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German 15mm MG 151: Missing API shell


KillaKiwi
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# Game version

My game version: (2.11.0.92)

# Description

The gun is missing the Panzerbrandgranatpatrone o. Zerl. (Armorpiercing-incendiary non self-destructive = API) which is part of the reccomended ammunition composition from June 1944.

Velocity should be 960m/s according to German ballistic data.

Incendiary filling is the same as the 13mm API shell -> 0.86g Phosphorus

# Steps to reproduce the issue

  1. Compare available 15mm MG 151 ammunition in-game

# Affected vehicles

  • Do 335 A-0

  • Do 335 A-1

  • Possibly Bf 109 F-2 and F-4. Since this ammunition type was only introduced at a later timeframe (after mid 1943), the early aircrafts should technically not have them)

# Files

Spoiler

20211129205018_1.jpg.481e45f4206a6f09652

 

# Sources

Handbuch der Flugzeug Bordwaffenmunition 1936 - 1945

http://michaelhiske.de/Wehrmacht/Luft/HandbuchBordwaffenMunition/Deckbl.htm

-> 15mm API

http://michaelhiske.de/Wehrmacht/Luft/HandbuchBordwaffenMunition/Teil04/Blatt10.htm

 

15mm API Ballistics:

http://michaelhiske.de/Wehrmacht/Luft/HandbuchBordwaffenMunition/Teil01/Seite34.htm

Spoiler

obraz.png.73ab53c9df1da73384b69b19e6e709

960m/s muzzle velocity

 

Munitionsvorschrift für Fliegerbordwaffen Teil 10

-> Recommended Belt composition for 15mm MG 151, 1944:

https://archive.org/details/ldv400010munitionsvorschriftfuerfliegerbordwaffenteil101944/page/n27/mode/2up

IT, API

 

-> 13mm API

https://archive.org/details/ldv400010munitionsvorschriftfuerfliegerbordwaffenteil101944/page/n77/mode/2up

0.36g Phosphorus in incendiary capsule

 

Comparison 15mm API vs 13mm API. 1:1 Scale

Spoiler

Blatt10.jpg.ed39a8bf6ed8018db21fe229fdd2 Blatt08.jpg.7804fbed16b1bfbbbfa0b737a775

-> From the dimensions the 15mm API uses the same incendiary capsule as the 13mm API.

 

The German ammunition manual writes 0.36g but by measuring the cavity it's clear that there's enough room for twice or more phosphorous and that this figure must be wrong.

Depending on the density of the phosphorous, the bullet can hold between 0.7-0.9g.

It's therefore very likely that the actual filling was 0.86g and the 8 was read as 3 when it was copied to the manual.

 

Edited by KillaKiwi

blockhaj (Posted )

Moved to ask the experts due to lack of information requiring discussion and further research.
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Hello! Thank you for wanting to improve the game.

:salute:

 

To implement this projectile we need its muzzle velocity from said gun and the ammount of phosphor filler.

 

Ping this comment if you have a pending comment or if you update the OP.

Edited by blockhaj
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13 hours ago, blockhaj said:

Hello! Thank you for wanting to improve the game.

:salute:

 

To implement this projectile we need its muzzle velocity from said gun and the ammount of phosphor filler.

 

Ping this comment if you have a pending comment or if you update the OP.



Below velocties over distances. The projectile weight is 59 g, the muzzle velocity 960 m/s. The weight of phosphor filler is not given here, but for sure it's not less than what we have for 13 mm API in the game.
Gir5WjD.jpg

Edited by Ein79
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On 04/12/2021 at 00:44, blockhaj said:

Ping this comment if you have a pending comment or if you update the OP.

 

On 04/12/2021 at 00:44, blockhaj said:

To implement this projectile we need its muzzle velocity from said gun and the ammount of phosphor filler.

It's basically the same round as from this report:

 

The amount of Phosphor filler isn't known to me but could be estimated from the drawings.

 

 

 

 

 

Edited by KillaKiwi
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On 04/12/2021 at 00:44, blockhaj said:

Hello! Thank you for wanting to improve the game.

:salute:

 

To implement this projectile we need its muzzle velocity from said gun and the ammount of phosphor filler.

 

Ping this comment if you have a pending comment or if you update the OP.

 

Muzzle velocity is 960m/s according to Handbuch der Flugzeug Bordwaffenmunition 1936 - 1945.

Phosphor filler will take some creativity I guess, because I can't find it anywhere.

obraz.png.73ab53c9df1da73384b69b19e6e709

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On 03/12/2021 at 23:44, blockhaj said:

Hello! Thank you for wanting to improve the game.

