Hispano vs Mg151 (no whine)

[Wilbus]

Not a whine, so all you whine police dweebs might aswell leave now.

Hazed posted a nice interesting chart a while ago, comparing US aircraft weapons with eachother.

Thought I'd throw in the MG151 in the test and calculate the way they have.

Weight of fire is equal to "number of rounds fired per minute".

Lethality is equal to "weight of fire * Velocity^2 (raised to 2) * 10^-8.

MG 151 rate of fire: cirka 700 rounds per minute. I'll calculate with 700/min.

(The 650 rounds/min is when equiped on a Ta152 with prop spinning.)

Muzzle Velocity: 805 m/s (2641,1 feet/s)

Weight of bullet (M-Geschoss = High explosive, used against airplanes) 197,2 g (0,4348 lbs).

My calculations may be wrong but I don't think so. Think I've calculated it right.

Weight of fire (lbs/min) Weight: 0,4348 * 700 = 304,36 lbs/min.

Lethality: Weight of fire * Muzzle Velocity^2 * 10^-8

304,36 * 2641,1^2 * 10^-8 = 21,23

So acording to these calculations, the Mg151 has greater lethality then both the 1941 M2 20mm, and the 1944 M3 20mm.

[Wilbus]

This is the chart Hazed posted.

[MANDOBLE]

Wilbus, you are calculating the lethality of M-Geschoss projectiles based on its weight and muzzle vel like if they were normal AP shells. This is wrong. The mine projectiles are going to explode upon impact, so, even at much slower muzzle velocities they are going to cause similar damage. This is (should be) just the big advantage of the mines, no matter the range, no matter the energy, just hit the enemy and they explode like small hand grenades.

Your formula may be good for normal AP projectiles, very dependant on its weight and muzzle vel.

And two questions about AH modeling:
Do we have M-Geschoss in AH?
Do mines lose destructive power with the range?

[Wilbus]

I calculated it to go with the US test, meaning, that without the HE (as has been left out of lethality on the US guns aswell) the Mg151 should be more leathal. Add HE to this and it would probarly be more leathal as it contained more HE.

But the test is calculated acording to no HE, lethality is no HE just impact and destructive power. I've calculated the same way for the Mg151.

[Wilbus]

To put it short, explosive power isn't in the test at all, not for the US nor for the MG151.

[GScholz]

Wilbus, I think you may have underestimated the 151. A HE round is typically lighter than an AP round (steel or tungsten is heavier than the explosive compound). If the US chart submitted calculate with the weight of 20 mike-mike AP shells you should look for the weight of a German AP shell (if they used one). I think you would see a significant increase in 151 lethality.

Another note: Had the M-Geschoss a proximity fuse, or a delayed detonation fuse? The latter would be more effective against heavy-bombers as they explode inside the aircraft.

[FDutchmn]

I am not an expert but I thought this would help... just what I did a long time ago when I was flying Air Warrior...

Please take a look at this table:

Data for this table was borrowed from:
Emmanuel Gustin's Extensive Military Aircraft Database
Vermillion's Website
R. Shaw, Fighter Combat, ISBN 0-87021-059-9
J. Horikoshi and M. Okumiya, Reisen, A small history of the Japanese Naval Aviation, ISBN4-257-79028-8
Magazine Maru Editorial Department, Shiden, Shidenkai, and Type94 Float Plane, ISBN4-7698-0631-0

I took the data from Emmanuel Gustin's Extensive Military Aircraft Database first and then filled the missing parts from Vermillion's Website like the information on explosives and the projectile weight for the Ho-5 cannon. I also used the information on TNT as Vermillion presented which stated that the amount of TNT is proportional to the weight of the projectile. However, I notice that Vermillion's website has moved elsewhere.  

Well, depending on the type of projectile it is, the proportion would vary I suppose, together with the type of explosive.  But assuming that each of these guns had similar projectiles for the sake of comparison, this table might be of benefit.

I noticed that the energy given off by the explosive is quite high in comparison to the kinetic energy of the projectile itself.  Given the distance the projectile has to travel (and the loss of kinetic energy), the energy of the explosive will become more pronounced, I think.

