# MK108 impact on ground targets?



## wiking85 (Jul 31, 2015)

I know the Luftwaffe fielded Sturmböcke, which were heavily armored and armed fighters to bomber killing that featured two MK108s in the wings at a severe impact on performance. How about if it had been used against ground targets? Would the Mk108s have been useful against armored targets or was the HE impact mitigated by armor? 
https://en.wikipedia.org/wiki/MK_108_cannon


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## Kryten (Jul 31, 2015)

It would have been pretty effective against light armour like half tracks etc and transport echelons, but without developing an ap round I doubt it would be much use against tanks or sp's!


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## wiking85 (Jul 31, 2015)

Kryten said:


> It would have been pretty effective against light armour like half tracks etc and transport echelons, but without developing an ap round I doubt it would be much use against tanks or sp's!



Even against top or rear armor?


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## Shortround6 (Jul 31, 2015)

The idea of armor was pretty much to limit the effect of HE shells. 30mm armor was generally considered to the minimum threshold of "shell proof". That is minimum armor that would provide protection against 75mm *HE* ammo. Against thin (8-12mm?) and brittle (extra hard) armor small caliber HE might prove somewhat effective. 
The British didn't rely on HE from even a 5.5 in gun for Anti-tank work. Doctrine was to fire the 100lb HE shell with the fuse hole plugged by the transport plug and depend on kinetic energy to do the job. Given a turret hit the impact force could lift the turret out of the turret ring. 

Some things don't scale well and HE Blast effect on armor plate is one of them. Given a somewhat ductile armor you may just dent or score the surface rather than 'penetrate' or punch a hole out. If the rear or top armor is thin enough it may work, but with top armor on tanks going 16-25mm it is getting a bit dicey.


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## kool kitty89 (Jul 31, 2015)

I'd think the better option for disabling armored vehicles would be going for soft spots. You'd likely only temporarily put them out of commission or hinder effectiveness, but it's still useful. (HE or HEI shells damaging tracks, wheels, turret/gun mounting components, etc) I wonder how pure incendiary rounds much fare too. 30 mm mine shells could fit a LOT of filler and thermite incendiary can do a broad array of damage. (including welding components together or welding blobs of molten iron onto moving parts) Not sure how concentrated the impact would be or how much thermite would just splash. (other incendiaries are good for igniting things of course, but thermite has some broader applications) The low velocity might help, but it's still going to impact supersonic and likely spray most of the charge unless it hits a confined area like around the tracks.

I seem to recall some trouble with thermite incendiaries igniting at altitude, but this would be a non-issue for ground attack.


Normal HE shells would probably be useful against similar targets to the P-39's 37 mm cannon and the British Vicker's S.



Edit: this may be of interest too, a nice list of different MK 108 loadings (some experimental)
Komet weapons: MK 108 cannon


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## Shortround6 (Jul 31, 2015)

For a a reality check the 30mm mine shell carried around 85 grams of explosive, A British no 36 grenade carried 69 grams of Explosive. A German stick grenade (potato masher) had about 6 oz. or 177 grams. German tank hunters wrapped 6 extra charges around a central grenade to form a bundle charge of 42 oz . (1.42kg)







This worked when thrown on the engine decks of Russian tanks. This is also almost as much explosive as a 105 howitzer shell carried.

Or try the British No 73 Grenade.

https://en.wikipedia.org/wiki/No._73_Grenade


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## Kryten (Aug 1, 2015)

wiking85 said:


> Even against top or rear armor?



You would need an AP round to penetrate armour plate, the 30mm he round has very little explosive effect relative to a tank, blast effect is minimal and negated by the blast wave following the easiest path, ie, up and out, and the shrapnel is not heavy enough to carry enough KE to punch through plate, it will simply ricochet off, , even the top of a tank is enough to protect against those little 30mm shells!

Sure you might get lucky and pop a few on the engine louvres, possibly starting a fire below if you managed to rupture something with the splinters, but that's not a practical approach, the Stuka carries 2x37mm firing ap, the Hurricane iid 2x40mm firing ap, even that was not enough to guarantee a penetration from the sides, a rear attack was preferable!

Years ago I was present at Lark Hill when firing 30mm RARDEN, a considerably more powerful round, fired at old Fv432 carriers , he rounds just made an interesting light show and small scallops, AP however went straight through and out the other side!


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## wiking85 (Aug 1, 2015)

How did 30mm shells take down bomber armor then?


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## Greyman (Aug 1, 2015)

I don't think it had to in order to do its job.


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## davebender (Aug 1, 2015)

Might have been a good weapon on German APCs for use against soft targets. Similar in concept to Mk 19 automatic grenade launcher.


