AP vs HE ammo comparizon/calculations

[LLv34_Stafroty]

Reason i do this is to point out the difference of damage cannon HE ammo does compared to AP style of ammo, like machinegunshave.

Exploding cannon ammo tears target area a hole, plus makes fragments flying around the hit zone as well making plane partsthemselfs as fragments too.

AP ammo does go though the areas it hits, making holes bit over its caliber while doing it.

 example. there is aluminium bar 200mm wide. to cut it completelly it takes 26,2 pieces of 7,62 ammo, 15,74 pieces of .50cal

ammo, IF they shoot in direct line next to other at shortest route thru the bar. to cut it with 20mm HE it would take under 2

hits, 1 might easily be enough, depending the HE ammo in question. if its just 20mm AP, it would take 10 hits, same way like

for machineguns.

what is not same for weapon damage is the penetration what AP rounds do, they dont stop(explode) at first thing they hit, but

they keep going, untill they hit something which stops it, or untill they fly through entire plane, which then means that the

rest of its kinetic energy is wasted totally. It means that it was not able to transfer it all to target in that case. If it

hits engine, it would give all it has, or some other parts, or going through many parts. it depends alot where that AP hits.

it might do very little of its potential kinetic energy.. or not. Right now, every AP round seems to do full amount of its

kinetic energy, no matter where and what angle you hit the target.

Cannon ammo with HE, it eplodes right when it hits, or after little delay,depending of the fuse it has on it. early fuses did

exlode in contact, which reduced their effect quite amount. If it was delayed, it most likely exploded inside the plane,

making much more damage. also when HE shell explodes, it sends fragments nearly at every direction from explosion at high

speed. Sizes of those fragments were different  for different ammo. thin shell minengeschoss ammo did make only small

fragments, which affected only short distance, but there was lots of them. normal HE rounds made different sizes of fragments,

some bigger some smaller etc, that means they had more kinetic energy and weight to keep it longer fly time. and were able to

penetrate deeper, but fragment is like AP round after all, depending of its size makes its "caliber".


right now wings and every other parts of planes have hitpoints, which is reduced based on damage weapon does in

kinetical/chemical way. i believe that its totally wrong to count only on that way of calculating damage.
you can also calculate, or add to energy calculations the damage they in real did, i did really simplified calculation about

that, which i think, would be more realistic, if those results and kinetic energy results would be somehow mixed to find

realistic balance between damage made by different ammunition(calibers)

at least, those numbers here tells some story, which energy based calculations are not able to tell. and everyone is able to

find evidence from WW2 time pictures, from hits machineguns to cannon hits of various calibers/ammo. From those these are

counted/estimated, comparing hole sizes to human head etc. thats what they in real did, not in calculation tables in paper.

So, should it affect flying behaviour how much, if plane takes 50 hits from machinegun on its wing, or 5 hits from cannon on

its wing? what would affect it more? just look the data below.



single shot area effect on sheet of aluminium:

          
gun/caliber         Amount of needed 7,62 ammo to tear as big hole to target

7,62               = 1      7,62
12,7(.50cal)       = 2,7    7,62
20mmAP             = 6,9    7,62
20mmHE (15cm hole) = 392    7,62
20mmHE (20cm hole) = 690    7,62
20mmHE (30cm hole) = 1552   7,62
20mmHE (40cm hole) = 2760   7,62
30mmHE (60cm hole) = 6214   7,62
30mmHE (80cm hole) = 11047  7,62
30mmHE (100cm hole)= 16712  7,62
30mmHE (120cm hole)= 24856  7,62



1 second burst area damages from single weapon measured as how many 7,62 bullets it needs to do same size of hole


light mg 7,62 rof 1200             = 1200     7,62
 
12,7(.50cal) rof 800               = 2160     7,62

MG151/20mm AP rof 700              = 4830     7,62

MG151/20mm HE rof 700(15cm hole)   = 274400   7,62

MG151/20mm HE rof 700(20cm hole)   = 483000   7,62

hissz/20mm HE rof 800(15cm hole)   = 313600   7,62

hissz/20mm HE rof 800(20cm hole)   = 552000   7,62

hissz/20mm HE rof 800(30cm hole)   = 1241600  7,62

MG151/20mm HE rof 700(30cm hole)   = 1086400  7,62

MG151/20mm HE rof 700(40cm hole)   = 1932000  7,62  

MK108/30mm HE rof 650(60cm hole)   = 4039100  7,62

Mk108/30mm HE rof 650(80cm hole)   = 7180550  7,62

MK108/30mm HE rof 650(100cm hole)  = 10862800 7,62

MK108/30mm HE rof 650(120cm hole)  = 16156400 7,62

20mm HE, german     6-10 g of HE
20mm Minengeschoss  18 g  of HE
20mm hispano HE     10 g of He (early?) didnt find other info about wartime ammo
US 37mm M4          45-48 g of HE  this might do hole around 40-60cm range.
MK108 Minengeschoss 72-85 g of HE

