MG151 15mm vs 20mm

[-=PHX=-SuperEtendard]

11 hours ago, II./SG.1-MarkWilhelmsson said:

 

I have recently read that the MG151/15 either used a hardened steel penetrator or a tungsten penetrator in it's AP projectiles. The steel had somewhere around 28-30mm of penetration capability but the tungsten core projectiles could penetrate plate up to 48mm. All of this at 100m distance. If this is truth, then the MG151/15 should be compatible for use against even medium tanks like the T34. I am definitely going to do much more research on this matter and report my findings to the development department. Any source info anyone may have would be great!

It would be kinda hard to pen the T-34 I guess, at least from the side, even if the pentration at point blank range is over 40mm, you would have to consider the impact angle and the distance. Another important factor although not modelled in most sims I think is the steel hardness. The T-34's armor plates were of high hardness, which had it's pros and cons, it increased it's resistance against weapons with a lower caliber than the armor itself (37mm and lower) but it decreased it's effectiveness against higher caliber weapons (75mm and larger) it also made the armor more brittle so when getting hit by these large caliber weapons it was prone to spalling and send fragments of it's own towards the crew.

Edited May 5, 2020 by -=PHX=-SuperEtendard

[Jaws2002]

On 4/22/2020 at 9:36 AM, II./SG.1-MarkWilhelmsson said:

An example of this would be the fact that a 55gr 5.56 projectile at 3300fps will cut clear through an AR500 plate while the same plate will stop multiple hits from 150gr 7.62 at 2800fps with ease.

 

 

 

You are correct in general, but it's a bit more complicated than that. For armor penetration you want, high sectional density, and want your energy applied to as small area as possible. That's why all this modern tanks shoot 23mm-25mm diameter, almost a meter long rods, out of  120mm-125mm cannons.

Then the round construction and material also plays a big role.

 

But if i remember corestly, the 15mm AP was superior to the 20mm AP from MG151.

 

I had a PDF with the armor penetration values somewhere, but i couldn't find it. I did find the MG-151 maintenance manual and here's the table with the velocity and bullet weight difference.

 

 

 

 

 

EDIT: i found it. 

The 15mm is way better at defeating armor.

 

 

 

 

Edited May 7, 2020 by Jaws2002

[II./SG.1-MarkWilhelmsson]

1 hour ago, Jaws2002 said:

 

 

You are correct in general, but it's a bit more complicated than that. For armor penetration you want, high sectional density, and want your energy applied to as small area as possible. That's why all this modern tanks shoot 23mm-25mm diameter, almost a meter long rods, out of  120mm-125mm cannons.

Then the round construction and material also plays a big role.

 

But if i remember corestly, the 15mm AP was superior to the 20mm AP from MG151.

 

I had a PDF with the armor penetration values somewhere, but i couldn't find it. I did find the MG-151 maintenance manual and here's the table with the velocity and bullet weight difference.

 

 

 

 

 

EDIT: i found it. 

The 15mm is way better at defeating armor.

 

 

 

 

 

I mentioned sectional density in the exact post that you quoted from.

 

Thanks for these images; I'm compiling as much data as I can.

[Jaws2002]

1 hour ago, II./SG.1-MarkWilhelmsson said:

 

I mentioned sectional density in the exact post that you quoted from.

 

Thanks for these images; I'm compiling as much data as I can.

 

 

Sorry. I was doing few things at the same time when i was reading your post.

 

Here are the two documents this images are from.

 

First is the MG151 and Mg151/20 manual:

http://www.mediafire.com/file/1nnn7ktrg8x9v43/german_mg151.pdf/file

 

 And the second one is a US army technical manual about German cannon shells. Pretty interesting reading.

 

http://www.mediafire.com/file/bgtno3qsuf4hrvo/ADA376695.pdf/file

Edited May 7, 2020 by Jaws2002

[the_emperor]

10 hours ago, Jaws2002 said:

I had a PDF with the armor penetration values somewhere, but i couldn't find it. I did find the MG-151 maintenance manual and here's the table with the velocity and bullet weight difference.

