MK 108 Shells too slow

[rel4y]

I know that, but someone in this thread says 30 m/s is gonna make a huuuge impact on trajectory, because of kinetic Energy! Yes you hear right, kinetic Energy is the key here! ;)

 

The difference for delta 40 m/s (500 vs 540 m/s) is 66 ms flight time at 400m.

 

twist rate is 630mm and barrel length is 545mm.

[Enduro14]

thanks for the stats!!

 

question on the twist rate, im more familiar with something like 1/10 1 twist for 10 inches or whatever factor what is it for the mk108, im not understanding twist rate is 630mm?

Edited January 11, 2017 by Enduro14

[rel4y]

Oh thats quite easy, its 1 complete turn in 630mm. 630mm is 24,8 inches, so you get 1/24,8 inches twist. :)

[amazingme]

the actual barrel length of the weapon and then the twist rate, this weapon really reminds me of our mk-19 in a way. Very low velocity and your basically lobbing rounds in on tgt so its intriguing to me that their was a downward compensation in the barrel in the ME/BF-109. But then again maybe it makes sense since the aoa at altitude and engaging high altitude bombers makes sense???

 

so if you look at this http://www.luft46.com/images/mk108-3.gif

 

look at the side view left, from the tip of the round in chamber need the length from that tip to end of barrel. Im assuming it has to have some sort of barrel twists also..

 

so is 23 inch barrel correct? Via the Lua's does it annotate anywhere this sort of specifications? 23 inch barrel is what i have found for the real world mk108 have not seen anything in reference to rifling/twist rate

 

From the picture:

Barrel length is 1057mm - 672.5mm = 384.5mm

[DefaultFace]

So am I missing something or don't the values in the lua correspond exactly with the ones from the Schußtafel? Obviously if the Brandgranatenpatrone is actually Minenbrandgranatpatrone then that would be incorrect. Which round is supposed to have a v0 of 540m/s?

 

Side note rel4y do you have a Scußtafel for the M-Brandgranatpatrone? I can only find tables for the other 2 rounds.

[Enduro14]

Oh thats quite easy, its 1 complete turn in 630mm. 630mm is 24,8 inches, so you get 1/24,8 inches twist. :)

 

Ok thank you, so that is another reason for the round being less effective at range.

 

so this thread seems to somewhat answer what we are all looking at? As Rel4y provided great details and an answer from Yo-Yo

 

https://forums.eagle.ru/showthread.php?p=2843185

 

So with that my questions i personally have are this

 

1. is environmental factors incorporated in the ballistics in DCS?

 

2. What was the real world ttp in using the sight in the 109 with the mk-108 aka proper mil hold?

Edited January 11, 2017 by Enduro14

[rel4y]

Ok thank you, so that is another reason for the round being less effective at range.

 

Yes.

 

From the picture:

Barrel length is 1057mm - 672.5mm = 384.5mm

 

This manufacturer document disagrees with you.

 

http://www.deutscheluftwaffe.com/archiv/Dokumente/ABC/m/MK%20108/Text/Munition/Munitionentwicklung/Entwicklung%20Mu%20MK%20108.pdf

 

So am I missing something or don't the values in the lua correspond exactly with the ones from the Schußtafel? Obviously if the Brandgranatenpatrone is actually Minenbrandgranatpatrone then that would be incorrect. Which round is supposed to have a v0 of 540m/s?

 

Side note rel4y do you have a Scußtafel for the M-Brandgranatpatrone? I can only find tables for the other 2 rounds.

 

The op stated it should be 20-40 m/s faster. I dont know based on which source, but I just used 40 m/s as a demonstration. The values of the Lua are perfect in my eyes, for the M-Geschoss (330g) and M-Brandgranatpatrone (370g). So thats why I dont get all the fuzz. This table is for the M-Brandgranatpatrone (370g). It is mislabled as well, thats why in my bug report I suspected thats where EDs mistake comes from. To prove my point I posted the technical drawings of the shells which sho the correct weights and names.

 

[razo+r]

The thing is, i looked at the tables of the MK108 canon, not at shells, that's why i assumed it's too slow

[DefaultFace]

Ok. Now that you mention it I think we discussed in another thread that the table was mislabeled as well, seems I had forgotten.

 

S!

[DefaultFace]

razo+r nope, there is another table for the normal Minengeschosspatrone which has 500 m/s v0.

 

Both rounds fit the info in the tables.

 

Edited January 11, 2017 by DefaultFace
Added table

[razo+r]

yep, i mixed the leuchtspur with the non- Leuchtspur up

[razo+r]

I was thinking, with the muzzle velocity of the MK 108 labelled at 505-540 m/s, then that would apply to all shells, but apparently not

 

just one thing is a bit meh, that i haven't seen any other documents about the velocity of the shells except the ones posted here...

[rel4y]

So with that my questions i personally have are this

 

1. is environmental factors incorporated in the ballistics in DCS?

 

2. What was the real world ttp in using the sight in the 109 with the mk-108 aka proper mil hold?

Hehe, now were getting to the interesting things. ;)

 

1. Wind certainly is, but the rest as I said, no clue.

 

2. Look below at the graph. I also have the corresponding table here and REVI height is 74,5 cm over the MK 108 barrel line.

 

 

Edit: Graph reuploaded.

Edited January 11, 2017 by rel4y

[DefaultFace]

Don't think there is anything as far as proper mil hold but there is this:

 

http://rafiger.de/Homepage/Literatur/Schiessfibel.pdf

 

The table in here is fairly simplified and only valid for a certain round at a certain speed etc etc. Basically its a very rough guide. However it is worth reading, important part is understanding that lead needs to be varied depending on the difference in direction of travel between yourself and your target. Try to get a feel for what angle corresponds to what distance from the middle of the sight. Having a mental picture of an aircraft at 30° and knowing that means xyz radii from the middle of the sight. Eventually you'll just look at the airplane and know the distance needed. Takes alot of practice though.