i assume, that 20mm cannon holes above 15-20cm  are made with minengeschoss ammo, which had much more HE in them compared to

normal HE ammo. i put many different sizes of holes because i dont have exact figures of hole sized made by different HE ammo.
Mk108 hole sizes arent estimated from any picture, but i believe strongly, that its effect with HE and minengeschoss ammo was

much bigger than with 20mm ammo, as it had 5-14 times more HE in its ammo compared to 20mm HE ammo.
also i havent taken in account the effects of fragments and lets say they are included in calculations.
 

[Sternjaeger]

..not sure what this is all about? 

[JimmyGiro]

Good effort Staffy,

 

I see this as an example of a 'paper-scissors-stone' type of problem, where each type of weapon is better suited for a particular target type. That in turn leads to target specific analysis, which would imply as many ammo types as there are target types.

 

Hence we have typically heavy bomber targets, which need a corresponding heavy [explosive] calibre round; and highly manoeuvrable fighter plane targets, which required high-velocity and profusive [shot-gun] rounds, so as to connect some hits.

 

So the best all-round ammo type for any situation an interceptor might typically encounter would have the characteristics: high muzzle velocity; high rate of fire; 'semi-penatratable', whilst being explosive. These are the qualities of the 20mm Hispano cannon and its ammo.

[Sternjaeger]

So the best all-round ammo type for any situation an interceptor might typically encounter would have the characteristics: high muzzle velocity; high rate of fire; 'semi-penatratable', whilst being explosive. These are the qualities of the 20mm Hispano cannon and its ammo.

 

..when it didn't jam ;-) note that the API-T rounds were discontinued and used only according to the missions, the problem with these is that whilst generally being good for air to air combat, when used on the ground they didn't do enough of neither of its functions.

[Anw.StG2_Tyke]

Good effort Staffy,

 

I see this as an example of a 'paper-scissors-stone' type of problem, where each type of weapon is better suited for a particular target type. That in turn leads to target specific analysis, which would imply as many ammo types as there are target types.

 

Hence we have typically heavy bomber targets, which need a corresponding heavy [explosive] calibre round; and highly manoeuvrable fighter plane targets, which required high-velocity and profusive [shot-gun] rounds, so as to connect some hits.

 

So the best all-round ammo type for any situation an interceptor might typically encounter would have the characteristics: high muzzle velocity; high rate of fire; 'semi-penatratable', whilst being explosive. These are the qualities of the 20mm Hispano cannon and its ammo.

 

I don't think that we have to make this theorycrafting out of it, simply because we know what Ammos were loaded in which conditions. I know it for the German Fighter, they had enough Ammo types to chose and they had to make their own decisions which ammo they want to use on the next mission.

So far, Fighter who operated against Bomber chose another Ammo composition than Fighter who fought again Fighter. Furthermore the whole how big the hole thing is too dumped down. One Minengeschoss made another hole than one AP bullit. But AP bullets could make holes and damage the plane where Minengeschosse wouldn't do anything.

 

 

 

right now wings and every other parts of planes have hitpoints, which is reduced based on damage weapon does in

Where is this stated, that in our current damagemodels wings have some kind of hitpoints? I don't think that this is the case, because I truely can feel a difference between some 7.62 hits and one 20mm hit in a wing.

[BeastyBaiter]

Staf is over thinking this in my opinion. It's quite simple:

 

a) AP is good at punching little holes in stuff that's hard to punch holes in.

b) HE is good at punching big holes in stuff that's easy to punch holes in.

 

If you want to kill a plane engine, use AP. If you want to blow a giant hole in the wing, use HE. If you want to kill the pilot, HE is better if unarmored, AP is better if armored. That pretty much sums it up.

Edited June 23, 2014 by =LD=King_Hrothgar

[Sternjaeger]

Staf is over thinking this in my opinion. It's quite simple:

 

a) AP is good at punching little holes in stuff that's hard to punch holes in.

b) HE is good at punching big holes in stuff that's easy to punch holes in.

