P-47 Movie (26 mb)

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RG_Lunatic said:
The MG131 13 mm rounds were so weak they'd have a hard time seriously hurting a P-47.
Click to expand...

Haha !!

Lunatic first of all the MG131 13mm rounds were fired at about the same velocity of the 7.92x57mm rounds ! They were very similar to the 50.cal's

Combining round weight and velocity, the kinetic energy from both calibers were about the same !

Where were you let to believe they were 'weak'

Are you sure your not mixing it up with the 20mm low velocity Mk108 cannon !

You seem to be 'very' fond of U.S. planes and equipment !

And yes the Bf109 would defidently turn inside the P-47 at high speeds !

The P-47's only real advantage in maneuverability, was its roll rate !
 

Soren - Lets look at the facts. Here are the figures for the .50 BMG, the MG131 13mm, MG151/20, and MK108:
Code: 
Gun Specifications
Weapon     Nation  Cart (mm)  Ammo Type  Prj Wt.(g)  MV (m/s) (g/mm2)  Mz. Power  RoF         Gun Wt.
--------------------------------------------------------------------------------------------------
.50 M2 BMG  USA    12.7x99     AP/Ball      48.6      870      0.383      1.0    750-850       30 kg
MG131 13mm  Ger    13 x 64B    HET          34        750      0.256      0.5    840(sync)     17 kg
MG 151/20   Ger    20 x 82     Mine         92        785      0.292      1.5    740/500(sync) 42 kg
MK 108      Ger    30 x 90RB   Mine        312        505      0.441      2.2    600           60 kg

Soren said:
Combining round weight and velocity, the kinetic energy from both calibers were about the same !

Where were you let to believe they were 'weak'
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There's no "belief" involved, the math does not lie. The MG131 13 mm round has half the kinetic energy of the .50 BMG - do the math yourself if you need convincing. The muzzel power figures given above are calculated for the KE of the round and then divided by the KE of the .50 BMG, giving a 1.0 value for the BMG and a value relative to the BMG round for all others (it's easier to relate them this way). Furthermore, the BMG round's velocity is actually that measured at 78 feet, where the MG131 velocity is at the muzzel, so the BMG muzzel power is actually understated (at the muzzel it's about 890 m/s).

The MG131 13mm also has only 75% of the sectional density of the BMG round, and it has much poorer ballistic shape. At 200 meters the MG131 has lost 23% of its velocity, where the BMG has lost only 10%, so the MG131 looses more than twice as much velocity as the BMG with distance. And for reference the MG151/20 looses 26.5% of its velocity in the first 200 meters.

As you can see, combining the round weight and velocity the BMG is far superior to the MG131! The MG131 was a very weak "heavy" machine gun. - QED

Soren said:
Are you sure your not mixing it up with the 20mm low velocity Mk108 cannon !
Click to expand...

Not at all. The MG151/20 had poor range performance because of its poor sectional density, poor ballistic shape, and medocre muzzel velocity.

Soren said:
You seem to be 'very' fond of U.S. planes and equipment !
Click to expand...

Some. In general, US fighters were much better than people here give them credit for. People here want to assume they engaged in the kind of combat favorable to their opponents, but generally speaking US planes controlled that aspect of the engagement and were able to dictate the nature of combat, which was based upon maintaining high speeds.

Soren said:
And yes the Bf109 would defidently turn inside the P-47 at high speeds !
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And what do you base this assertion on? The 109 lost turn performance with increasing speed, the P-47 did not. Also, the P-47 could roll while pulling G's with almost no loss of roll rate, the 109 could not do this (neither could the Spitfire, P-51, F4U, F6F, etc...).

Soren said:
The P-47's only real advantage in maneuverability, was its roll rate !
Click to expand...

That's not true, but at speed the difference in roll rate alone is enough to nullify any turn rate advantage the 109 might have had (but it didn't).

=S=

Lunatic
 
Guys, there is no doubt the P-47 is another one of the several great fighters of the war, but it was not perfect either.

Losses of P-47s in air combat with Bf109s and Fw190s were high RG.

USAAF veterans who naturally praise it like hell, have told me a dogfight with a Fw190 was an extremely close match, and the forecast on the outcome of the combat would rather be a withheld one. Some even used the word "fearsome" to describe the Butcher bird.

As to the Bf109 fighting the Thunderbolt, in some aspects the P-47 could surpass the 109 and viceversa. See the famous encounter of Gunther Rall who sent two P-47s down in quick succession flying his Bf109 just to get shot down himself after that, due to the overwhelming numbers of P-47s in the area.

Putting the level of pilot aside there (Gunther Rall) it is just one case that proves the P-47 and the Bf109 were both tough cookies.

