hispano vrs. Mg151

[Flyboy]

does AH modell diferent shells? do we have both HE and AP rounds when we fire our guns?

that can explain alot of irregularity in the DM. sometimes it takes 20 rounds sometimes 2

[HoHun]

Hi Charge,

>Edit: From another forum:

Hm, I calculate about the same kinetic energy, but twice the chemical energy. I'm using Tony's data, 4.184 J/cal, 1.335 kcal/g for chemical energy.

>Well if you don't and calculate 151/20 power by using the correct power output of Mine with PETN what would be the result for 151/20?

Well, I've not gone into exact chemical compositions because

a) It's not easy to find out which explosive what used in which shell.

a) There is a certain uncertainty about the exact composition of each explosive.

b) Chemical energy and destructive capability are not always linear for different explosives anyway. (The improved mine shell had less than 40% more energy for 40% more destructiveness.)

I looked at blast front velocities and the like and then decided to leave it at a standard energy content since more detail was as likely to introduce new errors as to improve accuracy.

>Where did U get that 40% increase in explosive power?

For example a reproduction of WW2 weapon data in the German Waffen Revue magazine.

>Well if you don't and calculate 151/20 power by using the correct power output of Mine with PETN what would be the result for 151/20?

An inaccurate figure ;-)

But I could pretend the improved mine shell had 40% more energy (which it hadn't) to arrive at the following comparison:

MG 151/20: 2,25 MW vs. 1,71 MW (at a pure Mine shell loading)
MG 151/20: 1,59 MW vs. 1,27 MW (at 1:1:3 API/HET/Mine)
MG 151/20: 1,43 MW vs. 1,16 MW (at 1:1:2 API/HET/Mine)
Hispano II: 1,06 MW (at 1:1 API/HE)
MG 151/20: 1,15 MW vs. 0,97 MW (at 1:1:1 API/HET/Mine)

Regards,

Henning (HoHun)

[HoHun]

Hi Gscholz,

>IIRC the MG151/20 belting was initially AP - HE(M) - HE(T) - HE(M). Later they changed it to AP - HE(T) - HE(M) - HE(M) which would give the HE(M) better grouping, thus better chance of causing catastrophic damage to bombers.

Four mine shells in a row have yet better chances of causing catastrophic damage, so why stop at two?

There's little data with regard to belting, and the Luftwaffe calculations regarding bomber destruction seem to assume a pure mine shell loadout.

(By the way, one MG 151/20 mine shell carries pretty much the same explosive energy as two Hispano HE shells.)

Regards,

Henning (HoHun)

[Angus]

Why stop at two?
Good question.
Reliability? AP desire for things like fuel tanks and armour?

Don't really know.

Hope Tony pops in and informs us.

[MANDO]

Originally posted by HoHun
Four mine shells in a row have yet better chances of causing catastrophic damage, so why stop at two?

May be because the nature of the mine itself. The mine is going to provoke a blast of very high pressure air. The HE is going to provoke the same at minor scale, but, at the same time, is going to spread very fast metal fragments able to penetrate any non armoured part of the plane nearby.

For example, if a mine explodes near a fuel tank, the fuel tank may end fully deformed. The same case with HE will result in a  perforated fuel tank.

[rshubert]

How does the fusing of a mine shell differ from that of an impact fused HE round?  I must admit I have never heard of the type.



shubie

[Kurfürst]

Originally posted by MANDO
May be because the nature of the mine itself. The mine is going to provoke a blast of very high pressure air. The HE is going to provoke the same at minor scale, but, at the same time, is going to spread very fast metal fragments able to penetrate any non armoured part of the plane nearby.

For example, if a mine explodes near a fuel tank, the fuel tank may end fully deformed. The same case with HE will result in a  perforated fuel tank.

Both mine and ordinary HE produces fragments, but these fragments when speaking of 20mm shells are tiny and very weak. I have detailed report on the german MG C30 20mm cannon, a far more powerful weapon than either the Hissy or the Mauser. One would expect bigger fragments from it, but even that 20mm gun`s fragments stopped after piercing a few layers of very thin dural plates. In fact, most fragments stopped after the 1st or 2nd dural plate. On an aircraft, I`d suppose the framents would stop immiadately at the first heavier structure encountered - main spar, ribs, radios, any kind of armor or thicker plate etc.

The german mix of ordinary HEI with mine shells was probably due to increase the incendinary effect of the mix, and to add heavier fragments, but remind you, the explosive in the mine shells was already highly potent at that, the mix itself being incendinary to start with, and so were the hot fragments it spread out in the nearest vicinity. British live fire tests showed fairly high, and comparable fire probability with either type of HEI or Mine shells.