 

If you want to kill a plane engine, use AP. If you want to blow a giant hole in the wing, use HE. If you want to kill the pilot, HE is better if unarmored, AP is better if armored. That pretty much sums it up.

 

well not really. Penetration in HE is also a determining factor, not to mention the angle of impact: when flying behind someone it wouldn't be uncommon to see some of the rounds bouncing off the enemy aircraft, kind of like when you skip stones on a lake.. We use a very simplified rendition as it is, let's at least ensure it's accurate.

[LLv34_Stafroty]

hi Jimmy!

 

oops, the values are 60 times too big i forgot to divide rate of fire with 60 to get it at seconds

 

ive always been bugged the way damage is calculated between different ammunition.

 

AUVA, tell me how they count how much wing can withstand before it breaks, if they dont have any damage value for gun, and structure resistance value(hitpoints) for parts.

Of course in game light machine gun makes less damage than cannon hit. many times more. im not here claiming that machine gun round is same as cannon round. quite the opposite.

but its just hitpoints after all with all the parts. and perhaps there is also critical change as well. dunno.

 

how can you test if wing etc have hitpoints?  take custom mission, set it so you have bomber in ground where you are, use its gunner to shoot at target plane, which is also in ground. shoot at its wing, and look at it, how its graphics change according its HP status. i bet it goes always the same way, always the holes etc appear in same order and in same spots in same amounts until wing falls off. thats your hitpoints/health bar for wing. same applies to other parts as well.

 every model has its own style how that health bar is shown thru graphical engine.  when you perfrom these test good, you can really learn how much hitpoints in % you have left on ur wing/other parts.

 

just count how many hits wing can take, before it breaks, do this few times. shoot always at same spot. then, shoot half of needed amount to wing, and then look how it looks, now you know what it is when 50% HP is left.  shoot if off. new target. shoot it 25% of needed amount, check it, now you know what it looks like when it got 75% HP left...

come to report when you have tested that

 

 

 

its true that He ammo isnt traveling long distance inside plane if it explodes, but in turn, it will also send fragmenst around it..

 

the calculations are really simple.  i did also calculate with given numbers, that how poor german ammo should be, to get 109 to perform right according williams data. 20mm german cannon is about 3-5 .50cals according to him. well, it might mean that only 1 of 50 HE ammo from german gun(20mm making 200mm wide holes) should work, to get in those numbers.   this just with target sheet and how big hole there becomes.

 

i believa that engine doesnt like if HE round explodes on its side, or bottom or top of it. its not just metal, but covered with fuel lines, oil lines, electricity lines, oil pump, gas pump etc etc. HE round in there would surely hurt a lots of parts, where AP round hurt only few. just look at P51 engine from side:

[Sternjaeger]

...erm, that's a valid point, but that's not a a real P-51...

and again, you have the risk of the round detonating on impact, not INSIDE the aircraft. It depends on the kind of fuze etc...

[BeastyBaiter]

well not really. Penetration in HE is also a determining factor, not to mention the angle of impact: when flying behind someone it wouldn't be uncommon to see some of the rounds bouncing off the enemy aircraft, kind of like when you skip stones on a lake.. We use a very simplified rendition as it is, let's at least ensure it's accurate.

 

True, I'm speaking in game but it is a rule of thumb for real life as well. There is also fragmentation to consider, which stafroty brought up above. Looking at an engine, an HE round could easily cause a fragment of metal from either the shell itself or from the plane's skin to sever electrical cords, rubber hoses and other soft items. The shockwave could also potentially cause a breakage if it was large enough. However, if we compare that to slapping an engine block with a 20mm projectile that will cut in one side and lodge itself halfway through it, I think it's safe to say AP is preferable. 1 cleaved open cylinder means the whole engine freezes right then and there. No limping, no coaxing it back to base, it stops more or less instantly and is beyond repair even if it does land safely. With HE severing some hoses/cables, you have a chance of starting a fire and are likely to kill a spark plug or two. An engine fire is a big deal obviously, knocking out a spark plug however is something you can work with. I've driven a car a good 5 miles with a failed spark plug. It was a rough ride, but I was able to limp to a shop. You can't do that with a siezed engine.