 

[FTC_Zero]

On 4/22/2020 at 2:45 PM, RedKestrel said:

Even if the 15mm is faster the 20mm likely has equivalent kinetic energy due to the increased size of the round, and I would expect a 20mm AP round to still be better penetrating than a 15 mm.

With the new damage model you definitely want the high explosive if you have a choice, with the new modeling of aircraft skin and structure damage HE is more likely to produce critical damage no matter where you hit, whereas AP you need to hit pilot or engine. I don't think AP is really any better than HE at pilot kills either since the  pilot physiology update, since nearby HE explosions wound you or knock you out. 

After reading the dev blog about the new DM, it seems to me that chemical rounds are now more in favour compared to purely kinetic, do i understand that correctly? So imo 20 mm sould be better with minengeschosse but also without the DM update 20mm shuld be better because of the higher bullet mass. (I think penetration in air to air combat do not really matter, but the translated energy which was the main damage source if i understood correctly)
 

So in that regard some might like 15mm version feel better because of easier aiming, meaning, less leading.

3 hours ago, the_emperor said:

 

 

Spoiler

 

 

 

Is there also information in this manual how much 15mm and 20mm AP- bullets weight? We can simply calculate the energy with the velocity   f=v * m.

 

Side note: in fig.1 there is written: "Nur für den direkten beschuss von Panzern!" Meaning: for fighting tanks directly only. 

Edited May 7, 2020 by ZeroCrack01

[Yogiflight]

24 minutes ago, ZeroCrack01 said:

Side note: in fig.1 there is written: "Nur für den directen beschuss von Panzern!" Meaning: for fighting tanks directly only.

I don't know if this is meant, as I don't know if this is simulated in the game, but armor piercing rounds lose a lot of armor piercing effectivity, when they first have to penetrate, like you usually have it, when shooting at aircrafts, any other material, before hittng the armor plate. For example the thin aluminum surface of the aircrafts, penetrated at a very shallow angle, when shooting from behind, will make your AP round start tumbling, which reduces the armor piercing effectivity quite noticable.

[FTC_Zero]

36 minutes ago, Yogiflight said:

I don't know if this is meant, as I don't know if this is simulated in the game, but armor piercing rounds lose a lot of armor piercing effectivity, when they first have to penetrate, like you usually have it, when shooting at aircrafts, any other material, before hittng the armor plate. For example the thin aluminum surface of the aircrafts, penetrated at a very shallow angle, when shooting from behind, will make your AP round start tumbling, which reduces the armor piercing effectivity quite noticable.

This sentence means that you should use that kind of ammo only against battle tanks. That AP round has rare tungsten core and have specialised use. That 'directly' term seems missleading. At least that is what I would interpret with German as first language.

 

But if you are right about your thesis, then that would make the 20 mm by far the superior weapon, relying mainly on HE with insane amount of filler compared to other HE rounds. Damaging the plane by fragements and big holes, instead of hitting vitals parts inside the skin. I mean, new DM makes planes literally and far more commonly explode with those rounds. DAKA DAKA

[the_emperor]

1 hour ago, ZeroCrack01 said:

This sentence means that you should use that kind of ammo only against battle tanks. That AP round has rare tungsten core and have specialised use. That 'directly' term seems missleading. At least that is what I would interpret with German as first language.

 

[FTC_Zero]

49 minutes ago, the_emperor said:

 

 

Spoiler

 

 

What do we have here: 15mm HVAP round with total weight of ~55g

Other source up show 15mm HVAP round with ~52g

Let's take the average of 54g for the calculation:
(0.054 g *  (1030 m/s)^2)/2 = 28.6443 Joules

 

BUT also 15mm API round with 72g weight (AP round for air combat belts, as we know now, the HVAP is wouldn't have been wasted for air targets)

(0.072 g *  (960 m/s)^2)/2 = 33.1776 Joules

 

15mm AP round with 72g and 850m/s MV

(0.072 g *  (850 m/s)^2)/2 = 26.0100 Joules

 

20mm AP / API rounds with 115g and 705 m/s MV:
(0.115 g *  (705 m/s)^2)/2 = 28.5789 Joules

 

20mm Minengeschoss is not relevant here because it doesn't rely on kinetic energy for damage. Pls remember that this is only the muzzle energy. Bullets will lose energy with increasing travel distance.

