Best armed fighter

[Soren]

The blunt shell would actually have basically little if anything, to do with the sectional density but it would have an impact on the Free Form which is about aerodynamics.
Interestingly its the Tracer that has a large impact on the aerodynamics, as it causes an increase in pressure at the rear of the shell where there is an area of low pressure. As the shell passes through the air it creates a vacuum effect behind the shell, which in turn sucks in the air that the shell is passing through. This causes turbulence (drag) and the drag reduces efficiency. By increasing the pressure the tracer reduces the amount of turbulence and reduces the drag. As you would expect streamlining has a similar effect.

Free Form ??? There's no such thing Glider.

Now if you were referring to the shape of the projectile then it's called the Form Factor, expressed as i mathematically. And depending on which i we're talking about, you also have to use different drag functions. (Either G1, 5, 6 or L)

 

[Burmese Bandit]

A note on projectile design and specifically on tracer improving trajectory effectiveness: this is seen in modern artillery shells. Modern 155 shells have a 'boat tail' to smooth airflow going around the back, combined with what to a layman would look like a slow-burning rocket at the back - the technical term is 'base bleed'. This indeed does increase pressure at the back, but it does not directly reduce turbulence - instead it pushes the area where the turbulence begins further back from the base of the shell. This reduces drag.

The effect, however, does not show much dividends at short ranges. A shell with this base bleed effect does not show much advantage over conventional shells in terms of speed retained at short distances. It is in the LONG distances that the advantages begin to manifest themselves, which is why base bleed shells have a 10-15% range advantage over other types of shells at their maximum ranges...of course, at the expense of a reduction in payload.

 

[kool kitty89]

Glider, I know there are advantages with the tracer (post #101), as I posted here a while back, I also didn't mean to imply that there would be a difference between the SD of the blunt shell to the streamlined one. (just pointing out that there was a substancial SD advantage)

I also posted earlier on the cannon armmed F-86 (post #100), but it seems to have been overlooked. In addition to the cannon armmed F-86K interceptor, there were operational trials of the 4x M39 armament on F-86E's and F's in Korea as well (project Gonval).
Cannon-Armed F-86Fs

Most significantly there was the F-86H with 4x M39 armament as standard. North American F-86H Sabre

 

[claidemore]

Free Form ??? There's no such thing Glider.

Check post #114 Soren. Glider called it Form Factor there, I believe it was just a 'slip of the tounge' when he used the term Free Form.


As for the Mk108, it's trajectory was dismal, to say the last. 330 gram projectile starting out at 500 m/s, it will have dropped 40 meters at 1000 meters. Nobody in the Luftwaffe considered it a long range weapon, just a very effective short range one.

 

[KrazyKraut]

I guess you asked every single one to be able to say that

On the HE machine gun rounds, there are a few reasons behind that statement (besides the "20 mm was determined to be the smallest caliber for a shell with worthwhile explosive capacity" statment -which is obviously debatable), The MG 131 HE round carried only 3.5% filler (1.2g) and the Italian-Vickers 12.7 mm even less at 2.2% (.73g) while the .50 BMG and .50 Vickers carry ~5% as pure incendiary rounds. ("de wild" derived)

That would imply that the particular incendiary machine gun rounds in question (esp. .50 BMG) simply carried more of the chemical agent than the explosive machine gun rounds of the opposite side and can thus be considered more effective, which makes sense.

However, I see no reason why incendiary rounds on heavy machine guns would be more effective than explosive rounds given all other variables being equal.

 

[kool kitty89]

I think it's just that the fuze took up so much space in such relatively small projectiles that the capacity of the rounds was very poor.
Of course, you could go without the fuze, but then you remove the delay, use a more sensitive explosive (possibly risking premature detonation) so only surface damage is done. (or the round fails to detonate) And there are other possibilities, like a high capacity projectile made of drawn steel. (though this would also give further advantage as an unfuzed/incendiary round) But this is getting outside the scope of this thread. (possibly deserving of its own)

The Italian 12.7mm HE rounds are a good example as the ammo was a semi-rimmed export version of the .5" Vickers (12.7x81), though the projectile was of Italian design. So a good comparison between the Italian HE round and the British Incendiary round can be made.