 

It is also true that a glancing impact may cause damage with an HE round and basically none with AP. I've even seen this in BoS with MG rounds bouncing off of planes when shooting from direct 6 at range. That is certainly a case where HE is preferable as it is almost certain to explode and do something (in game). IRL it is a little more complicated as the detonator must be triggered on an HE shell, so our game HE shells are probably a little overly effective in this extreme case. There are other ammo types as well, such as APHE. But I don't think we have any such things currently in game.

 

As for hitpoints, yes, they exist but not in a traditional fasion. From years of playing RoF and my experiences so far in BoS, the system seems to work like this:

 

1) A structural element, let's say a wing, has an overall stress limitation (combination of air resistance, G load and so on).

 

2) Each hit on that element reduces the overall stress limitation.

 

3) Not all hits are equal, calibre and ammo type have an effect.

 

4) There does seem to be a main spar modeled, damage to this part has far more effect than shooting other parts of the structure. In BoS, this part is resistant to rifle calibre MG's.

Edited June 23, 2014 by =LD=King_Hrothgar

[LLv34_Stafroty]

...erm, that's a valid point, but that's not a a real P-51...

and again, you have the risk of the round detonating on impact, not INSIDE the aircraft. It depends on the kind of fuze etc...

well, is that a model? heh, if it is, it fooled me. anyway, it shows still that there is more than just metal engine block.

 

of course. even delayed fuze can detonate on surface if it hits it at really high angle. so it kinda just cuts the skin without going under it, so delay fuze detonates it in there, just cause it hits it at high angle.

sure, there can be impact fuzes as well, which were not as effective, some countries did use them then switched to delayed ones, etc.

True, I'm speaking in game but it is a rule of thumb for real life as well. There is also fragmentation to consider, which stafroty brought up above. Looking at an engine, an HE round could easily cause a fragment of metal from either the shell itself or from the plane's skin to sever electrical cords, rubber hoses and other soft items. The shockwave could also potentially cause a breakage if it was large enough. However, if we compare that to slapping an engine block with a 20mm projectile that will cut in one side and lodge itself halfway through it, I think it's safe to say AP is preferable. 1 cleaved open cylinder means the whole engine freezes right then and there. No limping, no coaxing it back to base, it stops more or less instantly and is beyond repair even if it does land safely. With HE severing some hoses/cables, you have a chance of starting a fire and are likely to kill a spark plug or two. An engine fire is a big deal obviously, knocking out a spark plug however is something you can work with. I've driven a car a good 5 miles with a failed spark plug. It was a rough ride, but I was able to limp to a shop. You can't do that with a siezed engine.

 

It is also true that a glancing impact may cause damage with an HE round and basically none with AP. I've even seen this in BoS with MG rounds bouncing off of planes when shooting from direct 6 at range. That is certainly a case where HE is preferable as it is almost certain to explode and do something (in game). IRL it is a little more complicated as the detonator must be triggered on an HE shell, so our game HE shells are probably a little overly effective in this extreme case. There are other ammo types as well, such as APHE. But I don't think we have any such things currently in game.

 

As for hitpoints, yes, they exist but not in a traditional fasion. From years of playing RoF and my experiences so far in BoS, the system seems to work like this:

 

1) A structural element, let's say a wing, has an overall stress limitation (combination of air resistance, G load and so on).

 

2) Each hit on that element reduces the overall stress limitation.

 

3) Not all hits are equal, calibre and ammo type have an effect.

 

4) There does seem to be a main spar modeled, damage to this part has far more effect than shooting other parts of the structure. In BoS, this part is resistant to rifle calibre MG's.

good post. sounds good bout the damage modeling.

[HeavyCavalrySgt]

I am remembering stories about P-47s with jugs knocked completely off that kept running - as long as they were left at full power - long enough to go from France back to England.  Apparently it was a common enough occurrence that experienced pilots would tell new guys about it.

 

Thinking a bit about the comparisons: there is more going on with AP rounds than just poking holes in stuff.  There is a lot of heat created by a shell going through something that provides some resistance and they often make a jagged hole with a lot of spalling.  I don't have any experience with these small diameter cannon rounds, but I have looked at a lot of 105mm and 120mm sabot penetrations in armor.  The metal seems to flow (and spray) like water for an instant, then re-solidifies.  There are a lot of thermal effects inside the vehicles.  I expect that little cannon rounds hitting lighter structures would be similar.  

 

My thought is that AP rounds hitting structural members might not break it directly, but things like wing spars have a load on them and could be weakened and fail when they suddenly get a hole in them and a molten or softened area around the hole.

[pixelshader]

How many mg rounds you reckon for this hole? 