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## Shortround6 (Aug 1, 2015)

There were darn few bombers flying around with 12-25mm of armor (top armor on most tanks) 6-9mm being a lot more common. Also only certain parts of the bomber had armor. Like seat backs or a bulkhead behind the cockpit or ammo racks. The actual structure of the bomber was not armored. The control runs were not armored (bursting shell could cut rudder and/or elevator cables). the engines were seldom armored, (almost never if IL-2s are taken out). Fuel tanks were not _armored._ They were "protected" which was rather different. A multi layer bladder inside a sheet metal tank or a coating on the outside ( tank could be of other materials but not armor steel) that would swell up when it came in contact with gasoline and seal up rifle caliber holes (or fragment holes). Not effective against large caliber (12.7m and above) solid shot let alone HE shells bursting on tank surface or inside the fuel tank. 

MK 108 rounds did NOT "take down bomber armor". They removed parts of the bomber (sometimes major parts) from around the armor.

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## Shortround6 (Aug 1, 2015)

davebender said:


> Might have been a good weapon on German APCs for use against soft targets. Similar in concept to Mk 19 automatic grenade launcher.



The MK 108 in a ground mount is neither fish nor fowl. It weighs 58kg without a mount compared to the 35-36KG of the MK 19. The ammo is bulkier and heavier, the gun is going to have more recoil (putting a pair of spade grips on it and sticking it on pintle mount is probably not going to work). It also has over twice the muzzle velocity, which while helping direct fire shooting (provided the mount is stable enough to have the 2nd round land anywhere near the first),is going to make lobbing rounds into 'dead' ground (ravines, behind walls/buildings, etc) rather difficult.


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## stona (Aug 2, 2015)

kool kitty89 said:


> I'd think the better option for disabling armored vehicles would be going for soft spots.



Pilots did well to hit vehicular targets at all, never mind 'going for soft spots'.

Research by the RAF showed that a Typhoon firing 4 x 20mm cannon (a significantly greater rate of fire than 2 x MK 108s) could send an average of 120 rounds in the direction of a 10' square target, normal to the line of flight, in a typical attack. An average of 32 of these rounds hit the target.

Cheers

Steve

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## kool kitty89 (Aug 2, 2015)

stona said:


> Pilots did well to hit vehicular targets at all, never mind 'going for soft spots'.
> 
> Research by the RAF showed that a Typhoon firing 4 x 20mm cannon (a significantly greater rate of fire than 2 x MK 108s) could send an average of 120 rounds in the direction of a 10' square target, normal to the line of flight, in a typical attack. An average of 32 of these rounds hit the target.


Indeed, but there's still a difference between low angle attacks and steep diving attacks aiming primarily at the top surface. Granted, a tank's profile is a smaller target than its top, and there's other differences in vulnerability to ground fire between steep diving attacks and ones from astern at low level. (OTOH, to have sufficient pull-out time, you can't get very close in a steep attack or you need to limit dives to lower speeds, increasing vulnerability anyway)

And the MK 108 isn't that much heavier than the Mk. II Hispano (50 kg for the Mk. II I believe, with the Mk.I Hispano and French HS.404 -and American M1?- weighing 60 kg), so something like the Typhoon, Tempest, P-47, or possibly even Mustang, P-40, or Hurricane could have potentially mounted them. (possibly too bulky for the P-40 and Mustang, but they did manage to fit inside Fw 190 wings with some work, so maybe, but Ammunition was obviously heavier than hispano rounds) But there weren't any German fighter-bombers with wings of that sort around, and I'm not sure many twin engine ground attack aircraft using 4 MK 108s either, I think some Bf 110Gs did with 2 in the nose and 2 in a belly pack, not sure about Ju 88Cs. I wonder if a 4 MK 108s would have fit well on the Hs 129.


In any case, I'd be interested to know how thermite rounds fared against armor. Were thermite grenades and mortar shells effective in disabling tanks (more so than similar shells with HE filler)? German stick grenades were basically all concussion effect, so rather similar to mine shells (little srapnel unless lodged in a heavier body before exploding, not much from the thin casing itself)

If impact didn't splash the filler too much, thermite cannon shells might actually be effective at damaging upper surfaces of tanks and some other armored vehicles while potentially welding or fouling external moving parts. (I'd think a thermite shell hitting treads would more likely do disabling damage than a similarly sized explosive shell would)

Setting tanks on fire was also one of the more consistently effective ways of actually disabling/destroying them, so all around incendiary effect would be useful there. (but thermite, unlike flash incendiary mixtures, burns relatively slowly and with sustained white hot temperatures, producing molten iron masses or globules)


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## Shortround6 (Aug 3, 2015)

Please see; AN-M14 TH3 incendiary hand grenade

Thermate hand grenade. 26.5 of of 'filler' (751 grams ?), will "burn" through 1/2-inch homogeneous steel plate. 

or see video : Thermite Grenade Cuts Through Steel | Military.com

The MK 108 shells don't hold enough and obliviously a large majority of them would be subject to splashing the filler.