As mentioned before, the Italian HE round contained 2.2% filler. (with a mass of 33g and 0.73g HE)
The British Incendiary B Mark I.z (simplified "De Wilde") contained 5.3% filler (35.4 g and 1.94g HE)

The HE round can be seen below (far right): Untitled Document

And the Incendiary (right):

 

[HoHun]

Hi Koolkitty,

>I also posted earlier on the cannon armmed F-86 (post #100), but it seems to have been overlooked. In addition to the cannon armmed F-86K interceptor, there were operational trials of the 4x M39 armament on F-86E's and F's in Korea as well (project Gonval).

"GUNVAL", actually - as pointed out in the article you linked, it was a direct response to pilot complaints about the 12.7 mm guns lacking firepower.

On "GUNVAL" by one of the participating pilots (LtCol. George L. Jones, 335 FIS, from "MiG Alley" by Larry Davis"):

"In the winter of 1952-53, several F-86s were fitted with 20mm cannon in an attempt to increase the effectiviness of the F-86 in combat. The six .50 calibre machine guns of the F-86 Sabre did not have the hitting power needed for a quick kill. The mission for the day was to find and engage the MiGs and combat test the effectivess of the new guns."

Everyone trying to tell you that the USAF was satisfied with the 12.7 mm gun in Korea is obviously attempting to mislead you, or has not done his homework properly.

Regards,

Henning (HoHun)

 

[Glider]

Glider, I know there are advantages with the tracer (post #101), as I posted here a while back, I also didn't mean to imply that there would be a difference between the SD of the blunt shell to the streamlined one. (just pointing out that there was a substancial SD advantage)

I also posted earlier on the cannon armmed F-86 (post #100), but it seems to have been overlooked. In addition to the cannon armmed F-86K interceptor, there were operational trials of the 4x M39 armament on F-86E's and F's in Korea as well (project Gonval).
Cannon-Armed F-86Fs

Most significantly there was the F-86H with 4x M39 armament as standard. Cannon-Armed F-86Fs

I wasn't aware of the F86H being in such widespread use and I certainly didn't mean to overlook the posting.
Re the SD advantage it is substantial between the 0.50 and the 30mm but between the 20mm MkV and the 30mm its down to around 12%. This is a decent difference but nothing like the difference needed to make up for the difference in MV, where the 108 has around 2/3rds the MV of most 20mm guns.
Almost inevitably the SD tends to go to the larger weapon.

 

[HoHun]

Hi Claidemore,

>Nobody in the Luftwaffe considered it a long range weapon, just a very effective short range one.

Hm, what's your source for that?

A Luftwaffe study, published in Luftfahrt International 15 compares the low-velocity MK 108 battery installed in the Me 262 with a high-velocity battery consisting of 2 x MK 103 and 2 x MG 151 (15 mm) against Mosquito-sized jet bombers capable of a 750 km/h top speed, which the authors figured the Allies might field in the future.

The study concludes:

"When a gyroscopic gunsight (corresponding to the future standard equipment!) is used, the battery of 4 MK 108 is still superior even at large angles-off-tail. [emphasis original]

The MK 103 battery thus is not suited for conducting combat at longer ranges with better prospects. For gunnery against flying targets batteries of 4 MK 108 - even when combat against jet aircraft is considered - better than batteries of 2 MK 103 and 2 MG 151."

Here are the figures:

Combat range 800 m
Battery    Hits/s for angle-off-tail
Type       0 deg   15 deg   30 deg
2 MK 103:   0.24     0.22     0.17
2 MK 151:   0.39     0.36     0.27
4 MK 108:   0.49     0.45     0.29

As a large four-engined bomber flying at typical formation speeds was a much better target than a Mosquito-sized jet bomber, there should be little doubt that the MK 108 could successfully be used as an anti-bomber weapon at 800 m.

