A look @ the Ho-103 the US 50cal and 2 others

[Vermillion]

Lets put this into perspective.

Now to use some rough numbers I worked up real quick.

Lethality (effectiveness) is roughly proportional to applied energy.

At the muzzle, the applied energy for one solid round of MG ammunition is:

12 kJ   Type I 12.7mm (Japanese)
9 kJ MG131 13mm (German)

Assuming one gram of TNT, your total energy is approximately 4.1 kJ/gram. PETN or other high order explosives deviate from TNT in energy production by within 10%, so for a rough number lets assume TNT. So your talking about adding to the total effectiveness approximately:

4.1 kJ/shell

Now at first your gonna say "WOW! A 30%-50% increase in lethality.

But unfortunately (and there's always a "But") it doesn't work that way. Only a small fraction of that total explosive energy gets applied to the total due to the nature of how explosive forces and shockwaves work. How much, I still haven't gotten a handle on myself and maybe Tony or someone else can comment. But I would say less than 20% of the total explosive force would be applicable (a total wild bellybutton guess on my part).

So now your talking less than 0.8 kJ/shell increase in lethality.

This comes out to be about a total 6%-8% increase in effectiveness per shell and thats before you consider issues such as  fuzing, less actual applied Kinetic energy due to it having less mass (HE versus AP), and many others.

So are we really talking about alot of difference?

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Vermillion
**MOL**, Men of Leisure

[funked]

Vermillion I'm pretty sure you can't just add the energies like that.  20% is probably VERY generous.

[Jigster]

I believe the orginal intentions of these shells were for starting fires...that is easily enough explosive to destory fuel lines, fuel tanks, and/or sever other critical line (at least easier then ball or AP, AP/I aside.) The damage model in AH really isn't quite complex enough for them to have much effect.

- Jig

Btw I hope some day I can shoot a tracer stream into a leaking fuel stream and catch that plane on fire  

[Tony Williams]

 

Originally posted by Hooligan:
AGW:

The Germans were, to put it mildly, rather serious about HE, and since they only managed to get about 1g of PETN in their 13mm HE rounds I am assuming that nobody else did much better.

However, you clearly know a lot more about this than I do and I am looking forward to hearing what you dig up when you get access to your sources.

Hooligan

I've checked what sources I have (my best one is unfortunately with someone else at the moment) and I have to admit that you're right.  The best figure I can get for the MG 131 is 1.3g, although that is a tracer round so there would be more space for HE if that were omitted.  The only reference I can find to the Italian 12.7mm is 0.8g.

What I have discovered is that that filling weight is the statistic least often quoted!

Tony Williams
Author: Rapid Fire - The Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces.
Details on my military gun and ammunition website: http://www.users.globalnet.co.uk/~autogun/

[brady]

  This Question on the weight of filling has proven to be a bit vexing,my sources give empty weight of the projectiles. At this point we are left with "best guess" , a look at the comparative volume of the "fuseless" HEI round for the H0-103, would suggest that it could carry at least 1 gram of explosive, the other Japanese rounds being more comparable to the MG 131 , and the US .50 cal would contain amounts approximately equal to and slightly greater than respectively.

  Now in terms of the destructive power of the round on target, Vermillion did some nice number crunching and this helps to better illuminate, a cloudy issue.

  I think after all is said and done it could be safely said that the HEI round bring something to the party that the basic ball round does not, the ability to NOT make a nice clean hole in the target, to not just put a hole in the fuel tank but to set it on fire,...

  so the Ho-103 at a normal combat range of 300, 400meters, spewing a steady stream of HEI rounds with a few AP rounds thrown in for color (they being the tracers), is going to deal out death at 900rpm, I ask u gentlemen if your target was another aircraft what gun would u want to have in your plane?

Brady


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[This message has been edited by brady (edited 01-10-2001).]

[Hooligan]

I believe that in the 12.7mm range armor penetration is very important.  AP/I is probably the best ammo for these guns and the .50 is probably a better choice due to its better penetration and ballistics.

Hooligan

[Vermillion]

Funked, thats what I'm saying.

Even if you "generous" and give it 20%, it still doesn't make enough difference for us to argue the fact for Aces High.

Hmmm.. I think I just thought of a way to at least find a ball park number for what percentage of that explosive value to use for rough comparisons. If I figure it out, I'll pass it on.

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Vermillion
**MOL**, Men of Leisure

[Manx]

A visual aid  

   

Sorry, couldn't find a ma-103 at Aberdeen.

[This message has been edited by Manx (edited 01-12-2001).]

[brady]

 Nice pic Manx, i wish my photos turned out a little better from when i was their  .


 The Ho-103 HEI(fuseless) round is a full 2inches in length,the 13mm MG 131 round is around 1 37/64 inches without the fuse, obviously the H0-103 has the bigger bang in this size range, do to the larger HEI capacity of the round, when compared to the US or German rounds in this range.