RG, the allied historians have applied the term "outclassed" to describe the German planes indiscriminately totally losing the ground.


Now RG, let´s see this:

"In general, US fighters were much better than people here give them credit for."

Beg your pardon? It appears to me that statement applies not to the USA fighters but to the Germans!

As victors, naturally, they depict absolutely all allied fighters as superb flawless marvelous creations. On the other hand, the German fighters get little credit.

It has been the German fighters who have been defamed like hell by the bulk of the allied historians.

RG, try to answer this:

Just like allied literature puts it, the Bf109 began losing manouverability after the G-6 version...blah, blah, blah..."the model was starting to show its age". Didn´t a similar thing happened in the case of the Spitfire?

Do you think the Spitfire evolved from the MkI to the MkXIV, ending with the Mk21 version without losing some its original features?

The fuselage got redesigned, heavier in general, more powerful (heavier) undercarriages were fitted. The chances of a Mk21 against any German opponent, 109 or 190 A and/or D or Ta152 were not too promising.

Being issued with more powerful engines and with sets of more powerful weapons of course affected its handling.

It did!! And no one ever mentions anything on that.
 
First off all sorry i ment the MG-FFM not the Mk108.

Anyway Lunatic when comparing the KE of two rounds, then it is always a good idea to compare them with the same projectiles

You can't compare AP projectiles energy with an HET's for christs sake

The HET projectile is ment to blow an aircraft to pieces with Chemical Energy, while an AP round is ment to deliver High Kinetic Energy with a hardnened core inside, so it can penetrate the enemy Aircraft's armor by sheer KE !!

The 12.7mm 50.cal and the German 13mm round bear similar KE with AP projectiles. The 13mm AP projectile travels at over 800m/s while the less heavy 12.7mm round travels at 853m/s

Also the fact that the MG131 had a rate of fire of around 900rpm, is advantage in its own right ! And its HET rounds will cause some nasty surface damage if it hits an enemy plane ! If you for example hit one of the wings with a 5-7 of these, the plane will be very unmaneuverable and hard to control !
 
Sorry Soren, But actually it dont.

Here some ballistic tables. Velocity values for 13x64B API-T



Ballistic tables for HEI-T



The problem with this gun was the short cartrigde case.
 
Wait a minute !

Sorry my fault, i have apparantly mixed it up with the MG151/20!

I stand corrected.
 

Your data is just flat wrong. See this post on this board for the BMG data. As you will see the velocity of the 48.5 gram AP or Ball rounds is 2810 fps = 857 mps measured 78 feet from the muzzle. At the muzzle, this comes out as about 870 mps. The M1 incendiary round velocity is 2950 fps = 900 mps at 78 feet from the muzzle, which measures about 915 mps at the muzzle. The M8 API round velocity was 2910 fps = 887 mps at 78 feet, or about 900 mps at the muzzle. The WWII M8 round weighed about 44.5 grams, the M1 incendiary about 42 grams.

Then there is the issue of the actual German AP/I round performance (pure AP was not used). From Rheinmetall-Borsig - Maschinengewehr Mg 131/13mm tests (1943/44):

13mm Panzergranat Patrone L'spur El. o. Zerl. (AP/I Round)
Geschossgewicht (Projectile weight) 38.5g
Mündungsenergie (Muzzle energy) 975 m/kg
Anfangsgeschwindigkeit (Initial speed) 710 m/sec
time-to-distance (m/secs): 100m/0.151, 200m/0.325, 300m/0.523, 400m/0.748, 500m/1.004, 600m/1.292, etc...

As you can see the round is NOT heavier than the BMG rounds! And the velocity of 710 m/s is far less than the "over 800 m/sec" you quoted. If you do the math on it, I think you will find this round has very similer, but probalby lower muzzle energy than the HET round, since it is only 11% heavier, but is 8% slower, and velocity is squared in the KE calculation. However, it will hold it's velocity a little better because of its slightly better sectional density and tremendously better ballistic shape.

When I did my comparision tables (about 2+ years ago) I did not have data for the WWII M8 API round, so I had to use the AP/BALL round performance, but overall energy and performance will come out comprable to the AP/BALL rounds. The reason is simple - in the end the round must conform to the energy requirement of the gun. The projectile weight vs. the velocity must fit within fairly narrow parameters to operate the recoil or gas system.

So as you can see (I hope), the MG131/13mm was a very weak gun for its caliber. The reason is simple - it was an upgrade for 7.9 mm guns like the MG17 or MG81. It had to fit in the same space and mount on the same mounting points as those rifle caliber guns.

=S=

Lunatic
 
Lunatic didnt you see my previus post ?

I know i was wrong, i aparantly mixed up some data.