 

[LLv34_Flanker]

S!

 

 Pixelshader. 1 shot of 30mm HE Again to the topic. A 20mm HE shot can and will penetrate aircraft skin, it is not that thick. And generally more than one slam in to the same area thus going deeper into the structure trhough previous damage caused. I think the DM calculations can never be more than an assumption and hitboxes as we simply lack the computing power. IMHO the overall feel of a believeable DM is a good compromise over a hitpoint/health system we see in many games. At the moment BoS DM feels strange at times and devs saying a single 20mm will rip off a wing a bit dubious. Not even an Airacobra's 37mm did insta kills 100% of the time. Oh well, this topic is yet another endless threadnaught candidate

[Georgio]

Slightly off-topic but nonetheless relevant is the Air Ministry's insistence that air plane weapons be measured by pound weight per second to gauge effectiveness. This may of worked just fine circa WW1 when all that was stopping a bullet was some doped canvas but by WW2 the rifle calibre should have long gone the way of the Dodo.

 

I was always amazed that British planes didn't just stick in some .50 cals and actually do some damage...

[Dakpilot]

Slightly off-topic but nonetheless relevant is the Air Ministry's insistence that air plane weapons be measured by pound weight per second to gauge effectiveness. This may of worked just fine circa WW1 when all that was stopping a bullet was some doped canvas but by WW2 the rifle calibre should have long gone the way of the Dodo.

 

I was always amazed that British planes didn't just stick in some .50 cals and actually do some damage...

 

No, they went the 20mm route

 

Cheers Dakpilot

[LLv34_Stafroty]

 

I am remembering stories about P-47s with jugs knocked completely off that kept running - as long as they were left at full power - long enough to go from France back to England.  Apparently it was a common enough occurrence that experienced pilots would tell new guys about it.

 

Thinking a bit about the comparisons: there is more going on with AP rounds than just poking holes in stuff.  There is a lot of heat created by a shell going through something that provides some resistance and they often make a jagged hole with a lot of spalling.  I don't have any experience with these small diameter cannon rounds, but I have looked at a lot of 105mm and 120mm sabot penetrations in armor.  The metal seems to flow (and spray) like water for an instant, then re-solidifies.  There are a lot of thermal effects inside the vehicles.  I expect that little cannon rounds hitting lighter structures would be similar.  

 

My thought is that AP rounds hitting structural members might not break it directly, but things like wing spars have a load on them and could be weakened and fail when they suddenly get a hole in them and a molten or softened area around the hole.

yes, tank armor gets like that, its kinda is not molten because of heat it generated, but because of the really high pressure there is, thats the reason it "melts" and insta re-solidifies after round tip passed by, cos pressure eased.  There ls that flow like you mentioned, and sure it generates also rise of temperature in there too. Just not to point where armor steel would be molten in normal pressure. Penetration relies on that pressure with High speed hits like sabot and HEAT rounds. Sure the surface area of the tip which is in contact with armor gets quite hot, and makes that thermal effects, sparks etc.

 

but aluminium of plane is bit different thing. it is quite soft compared to armor steel.  So it doesnt resist the penetrating round much.

AP ammo mostly have their own incendiary agent in them, so one dont have to worry about heat issues it could created, as that will surely cause much more heat that penetration resistances could ever. Also heavier cal tracer burns quite long time, so if it hits something and stops the round, it might ieven detach that tracer element from that round. anyway, it might stay inside the stuctrure and burn there, and if it gets in contact with something like fuel, it will ignite it as well.  it burns hot as well and long duration, but if round goes thru intact tracer quite surely will go too.

 

getting hole in middle of structucal bar isnt too bad, it still can carry quite a load, but if it hits in its edge, that drops its carry capacity much more.

 

 

and about totally destroyed planes with barely made it over friendly territory, i think every side had those incidents.

[LLv34_Stafroty]

How many mg rounds you reckon for this hole? 

 

 

 

i strongly assume that the fuselage on that picture was shot at the cameras side. as this side the skin/structure is more devasted/thrown away, as well, there is flagment oles in this side skin material. At low sheets, in tail side of sheet and also in roof, but back sheets doesnt seem to have any, well perhaps there is one spot, which might be fuze parts hole at back side of that. In the middle of that hole, above it is a sheet which is almost in its place, it has that circular bend on its left side edge, as well sheet above it has its edge bent in same direction on that spot as well. just quessing.

