germans didn't have access of the results of the British practical shooting tests either.

Well, the German experts didn't compare British rounds to Luftwaffe rounds, but rather conventional high-explosive rounds (similar but not identical to the Hispano's) to mine shells of the same calibre. They found these mine shells to be superior for air-to-air fire for all guns of 20 - 30 mm calibre, both low-velocity guns like the MG FF and high-velocity guns like the MK 103. I'm sure that had a mine shell existed for the Hispano cannon, it would have been found superior to the high-explosive shell too. What's more, the Germans - unlike the British - actually had extensive combat experience with all these types of guns, so that they could validate their findings. Even the Schießfiebel gunnery textbook took care to point out that the standard beltings (with high mine shell count) were 'well proven' ("bewährt").

The British based their conclusion on a rather slim data basis: "For comparison purposes a few rounds of 20 mm Hispano HEI was fired at the same target as above."

(One aspect not to forget is that the MG 151/20 had a 20% rate of fire advantage over the Hispano II, so that even with shells of equal destructiveness, it would still retain an advantage.)

>Over ½ of page 42 is on these differences between the effects of M-Geschoss and 20mm Hispano HEI.

Hm, except for the paragraph we already quoted, the left-hand column is mostly on 30 mm mine shells and their effects on Spitfire and Blenheim fuselages.

(Interesting in this context: I had been well aware of the popular "destroyed Spitfire" and "destroyed Blenheim" picture, but I had had no idea that the experiement had been repeated 10 times for the Spitfire and 11 times for the Blenheim. Score: 3 Spitfires immediately lethal, 7 Spitfires probably lethal. 3 Blenheims immediately lethal, 7 Blenheims probably lethal, 1 Blenheim doubtful.)

The right hand column has a description of Hispano effects on the target, followed by Tony's conclusion which you already quoted. The mine shell is only mentioned because produces smaller and lighter fragments than the Hispano shells, but as the "very-high-velocity, very small fragments" of the MK 108 mine shell had proven quite devestating in the US test against a B-24 fuselage, cutting control cables and fuselage longerons, I'd not consider that a disadvantage.

I don't think we can really conclude much more than we already did from that page - but maybe Tony is lurking and could provide more details for us?

Regards,

Henning (HoHun)

 

[kool kitty89]

Switching to 20 mm cannon was not however an unmixed blessing from a reliability point of view. One of my sources who operated the F8U mentioned that the care and feeding of it's 4-20mms was extremely complicated and not always successful.

The Crusader used the Colt Mk.12 cannon, a gun based on the Hispano, but with a rate of fire of ~1,000 rpm, it used ammunition similar to the USAF's used on the M39 and later M61 (derived from the WWII .60 cal ATR) but with a case lenthened from 102 to 110 mm and fired a heavier projectile at a slightly lower velocity. The reliability problems seem to have been resulted to the feed system as you mentioned, being particularly sensitive to high-G maneuvers (also a problem on the Pre-D P-51's .50's). I'm not sure how the reliability of the M3 (used just afer WWII and by the USN in Korea) or M24 Hispano would compare for reliability, but I expect they'd be better.

My source on the various German 30 mm shells has the MK 108(mine/tracer) with a MV of 1640 fps, and calls it self destructive. I assume that means it explodes upon contact. It is very blunt nosed, not spitzer shaped which would give it a poor BC. The Mk 108(incendiary) has a similar MV and is also self destructive and has the blunt nose. The MK 103(tungsten cabide core) has a MV of 3150 fps, is not self destructive but is meant for use against tanks. The projectile is spitzer shaped which would enhance BC. The Mk 103(incendiary/tracer) has a MV of 2950 fps, is not self destructive and has the blunt nose. It appears that all the rounds meant for air to air combat would have poor BCs and the two explosive rounds do not have a particularly high MV. In fact their MV is inferior to the MV of the Japanese Type 99 model 2 MK4 20mm cannon used in the A6M which had a MV of 1968 fps.