However the 50.cal had a normal velocity of 853m/s, and 890m/s for aircraft ammunition.

However i ca't see how you define the MG131 as weak !! It could easely rip holes in a P-47 and its 900rpm is also an advantage !
 
Even it cannot compare with the .50 "Ma deuce" wasnt a bad weapon.

His strong point was high rate of fire, 900 rpm is defensive enplacements. It drop slightly thanks to a neat electric primer to 840 rpm in sincronizated fire like FW-190 an BF-109.



The source of relative low velocity is his case wich have the same length that a .30 US Garand round.



Anyway the rate of fire and low recoil give it a concentrated cone of fire that could devastated a single engine plane. For example Erich Hartmann was a real fanatic of this gun, many times when he encounter a formation of russian bomber with escort, he engaged the fighters using only this heavy machine gun saving the Mauser cannon for sturdiers twin engined-Pe-2 and DB-3. In other ocasion he blasted away 3 P-39 Airacobras in matter of minutes using only MG-131 due his cannon was jammed.

A picture of the gun adapted for sincronized fire.

 
Yes the rate of fire was defidently an advantage And actually it was more like 930rpm !

Also the nose mounted low velocity 20mm MG-FFM could really do some serius surface damage !
 
Soren said:
Lunatic didnt you see my previus post ?
Click to expand...

I was editing my post, with several delays for phone calls, when CB and you posted. It is hard to get tables to line up in this editor.

Soren said:
I know i was wrong, i aparantly mixed up some data.
Click to expand...

NP, we all make goofs sometimes.

Soren said:
However the 50.cal had a normal velocity of 853m/s, and 890m/s for aircraft ammunition.
Click to expand...

Jeeze, I've given you the data strait out of the manual. And the manual is edited to peacetime specs, in wartime ammo was loaded hotter. The velocity of the .50, it depends on the ammo. Check the link to the other thread I gave for velocity info, and then factor in that these figures are taken at 78 feet and must be adjusted up to get an actual muzzle velocity. Then factor in that WWII ammo was loaded hotter than peacetime ammo. Normal quoted WWII figures are 870 m/s for the .50 AP/Ball round at 78 feet, and 880 m/s for the Hispano 20mm at 90 feet (Actually the ANM2 version of the Hispano II).

Soren said:
However i ca't see how you define the MG131 as weak !! It could easely rip holes in a P-47 and its 900rpm is also an advantage !
Click to expand...

Hmmm.... .50's fired at 800-850 rpm stock, 950-1050 if the "nickle trick" was used (very common for the P-51B and inner pair of guns on the P-51D), but this was not generally done on the P-47D. The P-47N on the other hand (at least the late models) had the .50 M3, and fired at 1200 rpm. The MG131/13mm fired at a maximum syncronized speed of 840 rpm, but this also could be lower depending upon engine rpm. Overall, 800 rpms for both guns are reasonable estimates, which means the P-47 has 4 x the volume of fire as compared to the MG131's of the 109K. Alternatively if you want to use maximums, the max rate of fire of the standard BMG is 850 rpms.

Now lets consider the kinetic energy of the rounds. At the muzzle, using the figures for the MG131 API vs. the M2 AP round (I have not run the ballistics for the M8 API, its a very involved process), we get:

M2 AP at 0 meters = 48.6 x 867 x 867 = 36532085.4
MG131 API at 0 meters = 38.5 x 710 x 710 = 19407850

M2 AP at 100 meters = 48.6 x 822 x 822 = 32838242.4
MG131 API at 100 meters = 38.5 x 619 x 619 = 14751698.5

M2 AP at 200 meters = 48.6 x 778 x 778 = 29416802.4
MG131 API at 200 meters = 38.5 x 539 x 539 = 11185058.5

M2 AP at 300 meters = 48.6 x 736 x 736 = 26326425.6
MG131 API at 300 meters = 38.5 x 472 x 472 = 8577184

So as you can see, at 0 meters the .50 AP has 88% more kinetic energy than the MG131 API. At 100 meters the advantage grows to 123%, at 200 meters to 163%, and at 300 meters it has grown to 207%. So in terms of kinetic energy, the .50 is more than double the power of the MG131 at 100 meters, and more than triple the power at 300 meters. And it just gets worse with increasing range.

The MG131/13 was a very weak HMG. It was about 2.5x more powerful than the 7.9mm guns it replaced, and had a little better ballistics too, but compared to other 12.7mm class HMG's it sucked! Why can't you accept this fact?

=S=

Lunatic
 
Soren said:
Yes the rate of fire was defidently an advantage And actually it was more like 930rpm !

Also the nose mounted low velocity 20mm MG-FFM could really do some serius surface damage !
Click to expand...