 

i believe(not sure) that fuze was made from aluminium? just assume, can be steen too.. dunno. it is just quite big of a thing when compared to whole bullet, so it forms a biggest fragments from that shell anyway.

[LLv34_Stafroty]

i believe that vid has been here also before, but just wanted to post it. it can explain to some people, what difference there is in damage different ammunition/calibers are able to do, in terms of destroyed surface area..

 

 

http://www.youtube.com/watch?v=7Q4VuoX0Mqs

[BeastyBaiter]

Another interesting video of his: http://youtu.be/V8FzzEyegJQ

 

This one shows directly what a 20mm using a simple military ball round does to an engine.

[HeavyCavalrySgt]

 

 

but aluminium of plane is bit different thing. it is quite soft compared to armor steel.  So it doesnt resist the penetrating round much.

AP ammo mostly have their own incendiary agent in them, so one dont have to worry about heat issues it could created, as that will surely cause much more heat that penetration resistances could ever. Also heavier cal tracer burns quite long time, so if it hits something and stops the round, it might ieven detach that tracer element from that round. anyway, it might stay inside the stuctrure and burn there, and if it gets in contact with something like fuel, it will ignite it as well.  it burns hot as well and long duration, but if round goes thru intact tracer quite surely will go too.

 

 

 

 

 

 

I hope I didn't imply aircraft skin would be a hard target for AP rounds!

[LLv34_Stafroty]

I hope I didn't imply aircraft skin would be a hard target for AP rounds!

 

well, if that target would have been 5mm sheet of steel, light machine gun rounds and .50cal rounds as well cannon  AP ammo would have penetrated it easily.

especially 12.7 and 20mm AP. And this is where they shine against HE ammo. isnt it around 8mm what 7,62 ammo can penetrate with AP ammo from 100m distance?

again that thickness would be no problem to 12,7 or 20mm AP ammo. but i believe that HE or Mine ammo from  20mm-30mm ammo could do hole on it, at all.

 

against 5mm steel i believe mine ammo from 20mm would have made hole  around 15-20mm, roughly, this due fuze parts  of it speeding thru it cos of explosion behind it pushing it thru it. at least they do penetrate 3mm of steel. Dunno bout HE ammo, as it has less HE in it to give enough speed, dunno.

HE ammo has thicker steel body, in which inside is HE stuff, and fuze part in its "open end"so its BIT like a barrel,,   big assume that is, havent seen slow-mo from those, but i have seen 3mm thick sheet shot with 20mm HE-I ammo, which made holes on it about its caliber or even more. on 1mm steel holes were bout 10 times its caliber =20cm, didnt bother calculate. half that thickess steel holes were even bigger. twice as much.

 

 against 5mm steel fragments of 20mm mine ammo would not have penetrated it, as they would hit it at high angle, just ricocheting from its surface totally.

 

against 5mm steel 30mm mine ammo would perhaps do larger hole on it as it has quite big load of HE on it. perhaps size around 5-10cm cos of explosion force. If the explosion istn big enought the do it, then the size of the hole is around same what 20mm would do, due the possibility that they both had same size of fuzes. also fragments would not penetrate, or do almost anything to it from the shell walls of that ammo. (5mm steel)  (for this comparizon i believe it is easiest to compare nowadays attack chopper apache cannon ammo effects on that kinds of targets, even due its ammo is dual purpose. (high explosive bout 28-40 g and small shaped charge on its nose) having hollow charge on its front part means that the ammo is impact ammo, because hollow charge would be ineffective if it would not been, cos its copper cone would mushroom against the target before it  detonates, and that means it could not form jet of  copper hitting 2-5mm diameter area at high speed. If it flattens against target armor, it would mean that its just plate of copper(layer) against armor and behind it explosives detonates. copper flyes off without doing anything. that is why hollow charge ammo needs distance to target when they explode. that distance is quite important as well. it cant bee too short, nor it cant be too long.

[LLv34_Stafroty]

here is more about the issue. some of the threads get locked just because moderator feels that it is "necro" :D

 

 

http://forum.warthunder.com/index.php?/topic/154327-ap-vs-he-ammo-comparizoncalculations/

[LLv34_Stafroty]

i think the fuze if even smaller than 15mm on 20mm round. might be around 12-13mm

[SCG_Neun]

I've had this for a long time, maybe 10 years..but the information is good to review in graph form......I couldn't upload this format here.  refer to link:

 

http://www.simulatedaircombat.com/?q=node/83