 

Interesting thing is that 15mm HAVAP and 20mm AP/API have quite the same muzzle energy  28.6443 Joules and 28.5789 Joules. The lighter HVAP round will lose energy faster on distance and because of the same muzzle energy potential there is no reason to use expensive tungston ammo instead a conventional 20mm API. So it makes sense to reserve the higher penetration capabilities to fight tank, even though the practical range values do not look good on modern tanks and HVAP do not like angled armor anyways. 15mm API seems better in muzzle energy, but I think the 20mm API close or even better for that + the Minengeschosse have favourable damage potential against soft targets. 15mm has higher fire rate and you must also consider that more bullets per second, however because a bf109 as only 200 round, doesnt matter MG151/15 or MG151/20. More daka per round is better.
 

 

 

 

[LukeFF]

5 hours ago, ZeroCrack01 said:

But if you are right about your thesis, then that would make the 20 mm by far the superior weapon, relying mainly on HE with insane amount of filler compared to other HE rounds. Damaging the plane by fragements and big holes, instead of hitting vitals parts inside the skin. I mean, new DM makes planes literally and far more commonly explode with those rounds. DAKA DAKA

 

Yes, and it was for a very good reason that 109 F-2s were retrofitted with the MG 151/20 - it simply was the better weapon for air-to-air combat.

[II./SG.1-MarkWilhelmsson]

17 minutes ago, LukeFF said:

 

Yes, and it was for a very good reason that 109 F-2s were retrofitted with the MG 151/20 - it simply was the better weapon for air-to-air combat.

 

I think every last person in this thread has misinterpreted what I'm trying to get at. I think the 15mm AP that we currently have in game are correct for the F2 and gunpods on the F4; my purpose for posing this question is that I think the 15mm guns on the Hs129 are not given the correct ammunition that they actually carried for anti-armour work; the lighter and faster Tungsten core AP that could penetrate 48mm of armour at 100m/90 degrees.

Edited May 7, 2020 by II./SG.1-MarkWilhelmsson

[FTC_Zero]

1 hour ago, II./SG.1-MarkWilhelmsson said:

 

I think every last person in this thread has misinterpreted what I'm trying to get at. I think the 15mm AP that we currently have in game are correct for the F2 and gunpods on the F4; my purpose for posing this question is that I think the 15mm guns on the Hs129 are not given the correct ammunition that they actually carried for anti-armour work; the lighter and faster Tungsten core AP that could penetrate 48mm of armour at 100m/90 degrees.

In that case i would look for a source how frequent those round were issued. IMO I would not see any reasons to waste logistic on that. What do you want to fight with that? KV1, forget it. T34 side armor? You wont never ever have 90 deg on 100m and dont crash, slighly more range or angle and everything is immune, unless it is something you could fight with standard mg151/15 and mg151/20 anyways. 

 

Edited May 7, 2020 by ZeroCrack01

[-=PHX=-SuperEtendard]

36 minutes ago, ZeroCrack01 said:

In that case i would look for a source how frequent those round were issued. IMO I would not see any reasons to waste logistic on that. What do you want to fight with that? KV1, forget it. T34 side armor? You wont never ever have 90 deg on 100m and dont crash, slighly more range or angle and everything is immune, unless it is something you could fight with standard mg151/15 and mg151/20 anyways. 

 

Tanks like the Sherman, Stuarts and things like T-70s from the front (with some diving angle) are good cases for using the 15mm apcr.