:salute:

 

To implement this projectile we need its muzzle velocity from said gun and the ammount of phosphor filler.

 

Ping this comment if you have a pending comment or if you update the OP.

 

 

I got you bud, the source lists additional stats if you care to give it a gander :)

 

unknown.png

 

 

unknown.png

 

 

 

Source: https://c-okrug.ru/ognestrelnoe/vintovka-mg10.html

 

 

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Thanks for the posts. I will forward the issue when i get time.

@KillaKiwi can you compile the sources into the OP and make it easy to understand. Please put large images into spoilers. Post a comment when you are done and ping this message.
 

For other pending comments ping this message to notify me.

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On 08/12/2021 at 03:14, nathanclawfish said:

 

 

I got you bud, the source lists additional stats if you care to give it a gander :)

 

unknown.png

 

 

unknown.png

 

 

 

Source: https://c-okrug.ru/ognestrelnoe/vintovka-mg10.html

 

 

 

That's for the 20mm API round though. However by comparing the 15mm API to the 13mm API it's clear that they use the same incendiary capsule.

I added this to the OP.

Edited by KillaKiwi
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24 minutes ago, KillaKiwi said:

 

That's for the 20mm API round though. However by comparing the 15mm API to the 13mm API it's clear that they use the same incendiary capsule.

Good eye. :good:

Ping this post if u have a pending comment.

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16 hours ago, KillaKiwi said:

 

That's for the 20mm API round though. However by comparing the 15mm API to the 13mm API it's clear that they use the same incendiary capsule.

I added this to the OP.

My bad, the joys of posting something at 2 AM, though you are correct in the assumption they share a capsule, tbh i am pretty sure i own an example in my collection, just have to weigh it on the kitchen scales, and subtract the bullet weight as i assume the phosporus would have burnt down when it fired. 

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22 hours ago, blockhaj said:

Good eye. :good:

Ping this post if u have a pending comment.

 

According to Munitionsvorschrift Fuer Fliegerbordwaffen Serie D Blatt 19, 13mm AP-I has 0,36g Phosphorous. But this seems like a mistake. The thing is, the volume of the incendiary capsule would indicate around 0,86g or 0,96g rather than 0,36g, which would be 10 times less than 20mm API, and the incendiary capsule is sure as hell not 10 times smaller in a bullet that weights basically 1/3 of the 20mm one, which would indicate it generally has 3 times smaller volume overal. 

Phosphorous has density of 1,82g/cm^3 so it seems unlikely the incendiary capsule has volume of barely 1/5 of cm^3.

 

22 hours ago, KillaKiwi said:

 

That's for the 20mm API round though. However by comparing the 15mm API to the 13mm API it's clear that they use the same incendiary capsule.

I added this to the OP.

 

Edited by Loofah
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German boats LS 3, VS-8, and VS-10 also use MG 151/15, but their ammo is "API-T". 

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On 10/12/2021 at 22:47, Loofah said:

 

According to Munitionsvorschrift Fuer Fliegerbordwaffen Serie D Blatt 19, 13mm AP-I has 0,36g Phosphorous. But this seems like a mistake. The thing is, the volume of the incendiary capsule would indicate around 0,86g or 0,96g rather than 0,36g, which would be 10 times less than 20mm API, and the incendiary capsule is sure as hell not 10 times smaller in a bullet that weights basically 1/3 of the 20mm one, which would indicate it generally has 3 times smaller volume overal. 

Phosphorous has density of 1,82g/cm^3 so it seems unlikely the incendiary capsule has volume of barely 1/5 of cm^3.

 

 

Yes. I'm aware that the 0.36g doesn't seem to be correct and that these German manuals often contain errors. The 0.36g figure might have been come from the 3.6g of the 20mm API.

However there's no other figure and I'm not sure how exactly this should be handled.

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On 15/12/2021 at 01:56, KillaKiwi said:

Yes. I'm aware that the 0.36g doesn't seem to be correct and that these German manuals often contain errors. The 0.36g figure might have been come from the 3.6g of the 20mm API.

However there's no other figure and I'm not sure how exactly this should be handled.

I will move this to ask the experts and let you guys discuss and research this until finalized. Once all the infromation has been found i will move the report back and forward it. Moving it means i dont have to approve comments.

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On 15/12/2021 at 01:56, KillaKiwi said:

Yes. I'm aware that the 0.36g doesn't seem to be correct and that these German manuals often contain errors. The 0.36g figure might have been come from the 3.6g of the 20mm API.

However there's no other figure and I'm not sure how exactly this should be handled.