The velocity figure for the Type 99-2 apears to be a figure for the Type 99-1 (600 m/s or 1968 ft/s) while that of the Type 99-2 should be 750 m/s or 2460 ft/s. (note the Type 99-1 and -2 are licensed derivatives of the Oerlikon FFF and FFL respectively)


The "self destruct" was, as Burmese Bandit mentioned, is a HE shell that detonates automatically after a certain period to avoid shells falling to the ground over friendly territory.

There was also a more streamlined "Type N" minengeschoss (with tracer) as I mentioned earlier, also I mentioned a thread discussing this and a page with info on the MK 108's ammo:

http://www.ww2aircraft.net/forum/weapons-systems-tech/30mm-mine-shell-12821.html

Komet weapons: MK 108 cannon

 

[Juha]

Hello HoHun

Quote:" The British based their conclusion on a rather slim data basis: "For comparison purposes a few rounds of 20 mm Hispano HEI was fired at the same target as above.""

Now British had made numerous tests with different Hispano ammos, so they had pretty good info on effects of those, incl HEI, beforehand.

Quote:" (One aspect not to forget is that the MG 151/20 had a 20% rate of fire advantage over the Hispano II, so that even with shells of equal destructiveness, it would still retain an advantage.)"

Now Hisso V had the same ROF or a bit better than MG 151/20. But of course Mk V was a bit later cannon.

Also important in the text were the effects on Hisso's 20mm HEI on armour and whatever was behind it the effects of very near detonation on self-sealing fuel tank. As we know the self sealing worked better against numerous tiny holes than fewer bigger holes.

Juha

 

[HoHun]

Hi Juha,

>Now British had made numerous tests with different Hispano ammos, so they had pretty good info on effects of those, incl HEI, beforehand.

Hm, you have sort of a point there, but on the other hand, that they fired the extra Hispano rounds in the course of the mine shell comparison mentioned by Tony shows that they didn't actually have their data in a form that would have allowed a systematical analysis without extra firing trials, so I'd still consider they conclusion a bit shaky.

>Now Hisso V had the same ROF or a bit better than MG 151/20. But of course Mk V was a bit later cannon.

You're right, and it's just my assumption that they most likely tried it against a Hispano II projectile. The Hispano V had a better rate of fire, but the projectiles lost a bit of power due to the lower muzzle velocity, and as the late war MG 151/20 received the improved MX mine shell, it also increased its firepower.

The muzzle firepower data:

MG 151/20 (MX): 1,40 MW
MG 151/20: 1,27 MW
Hispano V: 1,23 MW
Hispano II: 1,06 MW

So the step up from the Hispano II to the Hispano V was about the same as that of the MG 151/20 with 3:5 mine shells to that with 3:5 MX shells.

>Also important in the text were the effects on Hisso's 20mm HEI on armour and whatever was behind it the effects of very near detonation on self-sealing fuel tank. As we know the self sealing worked better against numerous tiny holes than fewer bigger holes.

Roger, but if we're talking about an large number of very small, very-high-speed fragments that were capable of cutting fuselage longerons, I'm not sure that the result wouldn't be a big hole too.

However, the mine shell is primarily designed to attack the aircraft structure which makes up the greatest share of the target area, and damage against critical components, which make up a smaller share of the target area, is secondary. Armour piercing capability for example is zero, and this is accepted as there is only little armour on an aircraft, but large unarmoured areas that can be damaged very effectively by the maximized (for the respective calibre) blast effect of the mine shells.

An article in Luftfahrt International 7 describes blast damage experiments against aircraft components conducted in Tarnewitz, and the findings of those experiments describe the core idea of the mine shell concept:

"The mine shell ammunition for 2 cm and 3 cm projectiles increased the share of the completely destroyed surface in relation to the total surface to 60% for fighters and 30% for bombers."