[II./SG.1-MarkWilhelmsson]

2 hours ago, ZeroCrack01 said:

In that case i would look for a source how frequent those round were issued. IMO I would not see any reasons to waste logistic on that. What do you want to fight with that? KV1, forget it. T34 side armor? You wont never ever have 90 deg on 100m and dont crash, slighly more range or angle and everything is immune, unless it is something you could fight with standard mg151/15 and mg151/20 anyways. 

 

 

I use the Hs129 to hit T34s from the side and about 90 degrees perpendicular to the armour face all day long. I start shooting at 200m and sometimes don't pull off till I'm 50m away or less. It's very slow so it's not that hard, especially with flaps out at 20 degrees. Mostly, I'm interested in being able to use the 15mm against light tanks like T70 and BT7 and for fast kills against armoured cars instead of it taking dozens of hits. 

[=362nd_FS=RoflSeal]

17 hours ago, ZeroCrack01 said:

In that case i would look for a source how frequent those round were issued. IMO I would not see any reasons to waste logistic on that. What do you want to fight with that? KV1, forget it. T34 side armor? You wont never ever have 90 deg on 100m and dont crash, slighly more range or angle and everything is immune, unless it is something you could fight with standard mg151/15 and mg151/20 anyways. 

 

IIRC those rounds were mainly used by HS-129.

You have to remember that even throughout 1942, the Soviet tank force was mainly obsolete light tank types like T-70s, BT-7s and T-26s, and 15% were British Lend Lease tanks, Matilda and Valentine, who were vulnerable in a diving attack vs this gun due to thin top armor.

[Avimimus]

20 hours ago, II./SG.1-MarkWilhelmsson said:

I think every last person in this thread has misinterpreted what I'm trying to get at. I think the 15mm AP that we currently have in game are correct for the F2 and gunpods on the F4; my purpose for posing this question is that I think the 15mm guns on the Hs129 are not given the correct ammunition that they actually carried for anti-armour work; the lighter and faster Tungsten core AP that could penetrate 48mm of armour at 100m/90 degrees.

 

Interesting. The thread on the UB also got me interested in possible ammunition upgrades for later war aircraft (e.g. Yak-9 might have slightly more effective ammunition)... it is subtle, but would be fun to have such details.

 

It'd also be nice if they used the existing 'field mod' system to let us switch which trigger the Mk-101/103 is on... it'd be really easy to do I believe (just create a new entry and change one byte).

[FTC_Zero]

5 hours ago, =362nd_FS=RoflSeal said:

IIRC those rounds were mainly used by HS-129.

You have to remember that even throughout 1942, the Soviet tank force was mainly obsolete light tank types like T-70s, BT-7s and T-26s, and 15% were British Lend Lease tanks, Matilda and Valentine, who were vulnerable in a diving attack vs this gun due to thin top armor.

I can imagine want you say. However without primary sources there is always a dead end.

[=362nd_FS=RoflSeal]

On 5/8/2020 at 9:37 PM, ZeroCrack01 said:

I can imagine want you say. However without primary sources there is always a dead end.

What do you want? The use of the 15mm APCR rounds against tanks or the thickness of the armor of Russian Light tanks and British infantry tanks vs air attack?

[FTC_Zero]

On 5/9/2020 at 11:20 PM, =362nd_FS=RoflSeal said:

What do you want? The use of the 15mm APCR rounds against tanks or the thickness of the armor of Russian Light tanks and British infantry tanks vs air attack?

Quantities, for you it seems enough that it existed. How much was issued in which quantities. As we now, during war 15 mm was completely faded out. Especially with BK gondel weapons might be another rational why such logistical extra work was pointless. But, again, that only an assumption. 

Edited May 13, 2020 by ZeroCrack01

[LukeFF]

1 hour ago, ZeroCrack01 said:

Quantities, for you it seems enough that it existed. How much was issued in which quantities. As we now, during war 15 mm was completely faded out. Especially with BK gondel weapons might be another rational why such logistical extra work was pointless. But, again, that only an assumption. 