Brady

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[This message has been edited by brady (edited 01-12-2001).]

[Tony Williams]

I have now heard from Ted Bradstreet, who almost certainly knows more about Japanese aircraft guns and ammunition than anyone else (certainly a lot more than I do!).

He has information on the naval rounds, and quotes 2.8g HE for the 13mm Type 2 (basically the same as the MG 131), although only 1.5g for the (13.2mm) 13mm Type 3.

Based on this, he suggests 2.5-3g for the Ho-103.

Tony Williams
Author: Rapid Fire - The Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces.
Details on my military gun and ammunition website: http://www.users.globalnet.co.uk/~autogun/

[brady]

  TY, Mr. Williams  

Brady

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[This message has been edited by brady (edited 01-14-2001).]

[Spritle]

That picture is a lot more help than you might think.  Volume of the cylinder is Pie R^2 H.  Now all you need is the specific gravity of your HE and you will have the amount carried by that round.  Assuming that the cross section shown is right down the middle you know the diameter is 13mm then using ratio's you can determine the i.d. of the cylinder and it's height.

Also Vermillion, remember this there are reports of Migs returning to base with MANY .50 cal holes all over the place, but I don't think that many Sabers made it back with an equal number of holes.

While ball ammo has certain benefits in the armor piercing area it is somewhat limited when hitting non-armor protected areas like any place but the cockpit.  

Your 20% WAG might be a little conservative.  If ball ammo were so great then aircraft would still be using it today.  

It's pretty easy to see how a very rapid increase of pressure in small-enclosed volume like a wing tank can cause catastrophic failure.  Try putting an ounce of alcohol into a 1-gallon metal gas can when the air temp is around freezing. Then close the lid and start adding heat.  By the way you might want to stand WAY back!  

Now take another can and shoot it with ball ammo.  Let me know which one makes a bigger hole.

Spritle

[Hooligan]

Ball ammo isn't that good.  That's why nobody used it much by war's end.

In general HE causes a big hole and lots of damage near the surface.  AP/I or APHE penetrates deep into the aircraft and potentially hits a vulnerable component (like an ammo box).  Both types of rounds have their advantages, which is better depends a lot on the target characteristics.

Hooligan

[Jimdandy]

 

Originally posted by Spritle:
It's pretty easy to see how a very rapid increase of pressure in small-enclosed volume like a wing tank can cause catastrophic failure.  Try putting an ounce of alcohol into a 1-gallon metal gas can when the air temp is around freezing. Then close the lid and start adding heat.  By the way you might want to stand WAY back!  

Now take another can and shoot it with ball ammo.  Let me know which one makes a bigger hole.

Spritle

LOL! That reminds me of when a friend of mine left a can of green beans in the fire. You would have thought it was HE. I'm just glad all we were around to hear was the explosion. If we would have been standing there it could have been deadly. A little heat and a little expansion.   Also a similar effect is a safety slug. We shot a plastic milk jug filled with water with a 12 gage. You can imagine the result. Then we fired a .45 automatic pistol round at another jug filled with water. The rounds were safety slugs that on impact split into several fragments and release several BB sized pellets. The effect of the .45 round was the same as the 12 gauge. The safety slug was far more efficient in its energy delivery than a ball slug. Now if even that little .45 cal round had some HE inside the effect would be even more dramatic.

[Tony Williams]

 

Originally posted by Hooligan:
In general HE causes a big hole and lots of damage near the surface.  AP/I or APHE penetrates deep into the aircraft and potentially hits a vulnerable component (like an ammo box).  Both types of rounds have their advantages, which is better depends a lot on the target characteristics.

Hooligan

It's really a question of armament philosophy.  The USAAF mainly chose a battery of high-velocity .50 HMGs for their fighters.  This meant that they destroyed aircraft by riddling them with AP bullets which in many cases would go straight through.  

The Luftwaffe was in the opposite camp.  They chose a small number of lower-velocity cannon (latterly 30mm) firing high-capacity HE shells fuzed to detonate within the aircraft structure, causing structural failure.

Both systems worked, but they had different targets.  The USAAF was generally only engaging enemy fighters, the Luftwaffe had to deal with heavy, well-armoured bombers.

The best all-round compromise in WW2 was probably the RAF's fit of four powerful, high-velocity 20mm cannon, loaded alternately with HE/I and SAP/I.  These weighed little more than six .50s (less for the Mk V version) but had about twice the destructive effect.

In Korea, the USAF stuck to .50s and found the MiGs hard to shoot down.  They switched to 20mm shortly afterwards.

Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website: http://www.users.globalnet.co.uk/~autogun/index.htm


[This message has been edited by Tony Williams (edited 01-16-2001).]