 

We know the dimensions, so IMO we should calculate the volume of this and 20mm API and see what values we get. 20mm API for reference, to see if the calculations are matching up with historical data. I'll ask my brother, an engineer, if he can do that, since the shape is too complex for my v. basic math education :)

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On 15/12/2021 at 01:56, KillaKiwi said:

Yes. I'm aware that the 0.36g doesn't seem to be correct and that these German manuals often contain errors. The 0.36g figure might have been come from the 3.6g of the 20mm API.

However there's no other figure and I'm not sure how exactly this should be handled.

 

On 18/12/2021 at 02:41, blockhaj said:

I will move this to ask the experts and let you guys discuss and research this until finalized. Once all the infromation has been found i will move the report back and forward it. Moving it means i dont have to approve comments.

 

 

My brother made a 3d model and calculated the volume of the incendiary filler based on the 13mm AP-I bullet. It's 449mm^3. Which means the 0,36g value simply can't be right. Outer 2 dimensions were taken from Munitionsvorschrift Für Fliegerbordwaffen and the rest calculated based on the drawing.

Here's a cross-section with dimensions he got (values are displayed as rounded to 0,1mm, also he made the filler pointed to make it simpler to calculate - no worthwhile difference in volume)

IMG-20211221-WA0004.jpg.cd7987192f5163b5

 

White Phosphorous density is 1,82g/cm^3. Lets subtract 15% due to not perfect filling, and any errors stemming from not knowing the dimensions perfectly (but I think if anything, the volume is on the low side, since the capsule wall thickness in his model is too high). We get 0,7g of filler, which is roughly twice as much as indicated in the document, and this is basically worst case scenario, the most likely value probably is somewhere around 0,8g, damn, even 0,86g would be possible and this would also explain the 0,36g error - someone wrote an 8 that was for whatever reason not fully closed and it looked like 3 to the guy who was responsible for documents.

 

Original drawing:

obraz.png.7232cb0bf7debf96131be65ede7cc8

 

 

Edited by Loofah
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3 hours ago, Loofah said:

0,8g, damn, even 0,86g would be possible and this would also explain the 0,36g error - someone wrote an 8 that was for whatever reason not fully closed and it looked like 3 to the guy who was responsible for documents.

Oh yeah. 0.86g seems like a good fit, especially since errors like this were quite common. Maybe by doing that calculation with the 20mm API as well, we could have a reference.

 

On a different note: Maybe you can have your brother look into the Italian 12.7mm HE as well :P

 

I think with this we can move the topic back to historical reports and let Gaijin decide. Since fire chance is hard-coded anyway. I don't think it will make a differnece, if it is 0.7g or 0.86g.

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57 minutes ago, KillaKiwi said:

Oh yeah. 0.86g seems like a good fit, especially since errors like this were quite common. Maybe by doing that calculation with the 20mm API as well, we could have a reference.

 

On a different note: Maybe you can have your brother look into the Italian 12.7mm HE as well :P

 

I think with this we can move the topic back to historical reports and let Gaijin decide. Since fire chance is hard-coded anyway. I don't think it will make a differnece, if it is 0.7g or 0.86g.

 

The amount of beer I'll have to buy him grows exponentialy :D

If he has too much time to spare, I'll ask him to calculate 12,7mm HE and 20mm AP-I too.

Anyway, we talked and he decided on the thicker walls "to be on the safe side".

So 0,86g is not only possible, but highly probable.

Edited by Loofah
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31 minutes ago, Loofah said:

Anyway, we talked and he decided on the thicker walls "to be on the safe side".

What do you mean with thicker walls?

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9 minutes ago, KillaKiwi said:

What do you mean with thicker walls?

 

The "incendiary capsule" has walls made of Aluminium, Copper and Magnesium alloy, and these are just a bit thicker in my brother's model than in the drawing, which may limit the volume of the capsule by a few %.

Edited by Loofah
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21 hours ago, Loofah said:

 

The "incendiary capsule" has walls made of Aluminium, Copper and Magnesium alloy, and these are just a bit thicker in my brother's model than in the drawing, which may limit the volume of the capsule by a few %.

Oh yeah, now I see.

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  • 3 weeks later...
On 21/12/2021 at 23:13, Loofah said:

Anyway, we talked and he decided on the thicker walls "to be on the safe side".

So 0,86g is not only possible, but highly probable.

Your brother used 5.3mm for the diamter of the cavity but check the 13mm AP-I drawing. It says 6mm.

Considering they are identical on the 15mm variant, 6mm instead of 5.3mm would increase the volume by 44% for around 60% of the projectile and a bit less for the sharp tipped end.

So probably around 30% increase, which means that instead of 0.7g we would have ~0.9g. Very close to 0.86g which seems to be most likely number, as you have pointed out.