 

My research into various primary and secondary sources points to the the 15 mm cannons being retained on the Hs 129 at least until the spring of 1943. From what it looks like, the MG 151/20s only really started being fitted at the same time the MK 103 started being fitted in mid-1943.

Edited May 13, 2020 by LukeFF

[-=PHX=-SuperEtendard]

Looking at the Luftwaffe ammunition handbook, for the March 1943 specification the strike aircraft had the 15mm tungsten APCR as standard issue when attacking armored vehicles.

In the June 1944 spec the strike fighters aren't mentioned for the 15mm anymore; they are mentioned in the 20mm section.

So sometime in between March 1943 and June 1944 the 15mm with APCR was ditched for the 20mm MG 151/20 and the AT work relied on the 30mm only.

Edited May 14, 2020 by -=PHX=-SuperEtendard

[441Sqn_Twang]

On 4/22/2020 at 9:36 AM, II./SG.1-MarkWilhelmsson said:

 

Velocity is the main factor when contemplating armor penetration. If I've read correctly, the projectile weights are not dissimilar enough for that variable to make a huge difference. The slightly higher velocity would be more desirable than the slightly higher mass. An example of this would be the fact that a 55gr 5.56 projectile at 3300fps will cut clear through an AR500 plate while the same plate will stop multiple hits from 150gr 7.62 at 2800fps with ease.

 

Kinetic energy really is a secondary factor when attempting to defeat armour. Sectional density is much more important; sectional density calculates the size of the point wherein the projectiles mass is concentrated at impact. 

 

My reason for asking is that I'm curious if the 15mm AP is better for killing stuff like armoured cars than the 20mm AP.

I think that you need to consider cross-sectional density of the bullet. In this case, a 55gr 5.56mm projectile is close to optimum for that caliber. But a 150 grain 7.62 (.30 cal) has sub-optimal cross-sectional density, and therefore less effective penetration. Try comparing the 55gr 5.56mm round to a 165 gr 7.62mm NATO round, and you will see less of a difference for sure.

 

For the 15mm gun versus the 20mm - the 20mm is 25% greater caliber - that means more than 25% increase in bullet weight. The weights, shapes, ballistic coefficients, and cross-sectional densities of the bullets being fired from these cannon all contribute enormously to their comparative effectiveness - not just the muzzle velocities. A slower bullet with a much greater weight and optimum cross-sectional density will penetrate much farther than a lighter faster, less efficient bullet. For practical proof, look at the nature of hunting cartridges - medium and large bore hunting rifles, and long-range hunting cartridges. What do we know about the projectiles fired from these 15mm and 20mm cannons?

Edited May 14, 2020 by 441Sqn_Twang

[II./SG.1-MarkWilhelmsson]

10 minutes ago, 441Sqn_Twang said:

I think that you need to consider cross-sectional density of the bullet. In this case, a 55gr 5.56mm projectile is close to optimum for that caliber. But a 150 grain 7.62 (.30 cal) has sub-optimal cross-sectional density, and therefore less effective penetration. Try comparing the 55gr 5.56mm round to a 165 gr 7.62mm NATO round, and you will see less of a difference for sure.

 

For the 15mm gun versus the 20mm - the 20mm is 25% greater caliber - that means more than 25% increase in bullet weight. The weights, shapes, ballistic coefficients, and cross-sectional densities of the bullets being fired from these cannon all contribute enormously to their comparative effectiveness - not just the muzzle velocities. A slower bullet with a much greater weight and optimum cross-sectional density will penetrate much farther than a lighter faster, less efficient bullet. For practical proof, look at the nature of hunting cartridges - medium and large bore hunting rifles, and long-range hunting cartridges. What do we know about the projectiles fired from these 15mm and 20mm cannons?

 

Again, I mentioned sectional density in the exact statement that you quoted from me.....

[Yogiflight]

2 hours ago, 441Sqn_Twang said:

For the 15mm gun versus the 20mm - the 20mm is 25% greater caliber

33%, 5mm is a third of 15mm. The 15mm is 25% smaller than the 20mm.