 

Here is the USAF version of that document. see page 23-25 for some nice drawings on the topic of lead angle.

http://memory.loc.gov/service/gdc/scd0001/2010/2010_01/20100404008fi/20100404008fi.pdf

 

Edit: rel4y that link doesn't work, or at least not for me...

[amazingme]

Ok thank you, so that is another reason for the round being less effective at range.

 

so this thread seems to somewhat answer what we are all looking at? As Rel4y provided great details and an answer from Yo-Yo

 

https://forums.eagle.ru/showthread.php?p=2843185

 

So with that my questions i personally have are this

 

1. is environmental factors incorporated in the ballistics in DCS?

 

2. What was the real world ttp in using the sight in the 109 with the mk-108 aka proper mil hold?

 

I checked Yo-Yo's answer in the thread mentioned above. Are the ballistics implemented yet or are still in development?

[Enduro14]

I checked Yo-Yo's answer in the thread mentioned above. Are the ballistics implemented yet or are still in development?

 

that is the million dollar question, i would assume it will be imported along with the new damage model????

 

LOL that schiessfibel.pdf is quite hilarious much better than modern military manuals....

Edited January 11, 2017 by Enduro14

[rel4y]

Sure the ballistics are implemented. Thats why they corrospond to the charts! The K4 is not the first model with guns. This is probably modeled since some Flanker game 10 years ago.

[DefaultFace]

I think he meant corrected ballistics as per the change in rounds. To which I believe the answer is that depends....

 

As I understand the round is a M-Brandgranatpatrone, which is correctly modeled, ballistics wise anyway, just not labeled properly. So yes.

 

If the question is has the normal Brandgranatpatrone been modeled and or the belting been changed? Then no.

 

On yet another side note, I wonder if the round we have doesn't have the ballistics of a M-Brandgranatpatrone but the damage of a Brandgranatpatrone, since the 2 rounds do seem to have quite different effects in the sim. Would have thought that the M-Brandgranatpatrone and the Minengeschosspatrone have a fairly similar effect.

[funkyfranky]

The difference for delta 40 m/s (500 vs 540 m/s) is 66 ms flight time at 400m.

I don't think quoting absolute numbers is very intuitive in this case. The difference in velocity (or time) is 8%. To me everything >5% is not negligible at first sight. But everyone can make up his/her own mind on this.

I know that, but someone in this thread says 30 m/s is gonna make a huuuge impact on trajectory, because of kinetic Energy! Yes you hear right, kinetic Energy is the key here! ;)

Right, it is rather v_0 than E_kin, which is important for the trajectory. However, E_kin could be important for the (new) damage model. Hence, for the damage model the difference in E_kin would be >16%. That should be addressed, if the v_0 numbers are really off by that margin. Are they or are they not?

[DefaultFace]

Kinetic energy isn't really the deciding factor with damage caused by an explosive round.

[rel4y]

At 400m the Ekin at delta 40 m/s will vary by about 14% but in terminal ballistics the impulse would be much more important so that the exponential influence of v would be diminished. For a pure explosive shell it honestly doesnt matter much at all. Almost 100% of the effect will be chemical. But else I agree about everything you said.

Edited January 11, 2017 by rel4y

[amazingme]

Did you guys find another source beside http://www.eeoda.de/2008/0804_FB1_MunMK108.pdf related to the shells characteristics?

 

Kinetic energy is related to the velocity which is related to the distance of travel of the shell.

 

When I shoot with the MK 108 I shoot way within 100m from the target and 20 m/s means a lot when you have to land 1 M-Brandgranatpatrone or 2 or 3 on the target, from 50m, pulling 4 Gs... Does this make any sense to you or I'm being way off?

[DefaultFace]

Amazing, here is the source that rel4y and myself have been using over the last few pages.

 

http://www.deutscheluftwaffe.com/archiv/Dokumente/ABC/m/Munition/handbuchderflugzeugbordwaffenmunition1936-1945.pdf

[funkyfranky]

[...] in terminal ballistics the impulse would be much more important [...]

Why is the impulse (hence velocity) more important than the energy in what you call "terminal ballistics"? (serious question!)

[...] so that the exponential influence of v would be diminished. [...]

Because I keep hearing about an exponential dependence on v. That means you have a term exp(v) in the equation. This is rarely the case in physics (just think of the dimension exp(m/s)...). For example, E_kin~v^2 is a quadratic dependence :smartass:

For a pure explosive shell it honestly doesnt matter much at all. Almost 100% of the effect will be chemical.

Okay, that sounds very reasonable. Never mind my remarks regarding the damage model then :)

[rel4y]

@amazing: First of all I am sorry for being a bit of a dick to you in the first place. But you gotta admit as well that you provoked that... So lets get this crap settled, OK?

 

Hey funkyfranky! You are right, obviously v is not the exponent. The exponent is 2, which makes it a quadratic dependency. Valid criticism!

 

When saying impulse is more important I mean that the mass is "more important" in terms of deformation/damage to structure than the velocity, or lets say velocity is not "quadratically relevant". At least when looking at solid body impact and not plasma. This is especially true for armor penetration. So basically when assessing damage you would get a better picture by comparing the absolutes of the impulse instead of looking at kinetic energy. Thats empirically based though and obviously doesnt give the whole picture. Shape, material properties being a big player. This is only valid as a thumb guide for the same projectile shapes at different velocities/masses.

 

While having the same kinetic energy a heavier projectile will generally conserve its energy better and do more damage than a lighter, faster one.

 

I hope Im making sense.

Edited January 12, 2017 by rel4y