Figures for angle-off-tail 0, showing that the basic 1/r^2 range dependency of hit chances was not seriously affected by the MK 108's low muzzle velocity:

Battery    Fixed sight     Gyro sight 
Type       400 m   800 m   400 m   800 m
2 MK 103:   0.61    0.17    0.79    0.24
2 MK 151:   1.00    0.28    1.29    0.39
4 MK 108:   1.95    0.41    2.46    0.49

>As for the Mk108, it's trajectory was dismal, to say the last. 330 gram projectile starting out at 500 m/s, it will have dropped 40 meters at 1000 meters.

As you can see, it was still an effective weapon at 800 m, but I think your comment highlights one problem of our discussion: We have no clear definition what "long range" actually means.

Since Blesse suggests to get within 1200 ft when attacking MiGs, the RAF report shows that 86 % of all their kills were achieved at 400 yards and less, and the typical convergence ranges of WW2 fighters were in the 200 - 300 m range, I'd say that it makes sense to consider everything above 400 m "long range". I guess much of the disagreement in this thread is in fact due to unrealistic ideas on the feasibility of what I'd call extreme-range fire (beyond 800 m).

Regards,

Henning (HoHun)

 

[HoHun]

Hi Koolkitty,

>I think it's just that the fuze took up so much space in such relatively small projectiles that the capacity of the rounds was very poor.

Interesting consideration, thanks for pointing it out!

The HE round can be seen below (far right): Untitled Document

Hm, someone should tell Tony that the word of his site would be better spread if he actually entered a title tag for his pages

Regards,

Henning (HoHun)

 

[Juha]

Hello HoHun
Interesting info but if the results are per battery, then from the first table 2* MK 103 plus 2*MG 151 got in 30 deg scenario 0,17+0,27=0,44 hits per sec and 4*MK 108 got 0,29. So how was 4*MK 108 battery more effective in hitting, maybe by delivering more HE on target even with fewer hits? And how was the figures achieved, by calculations, I guess.

We know from real world that PR Mossies were difficult targets to Me 262s, they didn't were content with flying straight and level but tried by violently manoeuvring to throw off Me 262 pilot's aim.

Juha

 

[renrich]

I don't believe that anyone on this thread is claiming the US was satisfied with the armament of the F86. That misconception may be caused by a failure to thoroughly read posts or unfamiliarity with the English language. The facts are that the F86 was very successful against the Mig 15. 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. 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.

 

[KrazyKraut]

Certainly the Mosquito was a difficult target as it was very maneouverable and the Me 262 not so. I don't see that changing with a different armament though. Especially the MK 103 I would imagine as being far worse because of the much lower ROF.

 

[Burmese Bandit]

"...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..."

Renrich, AFAIK 'self destruct' means that the shells explode if they don't hit anything within a certain period of time. AFAIK the Germans added this feature to their shells so that shells which did not hit any target and falling out of the sky over germany would not explode in their own german towns and villages.

 

[Glider]

Hennings numbers are intresting but against a target trying to evade the fire the hit ratio would be much lower due to the time of flight.

However there is one point that springs to mind. The comparison was one aircraft with 4 x 30mm mk 108, the other 2 x 30mm mk103 and 2 x 15mm 151.

The sight on the aircraft with a standard battery would be configured against the 30mm Mk 108,
The sight on the other aircraft would have to be set against a compromise to allow for the different ballistics of each weapon. This is of course one of the problems of having mixed weapons, neither weapon will do as well as if they were on their own.

 

[KrazyKraut]

I don't believe that anyone on this thread is claiming the US was satisfied with the armament of the F86. That misconception may be caused by a failure to thoroughly read posts or unfamiliarity with the English language.

The F86's armament was lacking, the MiG's armament was overall better. That this fact is not clearly admitted but dodged by leading the argument astray and ad absurdum is what causes confusion. Not a lack of English or reading skills.