The MG-FF and MG-FFM were percussion primed and could not be synchronized, so they were never mounted in the nose. The MG151/20E was the syncronized 20mm gun. It fired at about 500 rpm when synchronized, about 750 rpm when free firing. The MG131/13 fired at 840 rpm maximuim when synchronized, but this was a maximum and depended on optimal and stable rpm, typical RoF was lower. Unsynchronized, I believe the MG131/13 could fire at something like 1050 rpm (relevant for bomber defensive gun installations)???

=S=

Lunatic
 
Lunatic those calculations of KE you provided are WAY off !!

Here's the correct KE amount:

MG131 AP at 710m/s= 9703.925 J

M2 AP at 867m/s= 18266.0426 J

MG131 HET at 750m/s= 10828.125 J

Also all the info i got on the 50.cal gives it a velocity 853m/s for landbased weapons and 870m/s for aircraft, and it aint peacetime ammunition

The Bf-109K-4 had the 20mm Mk108 in its nose (not the MG151/20), and its rounds were able to cause some serius surface damage if it hit an enemy plane !.
 
Soren said:
Lunatic those calculations of KE you provided are WAY off !!

Here's the correct KE amount:

MG131 AP at 710m/s= 9703.925 J

M2 AP at 867m/s= 18266.0426 J

MG131 HET at 750m/s= 10828.125 J
Click to expand...

Jeeze - I was giving the logic for relative power. The equation for ke is:

KE = 1/2 (mass x velocity squared)

Because it's a relative figure, we don't need to worry about 1/2, since it ballances for both sides. I suppose I should have worked it out fully to avoid confusion.

1/2 x 36532085.4 = 18266042.7, which is in grams. 1/1000 x 18266042.7 = 18266.042 which is in joules (i.e. kilograms) - and what do you know it matches your figure almost exactly!

I didn't give an terms of measure for the figures. They're in half grams newtons - LOL! The point is it doesn't matter what the terms are for relative values.

Anway, the math and logic is correct, the relative ke figures which were the point of the whole thing are correct!

Soren said:
Also all the info i got on the 50.cal gives it a velocity 853m/s for landbased weapons and 870m/s for aircraft, and it aint peacetime ammunition
Click to expand...

I'm not disputing those figures. I used 867 m/s for the AP round.

Soren said:
The Bf-109K-4 had the 20mm Mk108 in its nose (not the MG151/20), and its rounds were able to cause some serius surface damage if it hit an enemy plane !.
Click to expand...

I assume you meant to type 20mm. Yes I know this, but since that gun is virutally useless in a mutually aware dogfight what does it matter? "If it hit an enemy plane" is the operative phrase here. In a mutually aware high speed fight against a late model P-47 the chances of that are practically nil. The gun can't even be fired in a turn!

=S=

Lunatic
 
Because it's a relative figure, we don't need to worry about 1/2, since it ballances for both sides. I suppose I should have worked it out fully to avoid confusion.
Click to expand...

Its allright !


I assume you meant to type 20mm.
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No i meant 30mm !

Its alright as you said, anyone can goof up !
 

Ahh but there was no "goof". I never gave terms of the KE measures. The point was to show the relative hitting power advantage of the .50 BMG over the MG131/13, which was done correctly. The BMG is more than twice as powerful at 100 meters, and more than three times as powerful at 300 meters. This is why I say the MG131 was a very weak HMG.

=S=

Lunatic
 
That response was for you saying 20mm instead of 30mm So there you did goof up !

Anyway the MG131 wasnt a weak gun, because then it wouldnt have replaced the 7.9mm guns.

The 12.7x99mm 50.cal's were better yes, but in the end the size of the hole in the enemy aircraft would be 12.7mm with this round and 13mm with the other
 
Soren said:
Anyway the MG131 wasnt a weak gun, because then it wouldnt have replaced the 7.9mm guns.
Click to expand...

The 7.9 mm gun was a VERY weak gun! It has less than half the hitting power of the 13mm, and only about 1/5th the hitting power of the .50 BMG, and it looses energy even faster than the 13mm making it almost useless at 300m.

Soren said:
The 12.7x99mm 50.cal's were better yes, but in the end the size of the hole in the enemy aircraft would be 12.7mm with this round and 13mm with the other
Click to expand...

If it even penetrated, at any reasonable range (250m+) it was quite likely to just bounce off. After penetrating the skin of the target, it didn't have much energy left to do any real damage.

Was it better than the 7.9 mm? Most certainly. But it really fits better as a heavy LMG than to be classed with the true HMG's like the .50 BMG or Bresin UB 12.7mm.

=S=

Lunatic
 
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