Lastly, if anyone could enlighten me... I believe the table that Hazed posted comes from Mr. R. Shaw's book, Fighter Combat.  There, I notice that the lethality is not calculated in the form of kinetic energy, but a formula something close to it.  Is this an accepted method of calculating lethality or are there other methods for this?

Just wondering and my two cents on this issue...

[Wilbus]

Fdutchman, the chart you posted shows the velocity of the Panzergranate (AP) and Brandsprenggrante (Fire high-explosive shell). Velocity of those is 705 m/s. M-Geschoss had 805 m/s.

Calculations for AP and Fire Grenade shells.

Velocity: 705 m/s (2313 ft/s).

Weight of bullet: 223 g (0,4916 lbs)

Weight of fire (lbs/min) 0,4916 * 700 = 344,12 lbs/min.

Lethality: 344,12 * 2313^2 * 10^-8 = 18,41.

18,41 using AP shells.

[Bombjack]

Wilbus, I think perhaps your chart has the MG151 cartridge weight, rather than the projectile weight. The M2/Hispano Mk2 projectile was considerably more massive than that of the MG151/20 (whether M-Geschoss or AP/HE).

(edit)

Regardless of this, I think the 'weight of fire' theory is barely adequate as any measure of a gun package's effectiveness. It disregards not only HE component, which became ubiquitous as the war progressed, but penetration considerations too.

[Pyro]

What Bombjack said.  Those figures are for the weight of the entire round.  The projectile weights you're looking for are 92 g and 115 g respectively.

[Wilbus]

Discussing the "lethality" thing Bombjack.

You may very well be right on the weight thing though, it's probarly the complete shell.

I wounder a thing though, is the MG151 modelled with 705 m/s or 805 M/s???????

[Wilbus]

Thanks Pyro, my misstake, wrote my above message right as you wrote yours I think.

May I ask what velocity our have? Don't matter to me if it is 705 or 805, just interesting to know.

Please don't think I am trying to say anything is wrong or that I am whining cause I am not, just asking

[Bombjack]

Wilbus, obviously I don't know what velocity the shells have in AH, but it would be realistic for them to travel at different speeds if they were M-Geschoss vs AP. The Mine shells weighed less like Mandoble says, so with the same cartridge (same amount of propellent) as the AP/HE shell, they actually gained a higher muzzle velocity.

However this lack of density (as well as a slightly less aerodynamic shape) counts against the Mine shell in range, since it slows more quickly.

A quick digression on the subject of "Mine shells are unaffected by low velocity, they are effective even at extreme range": imagine you hold a firecracker in your open palm and it goes off, what happens? You burn your hand. Now close your fist around that same firecracker... your wife's going to be opening your mail for you for the rest of your life.*

Same deal with an explosive shell. We're not looking at grenades here, if they go off outside the skin of the aircraft their effectiveness is going to be low - they need to have enough velocity left to penetrate before they explode. Mine shells slow down very quickly, that is why their effective range is low.

(edit, so people don't think I'm down on the MG151)

Of course, if that shell gets through into an enclosed space where the blast is contained... then you're looking at serious damage. Swings and roundabouts, you gain in one area, you lose in another.

* crap film, but I like the quote

[Wilbus]

Same deal with an explosive shell. We're not looking at grenades here, if they go off outside the skin of the aircraft their effectiveness is going to be low - they need to have enough velocity left to penetrate before they explode. Mine shells slow down very quickly, that is why their effective range is low.

Yup I knew that, who said anything else?

(edit, so people don't think I'm down on the MG151)

Really sucks to always have to protect yer self from flames by saying such things don't tou think?

[Tony Williams]

Re. the Dutchman's table: there were considerable differences in the percentage weight of HE in the shells used by different nations.

The Germans focused on blast effect initially, with the 20mm M-Geschoss clocking 19-20g HE in a 92g shell (20%). Other types of shell generally managed no more than 10%; e.g. the Hispano loaded around 10-11g in a 130g shell. The Soviet shells were typically only around 6-8%. The Japanese varied quite a bit.

Towards the end of the war, the Luftwaffe moved away from blast effect in favour of incendiaries, as fire was the big bomber-killer. They developed more strongly-built and heavier M-Geschoss (so they would penetrate more deeply) loaded mostly with incendiary material, and with hydrostatic fuzes which detonated only when they hit a fuel tank. Nasty - but very effective.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/