So even if you have a projectile that does more damage against critical components than the mine shell, as long as the critical components make up less than 60% of the target area for fighters, and less than 30% of the target area for bombers, the mine shell will be more destructive overall.

The Luftwaffe squadrons could verify this easily by merely changing the belting order in their fighters as the traditional projectiles were still available to them and in common use (for example for use against ground targets), and as the hints in the Schießfiebel indicate, were not above a little experimenting to get the best effect from their guns. That the mine shell stayed the Luftwaffe's primary round for air-to-air combat simply shows that it was the best round for air-to-air combat - it had been selected in direct competition against traditional shells because of its merits in actual combat.

Regards,

Henning (HoHun)

 

[Kurfürst]

Also important in the text were the effects on Hisso's 20mm HEI on armour and whatever was behind it the effects of very near detonation on self-sealing fuel tank. As we know the self sealing worked better against numerous tiny holes than fewer bigger holes.

Juha

I think we miss the fact in this discussion that the MG 151 fired both high-capacity, thin walled M-Geschoss and the ordinary thick walled HE/HEI akin the Hispano's HEI round.

 

[claidemore]

I just think it is odd that even though the Luftwaffe considered that it took 25 to 35 hits from a 20mm cannon to down a 4 engine bomber, (which with the 'accurate' centrally mounted Mg151/20 is only a 2 - 3 second burst), they still felt it nescessary to add two more cannon with 'inaccurate' gondola wing mounts on the Me109.

This would indicate that combat experience showed that the accurate centrally mounted gun was not good enough, and that adding a couple wing guns with their corresponding convergence variance, increased hit probability and combat effectiveness.

 

[Juha]

Hello HoHun
all I would say that MG 151/20 and Hisso Mk V were almost as effective, which was better I cannot say and anyway in real combat the difference was probably meaningless. Much depended on circumstances, for average pilot MG 151/20 with M-Geschoss was probably better and also if one was attacking USAAF heavy bomber or B-26 Marauder; in case of a good shot attacking Blenheim or Ju 88, I maybe dare to say that Hisso would have been usually better because its ability to pierce armour, if one was aiming into cockpit and because of bigger fragments of its shell were more likely to make fatal damage to engine, if one was aiming engines. A good shot against fighter, now probably most fighters shot down were those whose pilots didn't see the attacker in time, so as above but if seen in time maybe M-Geschoss was better because against violently manoeuvring fighter the attacker would have been happy to got in some hits somewhere. Against Wellington Hisso would have been better and probably also against Il-2. These thoughs are only opinions, nothing more.

Hello Kurfürst
You are rignt, but because Hisso fired heavier shell with higher MV, its HEI probably was more effective.

Juha

 

[HoHun]

Hi Claidemore,

>I just think it is odd that even though the Luftwaffe considered that it took 25 to 35 hits from a 20mm cannon to down a 4 engine bomber, (which with the 'accurate' centrally mounted Mg151/20 is only a 2 - 3 second burst), they still felt it nescessary to add two more cannon with 'inaccurate' gondola wing mounts on the Me109.

You're assuming 100 % hit rate there I'm sure the Luftwaffe wouldn't have worried about extra guns if their pilots could shoot that accurate, but the hit rate figure they were realistically expecting was less than 10 % (9 % at a combat range of 500 m in one report, 5 % with no range specified in another.)

The report specifying the combat range of 500 m points out that for a 95% probability of a kill, the attacking fighter would have to fire 275 rounds. That would take 23 seconds ... not a good idea to hang around for so long in the sights of multiple tail gunners.

>This would indicate that combat experience showed that the accurate centrally mounted gun was not good enough, and that adding a couple wing guns with their corresponding convergence variance, increased hit probability and combat effectiveness.

For anti-bomber combat, certainly - I don't think anyone would disagree. I'd even say that the single 20 mm nose cannon was a bit on the weak side against fighters too, but before this opinion gets misunderstood, I'd like to point out that it was still a better setup than the P-51D's:

Me 109G-6: 1,8 MW
P-51D: 1,7 MW

(Not because of the neglegible 0.1 MW advantage, but because the cannon was centrally mounted and had no convergence issues.)