The facts are that the F-86 was very successful against the Mig 15. 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.

See, this is what I mean.

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.

Define poor. The MK 108's shells all had a very high sectional density, which alone should give them an acceptable BC. The 108's HE shells vary in terms of form factor, with the Ausf. C looking more streamlined than, for example, a 20x110 (HS.404) HE round. But that is debatable.

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 point is rather to improve penetration.

 

[renrich]

BB, Thanks for clarifying. I have wondered about the effect that the shells and bullets that missed must have had on the ground below.

 

[Soren]

Check post #114 Soren. Glider called it Form Factor there, I believe it was just a 'slip of the tounge' when he used the term Free Form.

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

As for the Mk108, it's trajectory was dismal, to say the last. 330 gram projectile starting out at 500 m/s, it will have dropped 40 meters at 1000 meters. Nobody in the Luftwaffe considered it a long range weapon, just a very effective short range one.

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.

 

[Soren]

A note on projectile design and specifically on tracer improving trajectory effectiveness: this is seen in modern artillery shells. Modern 155 shells have a 'boat tail' to smooth airflow going around the back, combined with what to a layman would look like a slow-burning rocket at the back - the technical term is 'base bleed'. This indeed does increase pressure at the back, but it does not directly reduce turbulence - instead it pushes the area where the turbulence begins further back from the base of the shell. This reduces drag.

The effect, however, does not show much dividends at short ranges. A shell with this base bleed effect does not show much advantage over conventional shells in terms of speed retained at short distances. It is in the LONG distances that the advantages begin to manifest themselves, which is why base bleed shells have a 10-15% range advantage over other types of shells at their maximum ranges...of course, at the expense of a reduction in payload.

Very true BB. That is why the Germans opted for heavy boat tailed projectiles as their std. rifle projectiles. The German sS projectile for example, which by late 44 was restricted for Snipers mostly, is even by todays standards an extremely slick stable projectile, easily outperforming the 7.62mm M118 M72 match round used as the std. Sniper rounds today. The BC of the 198gr sS projectile ranges from .557 to .584, compared to the .505 to .530 of the 173gr M72 and .480 to .507 of the 168gr M118.

As for tracers having reduced drag, well not regular tracer bullets, infact the loss in mass because of the phosphor burning away causes the SD to drop and with it the BC. Therefore tracer rounds usually have a shorter maximum range than the regular rounds.

 

[HoHun]

Hi Juha,

>Interesting info but if the results are per battery, then from the first table 2* MK 103 plus 2*MG 151 got in 30 deg scenario 0,17+0,27=0,44 hits per sec and 4*MK 108 got 0,29. So how was 4*MK 108 battery more effective in hitting, maybe by delivering more HE on target even with fewer hits?

Yes, the 30 mm hits were of course much more effective than the 15 mm hits, so the MK 108 came out on top.

>And how was the figures achieved, by calculations, I guess.

The fixed sight errors were based on data from cine-gun films, the gyro gunsight errors were based on the experiences of the Erprobungsstelle, the average tracking error was based on frontline film evaluation ("by Dr. Th. W. Schmidt" - perhaps this is a lead for further research), and the weapon dispersion (considered the least influential parameter) was based on the measured pattern of the Me 262 battery and on parameters based on the experience of the Erprobungsstelle Tarnewitz for the MK 103/MG 151 battery. Of course, you can't consolidate all of that data without some calculation, but the data is as realistic as it's going to get - and the Luftwaffe experts were genuinely interested in finding the best available armament option, not in bashing someone on the internet.

>We know from real world that PR Mossies were difficult targets to Me 262s, they didn't were content with flying straight and level but tried by violently manoeuvring to throw off Me 262 pilot's aim.

Absolutely ... an evading Mosquito would require closing to short range for realistic chances for a kill, and the Mosquito would still have the manoeuvrability advantage typical for propeller-driven aircraft there. However, the report I quoted considered fast jet bombers, and that would change the game a bit.

Regards,

Henning (HoHun)