PDA

View Full Version : Let's not forget MG151/20 accuracy



Buzzsaw-
03-01-2005, 10:56 AM
Salute

With all the complaints about the MG151/20 explosive effectiveness, something seems to have once again been forgotten:

On average, the MG151/20's rounds had significantly LOWER muzzle velocity than the Hispano 20mm or the Soviet 20mm:

151/20

AP: 720 m/s
HEI: 720 m/s
HE(M): 800 m/s


Hispano Mk II

Muzzle velocity of API and HE ranged between 850 and 890 m/s.


Shvak

API: 750 m/s
HE: 790 m/s

Clearly, the MG151/20 rounds are going to suffer more bullet drop over a given distance, and the firing pilot will need to adjust his aim more to compensate for this drop.

To compound this disadvantage, there are THREE types of ammunition loaded in the MG151/20. All of these three different types had varying muzzle velocities and flight characteristics. The HE(M), which was the MG151/20 round with the highest muzzle velocity, was also the lightest at 92 grams compared to the 117 grams of the AP round and the 115 grams of the HEI round, and had the worst shape characteristics, which meant it was going to lose speed faster and suffer more bullet drop. It had initially a higher velocity, but decelerated the fastest.

All of these rounds were mismatched in terms of their flight characteristics and M/V.

Which meant that if a pilot aimed at a particular spot, one type of round might hit, but the next round in the belt would not because its M/V and shape were significantly different. Worse, the relationship between teh different rounds, the velocity and drop, were constantly changing during the course of their flight.

All this makes the weapon more difficult to use effectively in combat.

People raise the issue of the effectiveness of the MG151/20, without taking into account the fact that they are firing a mismatched set of rounds. They seem to expect that they will get a continuous stream of bullets, flying at exactly the same speed, and with the same bullet drop characteristics. Obviously wrong.

Compare that to the Hispano whose rounds initially have a much higher velocity, and which are closer in terms of their flight characteristics.

The same would apply to the Shvak, whose rounds have more similar flight characteristics.

The Hispano fires much heavier rounds, which are going to carry better.

Which brings us round to the obvious conclusion:

If you can't hit your target, you aren't going to do any damage.

The MG151/20 was significantly less accurate.


Above data taken from Tony William's site:

http://www.quarry.nildram.co.uk/index.htm

RedNeckerson
03-01-2005, 10:59 AM
I predict pwnage.

faustnik
03-01-2005, 11:03 AM
We had long discussions of this in previous Mg151 threads, the issue was not ignored. Were have you been Buzzsaw? http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

I'll try to link it for you.

Enofinu
03-01-2005, 11:07 AM
try dig something bad about .50cal machine guns Buzzaw, or something bad about P-51, or do u believe all that hype about em?? i bet you do. wasnt it you who claimed that tiger tanks were destroyed by ricoshedded ammo from below? http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

Atzebrueck
03-01-2005, 11:08 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Buzzsaw-:
With all the complaints about the MG151/20 explosive effectiveness, something seems to have once again been forgotten:
[..]
People raise the issue of the effectiveness of the MG151/20, without taking into account the fact that they are firing a mismatched set of rounds. They seem to expect that they will get a continuous stream of bullets, flying at exactly the same speed, and with the same bullet drop characteristics. Obviously wrong.
[..]
The MG151/20 was significantly less accurate.
<HR></BLOCKQUOTE>

In my opinion you are absolutely correct about the different trajectories of different types of ammunition.

But:
In the other threads, we are talking about the Mine shells missing from the belt http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif. So I would like you to see the thread on its own and not in relation to the "M-shell-discussion" http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif.

Anyway, at 50m the different bullet drop doesn't matter at all. And 20 hits are 20 hits, no matter how much bullets missed the target.
And IMO you shouldn't conclude that the MG151/20 was less accurate. Accuracy would be the dispersion you get, if you compare bursts of a single ammunition type.