I have did some calculation on the Hissy/Mauser subject a while ago, and the numbers were very convincing. The combination of 25-33% higher ROF, the use of much higher percantage of explosive shells (80% vs. 50%, ~50% higher), and the fact that the Mines carried about 3-4 times the explosive than an Hispano HEI shell (plus the LW`s explosives were somewhat more potent than the RAF`s choice).. you have very high advantage on the Mauser`s side on Chemical Energy, and it most likely translates to greater overall energy.

[MANDO]

Kurfürst, looking at the section of a mine round, it really dont have anyway to produce destructive metal fragments, it has a very very thin metal cover. HE rounds are really different in design. Both are different rounds for different purposes.

[Kurfürst]

You are right in that the material immidiately surrounding the explosive filler is very thin, so the fragments will be of very small size, but numerous. Exploding next to the pilot, cables, fuel/coolant/electric lines, they still cause damage to them. IMHO it`s not OK to think mines don`t produce fragments at all.

There`s a lot more though in the base and the head to form fragments from. Simple math tells us that substracting 18 gram explosive from the 92gram weight of the total body will still leave us 74 grams of potential fragments.

[HoHun]

Hi Mando,

>For example, if a mine explodes near a fuel tank, the fuel tank may end fully deformed. The same case with HE will result in a  perforated fuel tank.

Well, the fragments from a 20 mm shell are very small, and self-sealing tanks are capable of sealing rifle-calibre sized leaks quite well, so that's not a case for HE over mines.

Mine shells had some fragmentation effect as well, but the main energy went into the blast, not into the fragments. 20 mm HE fragments probably were fewer but larger, but could only damage the highest-vulnerability components, such as control wires or hydraulic or fuel lines, or harm the crew.

Since the idea behind the mine shell was to avoid the necessity of having to aim for the few vulnerable components by damaging the structure itself, the benefit of the trade-off was highly favourable for the mine shells.

Regards,

Henning (HoHun)

[Angus]

Came to think of this thread since I was calibrating my rifle telescope

Just HE's with very thin skin will do a lot of damage  under some angles, or just not.
Vice versa with the AP.

I shoot a bull with a metal cased bullet, while I use a hollow point for birds, if you see what I mean.

[Tony Williams]

Originally posted by Angus
How is the ballistic of the mineshell. Same?

Oh, and for your info (you probably already know?), some Spittys had the late Orlikon cannon.

Pilots were highly impressed with it. Just a couple of hits...

??? RAF planes never carried any 20mm cannon except Hispanos, and Spitfires never carried any other cannon of any calibre that I'm aware.

Well, all right, the F4 Phantom II had a 20mm M61 gunpod but that's a bit out of our timeframe

Tony Williams: Military gun and ammunition website and Discussion forum

[Tony Williams]

Originally posted by Charge
"The Hispano 20mm HE round had 8% HE by weight (per Tony Williams website), the MG151 HE had 3.2%, the API had 3.1%, and the Mine round had 22%."

"You've got to draw a line somewhere :-) "

Well if you don't and calculate 151/20 power by using the correct power output of Mine with PETN what would be the result for 151/20?

PETN by itself was too sensitive to be used in ammo - it was likely to detonate when you didn't want it to. Well, the Japanese used it, but then...

Tony Williams: Military gun and ammunition website and Discussion forum

[Tony Williams]

Originally posted by Angus
Why stop at two?
Good question.
Reliability? AP desire for things like fuel tanks and armour?

Don't really know.

Hope Tony pops in and informs us.

I've popped.

Basically, the ideal aircraft projectile would penetrate deeply through any armour, have a huge blast effect, and also throw incendiary material around all over the place. You can only achieve this in one shell by going to a very large calibre, so the 20mm rounds had to specialise in one or two elements.

The belt mix was an attempt to achieve all of the above effects but it wasn't an exact science as there was a lot of luck involved. It worked fine if your AP projectile happened to strike the armour and the HE hit a fuel tank, but it wasn't much good the other way around...

Incidentally, the main reason for the Germans retaining the old HE-T design was that the 20mm mine shell couldn't take a tracer.

Tony Williams: Military gun and ammunition website and Discussion forum

[Tony Williams]

Originally posted by Kurfürst
Both mine and ordinary HE produces fragments, but these fragments when speaking of 20mm shells are tiny and very weak. I have detailed report on the german MG C30 20mm cannon, a far more powerful weapon than either the Hissy or the Mauser. One would expect bigger fragments from it, but even that 20mm gun`s fragments stopped after piercing a few layers of very thin dural plates.

The HE shell for the C30 was similar in size to the Hisso's so the effect should be comparable. Striking velocity makes no difference to fragmentation.

Tony Williams: Military gun and ammunition website and Discussion forum