Regards,

Henning (HoHun)

 

[HoHun]

Hi Juha,

>all I would say that MG 151/20 and Hisso Mk V were almost as effective, which was better I cannot say and anyway in real combat the difference was probably meaningless.

Absolutely - and your conclusion does in fact agree closely with the total-energy-based evaluation:

2x MG 151/20 - 388 rpg, 32 s duration - 250 kg - 2,54 MW firepower - firepower per weight: 10,15 kW/kg
2x Hispano V - 337 rpg, 28 s duration - 250 kg - 2,47 MW firepower - firepower per weight: 9,88 kW/kg

(I had to add an extra digit of accuracy to show any firepower difference at all

Just for grins, here a 12.7 mm battery of the same weight for comparison:

4x ,50 Browning M2 - 305 rpg, 23 s duration - 250 kg - 1,1 MW firepower - firepower per weight: 4,5 kW/kg

>in case of a good shot attacking Blenheim or Ju 88, I maybe dare to say that Hisso would have been usually better because its ability to pierce armour, if one was aiming into cockpit and because of bigger fragments of its shell were more likely to make fatal damage to engine, if one was aiming engines.

It's always possible to design a scenario where the one gun is better than the other, and if you're able to aim at a specific part of the plane, that's an overkill situation anyhow. (I don't think that the armour of a Ju 88 was capable of stopping either 20 mm.) Aiming at a specific part of the plane is easier with a centreline-mounted gun is easier, by the way, so the synchronizable MG 151/20 has some advantage here, too.

>Against Wellington Hisso would have been better and probably also against Il-2. These thoughs are only opinions, nothing more.

I agree on the Wellington, it's quite clear that the special construction method was not as vulnerable against mine shells as stressed-skin aircraft. I also agree partially on the Il-2, as the Hispano ammunition would undoubtly be better at piercing the armour tub.

On the other hand, the Il-2 wings were just as vulnerable to mine shells as most, and the wooden wings of the early variants were highly vulnerable because wood responds with rapidly spreading cracks to blast damage that unlike shears in sheet metal consume very little energy as they propagate.

But now we're getting very specific

>You are rignt, but because Hisso fired heavier shell with higher MV, its HEI probably was more effective.

I agree, for a single Hispano II shell I've got 106 kJ according to Tony's data, while the MG 151/20 HET achieved just 50.3 kJ and the HEI 50.6 kJ.

The MG 151/20 really scores by higher rate of fire and the use of mine shells, which yield 142 kJ for the early version and 161 kJ for the MX version.

Regards,

Henning (HoHun)

 

[Kurfürst]

Hello Kurfürst
You are rignt, but because Hisso fired heavier shell with higher MV, its HEI probably was more effective.

Juha

Why...?

 

[claidemore]

Hi Henning,

You're assuming 100 % hit rate there I'm sure the Luftwaffe wouldn't have worried about extra guns if their pilots could shoot that accurate, but the hit rate figure they were realistically expecting was less than 10 % (9 % at a combat range of 500 m in one report, 5 % with no range specified in another.)

This is my argument in a nutshell. 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.

I think the graphs in post #65 can be used to show that quite clearly. Move the target plane around on the graph erratically, and smaller 'circle' of the nose mounted guns will be off target more often than the larger, and often twin 'circles' of the wing mounted guns. Admittedly with less damage than a concentrated centrally mounted multi gun installation, but a miss is a miss and any hit is better than a miss.

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.

I am presently working in sales, and there is an 80/20 rule that states that 20% of clients buy, so most sales people concentrate on the 20%. But it's the sales people that work on the 80% that excell.

With aerial combat, that means either more guns spread out over a wider area, or more accurate shooting (computerized sights).