Atzebrueck
03-01-2005, 11:09 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Enofinu:
try dig something bad about .50cal machine guns Buzzaw, or something bad about P-51, or do u believe all that hype about em?? i bet you do. wasnt it you who claimed that tiger tanks were destroyed by ricoshedded ammo from below? http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif <HR></BLOCKQUOTE>

Come on ... it's the third reply and you are about to start another flamethread ?! http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Buzzsaw-
03-01-2005, 11:16 AM
Salute Eno...

Do a search of the forums and you will find a thread in which I disputed the assertion that .50 cals could destroy Tiger tanks.

But you would probably be unlikely to do that, since it might prove your claim of bias to be completely bogus.

Charos
03-01-2005, 11:17 AM
Weapon accuracy between differing rounds has'nt been forgotten, but trying to test for the accuracy of these things is VERY difficult if not impossible.

We have no real gunnery range in IL2 in which to test, shore we know each round should drop X or Y meters fired from a horizontal gun but how do we test that in IL2?

Other than the Map grid data there is no way to get dimensional data for a bullets ballistics to see how many meters it drops over a given distance.

Hopefully our Friend BOB will asist us with these tools.

VW-IceFire
03-01-2005, 11:23 AM
I'm not going to miss with anything if my prop is chewing up his rudder http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

I can achieve some very good accuracy with the MG151/20...somtimes I can surprise myself and make what is essentially a perfect 50 degree deflection shot which results in a kill. Its rare but it can be done http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

I don't think this is an issue. The gun seems to behave like it was written when it comes to accuracy. Its just not belted properly.

Buzzsaw-
03-01-2005, 11:25 AM
Salute Charos

You can do a test for aircraft which have tricycle undercarriage. So for example, it is possible to test the MG151/20 (in He162) Mk 108. (in Me-262), Hispano (in P-400) and Shvak. (in B1)

You simply determine the starting position at takeoff of the aircraft on a dogfight airfield. Then you mark that with a large object at the side of the runway.

Then using the Full mission builder, you place objects at 100 meter intervals away from the aircraft's starting position. It is possible to do this since the smallest grid on the FMB is 100 meters.

Then you place cameras, and then start a record.

Then you fire the weapon and note where it explodes as it hits the ground, and measure the distance from the aircraft using your set of 100 meter markers. Then u calculate how high the muzzle is off the ground. (possible from data on height of aircraft) calulate the bullet drop for a particular distance from normal gravity equations, and you have your muzzle velocity.

I am too busy doing a Campaign for DCG now to have the time, but I would welcome others to do this. Personally I think muzzle velocity in game of Mk108 is too high.

Atzebrueck
03-01-2005, 11:29 AM
And how about using one of the "test-runways" or carriers where the plane position is locked ?

Still I'd recommend to rename the thread ... because nobody forgot about the accuracy.

As already mentioned the absolute ammount of hits or lack of mine-shells isn't affected by accuracy http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif.

faustnik
03-01-2005, 11:35 AM
I have not been able to get a good test of accuracy but, Mg151 should have very poor grouping at long range because of the factors that Buzzsaw mentioned. The gun should be firing three different types of rounds with three different weights at three different muzzle volocities. Effective range should be short (I have the LW charts somewhere, I'll find them) in the nature of 300 meters.

The sim does a good job in general of modeling relative 20mm bullet drop issues from what I have seen. The Hispano is by far the most accurate as it should be.

Charos
03-01-2005, 11:37 AM
I was doing something like you suggest recently with the HE162 Fireing off a carrier (Known Deck Height) that was parked off shore with markers every 100 meters.

I didnt get much further than that as I got side tracked onto something else but Im keen to go back and have another look.

But like I said before its not very accurate when you have ballistic tables with Drops in centimeters trying to relate that to the IL2 world without a virtual measureing tape isnt easy.