 

With this, I would like to summon blockhaj to get his opinion on the matter of the topic being ready to be approved.

 

 

Edit: Oh wait. 6mm is the diamter of the cavity but the incendiary capsule takes away some of that. Forgot about that because I was looking at the AP-T bullet... :(

 

 

Edit2: I checked the drawing from Munitionsvorschrieft für Fliegerbordwaffen and I actually got around 5mm for the cavity within the incendiary capsule.

So the only thing that would change the amount of filling would be the density.

On 21/12/2021 at 19:08, Loofah said:

White Phosphorous density is 1,82g/cm^3.

This is the lowest density of any form of Phosphorous. So, if we knew that they used anything other than White Phosphorous the density would be higher and so would the weight of the filling.

 

Edit3:

It should be noted that early 20mm AP shells for the FlaK 30 and 38 used Phosphorous filling but that was later changed to explosive filler to self-detonate at range.

Both 20mm AP and 7.92mm AP with Phosphorous filling couldn't handle temperatures above 40°C so the 20mm API was replaced by the 20mm AP with self destruct mechanism while the 7.92m API was altered to a version that could handle higher temperatures.

My guess is that they changed the type of Phoshporus to one that wouldn't easily self-ignite when exposed to hot weather or sun light.

Since 13mm API was only introduced in late 1942 and it doesn't have any hazard warning, my guess is that it was safe to handle and used less reactive Phosphorous which probably had a higher density than white Phosphorous.

 

Edit4:

If we replace the white phosphorous with red phosphorous (1.82g/cm³ vs 2.27g/cm³(+-0.07)) we get around 0.86g instead of 0.7g.

 

Edited by KillaKiwi
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On 13/01/2022 at 13:55, KillaKiwi said:

Your brother used 5.3mm for the diamter of the cavity but check the 13mm AP-I drawing. It says 6mm.

Considering they are identical on the 15mm variant, 6mm instead of 5.3mm would increase the volume by 44% for around 60% of the projectile and a bit less for the sharp tipped end.

So probably around 30% increase, which means that instead of 0.7g we would have ~0.9g. Very close to 0.86g which seems to be most likely number, as you have pointed out.

 

With this, I would like to summon blockhaj to get his opinion on the matter of the topic being ready to be approved.

 

 

Edit: Oh wait. 6mm is the diamter of the cavity but the incendiary capsule takes away some of that. Forgot about that because I was looking at the AP-T bullet... :(

 

 

Edit2: I checked the drawing from Munitionsvorschrieft für Fliegerbordwaffen and I actually got around 5mm for the cavity within the incendiary capsule.

So the only thing that would change the amount of filling would be the density.

This is the lowest density of any form of Phosphorous. So, if we knew that they used anything other than White Phosphorous the density would be higher and so would the weight of the filling.

 

Edit3:

It should be noted that early 20mm AP shells for the FlaK 30 and 38 used Phosphorous filling but that was later changed to explosive filler to self-detonate at range.

Both 20mm AP and 7.92mm AP with Phosphorous filling couldn't handle temperatures above 40°C so the 20mm API was replaced by the 20mm AP with self destruct mechanism while the 7.92m API was altered to a version that could handle higher temperatures.

My guess is that they changed the type of Phoshporus to one that wouldn't easily self-ignite when exposed to hot weather or sun light.

Since 13mm API was only introduced in late 1942 and it doesn't have any hazard warning, my guess is that it was safe to handle and used less reactive Phosphorous which probably had a higher density than white Phosphorous.

 

Edit4:

If we replace the white phosphorous with red phosphorous (1.82g/cm³ vs 2.27g/cm³(+-0.07)) we get around 0.86g instead of 0.7g.

 

 

My brother, as mentioned, went with quite thick walls for the capsule, thicker than in the drawing so I'd trust that the diameter is at least as big as he got out of his software. I think any value between 5.3 and 5.65mm is realistic.

And I'd go with 0.86g filler anyway, since it's only value, other than 0,96g, you can write/copy poorly enough so it looks like 0,36, and 0,96g is a bit too much.

 

Edited by Loofah
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On 13/01/2022 at 13:55, KillaKiwi said:

With this, I would like to summon blockhaj to get his opinion on the matter of the topic being ready to be approved.

I have not followed the discussion but if yal have found sources etc and come to a valid conclusion then make a new report with all the proper information.

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52 minutes ago, blockhaj said:

I have not followed the discussion but if yal have found sources etc and come to a valid conclusion then make a new report with all the proper information.

Well, there is no source, that's why we used math to show that the only source that has a number is wrong :dntknw:

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