Buzzsaw-
03-01-2005, 11:40 AM
Salute Atz

You are correct, I forgot to mention you need to use the 'ship' runways.

And also the best place to do the test is on the MT map, which has very long sections of completely flat terrain on the coast.

Buzzsaw-
03-01-2005, 11:48 AM
Salute

Obviously you could not get exact measurements. But you could get a ratio of velocity and bullet drop between the different types of guns in the game.

The Mk108 should suffer very bad deceleration due to its overall large drag, and combined with its low muzzle velocity this should mean very quick bullet drop.

Same with Mk4 37mm U.S. gun.

BBB_Hyperion
03-01-2005, 11:49 AM
Well i doubt the testing method for the reason that shock absorbers are modeled on the wheels which spoils the flightpath of the bullets.

At least that was said for the testing method of the 50s dont see why it shouldnt apply in this case. So every test from Ground is inaccurate except without wheels maybe not tried ,)

Buzzsaw-
03-01-2005, 11:54 AM
Salute

Shock absorbers are modelled on ALL wheels, which means the ratio of effect from that would be the same.

Overall, you would only get a ratio between the different types of guns. But from that ratio you could tell if one was out of whack.

Anyway, it is too much time wasted for me to spend on it. I prefer to build my Malta Campaign... http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

faustnik
03-01-2005, 11:57 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Buzzsaw-:

The Mk108 should suffer very bad deceleration due to its overall large drag, and combined with its low muzzle velocity this should mean very quick bullet drop.

Same with Mk4 37mm U.S. gun. <HR></BLOCKQUOTE>

I agree with Buzzsaw on this one.

Except, the M4 fired a heavier shell at a higher velocity than the Mk108, it should have better single round accuracy, right?

Buzzsaw-
03-01-2005, 12:03 PM
Salute

Yes, the Mk4 37mm was slightly better than Mk 108, with 610 m/s compared to 505 m/s. But both are very poor compared to other weapons including Soviet 37mm which had a velocity of 900 m/s !!!!

Those people who complain about the Soviet 37mm being too good should look at the facts about this gun. (recoil is another issue... http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif )

The Mk 108 was designed to use against non-maneuvering targets like B-17's and B-24's in formation, not against maneuvering fighters.

It was a Potato gun at best.

Blutarski2004
03-01-2005, 12:54 PM
Anyone brave enough to venture into the archives can search for the official German 151/20 bullet drop data the was posted last year(?) by BB-Hyperion. Short story is that the 50cal was a considerably flatter shooting weapon than the 151/20. I do not recall which type of projectile was being used as the becnmark for the 151/20.

To those certain people who might get upset about this, please don't bother to flame me. I only deal in official data and that's what the numbers say.

faustnik
03-01-2005, 01:02 PM
Found it!

(Wait, better check where I got this. http://forums.ubi.com/images/smilies/1072.gif )

After 300 meters drop becomes a big factor.

p1ngu666
03-01-2005, 01:26 PM
ive wondered about volicty, anyway to reliably test?

test runway, object(s) a know or same distance apart, arcade 1, see the seporation

http://premium1.uploadit.org/pingu666//mg151test1.jpg

ull get something like that, thats 1000convergance, at a range unknow, chocked http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

WWMaxGunz
03-01-2005, 02:37 PM
Hyperion has data and drag formulae as well, he has been working on understanding drag
well enough to make close predictions.

All these things about varying trajectories for different guns was brought up years
ago. I know because I brought them up a few times while trying to explain possibilities
of some things.

If the range is not far, the deviation of rounds will be less than the size of your
target. It will also be vertical (up and down) deviation which will affect more firing
at wings from on edge than fuselages from any angle or wings from below or above.

ALL of this is part of the gunnery model and has been. Nothing new. And nothing to
do with explaining the ammo mix mix-up at all. Just smoke and maybe a mirror that
says "it's really this, not the ammo, it should be this way really, forget about it".