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## Kryten (Aug 3, 2015)

kool kitty89 said:


> Indeed, but there's still a difference between low angle attacks and steep diving attacks aiming primarily at the top surface. Granted, a tank's profile is a smaller target than its top, and there's other differences in vulnerability to ground fire between steep diving attacks and ones from astern at low level. (OTOH, to have sufficient pull-out time, you can't get very close in a steep attack or you need to limit dives to lower speeds, increasing vulnerability anyway)
> 
> And the MK 108 isn't that much heavier than the Mk. II Hispano (50 kg for the Mk. II I believe, with the Mk.I Hispano and French HS.404 -and American M1?- weighing 60 kg), so something like the Typhoon, Tempest, P-47, or possibly even Mustang, P-40, or Hurricane could have potentially mounted them. (possibly too bulky for the P-40 and Mustang, but they did manage to fit inside Fw 190 wings with some work, so maybe, but Ammunition was obviously heavier than hispano rounds) But there weren't any German fighter-bombers with wings of that sort around, and I'm not sure many twin engine ground attack aircraft using 4 MK 108s either, I think some Bf 110Gs did with 2 in the nose and 2 in a belly pack, not sure about Ju 88Cs. I wonder if a 4 MK 108s would have fit well on the Hs 129.
> 
> ...



Problem is gun attacks were made from low angle approaches, neither Stuka or Hurricane tank busters dived from steep angles, you came in low and walked your fire onto the target, even today A10's approach at a shallow dive angle.

Thermite would be utterly ineffective as pointed out in previous post, thermite has to be piled up in order to heat the steel high enough to melt through, nearly all the energy produced is lost to atmosphere, a cannon shell could not concentrate a large enough quantity even if it could place the thermite on target, which of course it could not, the thermite is travelling at the same speed as the shell, on impact and case rupture it would be sprayed all over the place!


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## drgondog (Aug 3, 2015)

Interesting discussion. I was project engineer on the Bell AH-J Seacobra for USMC performing an installation to replace the 7.62 mini gun in the Chin Turret with Colonel Chin's Wecom 30mm - a copy in most respects of the Mark 108.

AKAIK only HE was used as ammo - and the project failed because the firing frequency was too close to the airframe resonance frequency. I was up front with Major Kregaskis flying and both of us watching a TV monitor while flying a foot or so off the ground. after a second or two the deflections of the tail boom were Extremely noticeable. I shut it down immediately and we parked the bird at Yuma until we could look over the tail boom fittings and pylon mounts thoroughly. We left the gun at Yuma and came back to Euless without it. End of project, end of AT cannon on Cobra's - everything else was too big.

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## Balljoint (Aug 4, 2015)

Spalling was often an effective HE mechanism for defeating armor. Rather than penetrating the armor a shock wave(s) would travel through the armor and detach an interior armor surface –sort of like the suspended ball transfer of momentum. This was particularly effective against German armor later in the war when the toughening alloys i.e. tungsten molybdenum etc., were in short supply.


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## Shortround6 (Aug 4, 2015)

The British turned that idea into the "squash head" or HESH round but there are several very important details that prevent ordinary HE shells (or even mine shells) from acting that way. The explosive _has_ to be in contact with the armor and not spaced even a few inches away. This requires base fuses as opposed to nose fuses and requires proper timing of the fuse. Fuse acts too quick and the shell is still pretty much point on to the armor and most of the blast goes sideways. The fuse acts a little too slow ant the explosive is scattered all over the side of the tank. It also requires a shell body of the right construction and a HE filler of the right consistency. The shell body has to deform properly and the explosive has to have a putty like or plastic consistency in order to deform without fracturing or breaking into chunks. 

For tank vs tank ( or anti-tank gun vs tank) armored screens (or even tool boxes/ personal gear) can seriously degrade HESH performance if not out right defeat it.

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## bobbysocks (Aug 4, 2015)

squash head....is that a flat, blunt ended round...almost like a wad cutter? I remember seeing or reading about snipers during ww1 that went after the enemy snipers. they loaded their bullets into the casing backwards so the flat end was forward. snipers hid behind a steel plate but when that flat bullet hit the plate the shock wave would dislodge bits of steel from the other side and into the face of the sniper hiding behind it. so I can see how that same theory could hold in this instance.


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## Shortround6 (Aug 4, 2015)

The Squash head round is a special projectile, it may have a DP use as a substitute HE round but normal HE ammo cannot act like Squash head ammunition against armor.

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## wiking85 (Aug 5, 2015)

How about the impact on unarmored or lightly armored targets, like halftracks?


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## Kryten (Aug 5, 2015)

That would make a right mess if you dropped a couple in the top of a half track! 20mm firing ap-he at a far higher rate and velocity would be a more effective weapon though, 4 x MG151's for instance!

The problem with the 30mm is it has a trajectory like a rainbow, that makes range estimation far more critical, higher velocity rounds flying flatter would score more hits!


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## wiking85 (Aug 5, 2015)

Kryten said:


> That would make a right mess! 20mm firing ap-he at a far higher rate and velocity would be a more effective weapon though, 4 x MG151's for instance!


Would it in terms of destructive HE effect over twin 30mms?


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## Kryten (Aug 5, 2015)

He frag would be effective against infantry, but anything armoured, even lightly and you have a problem, little he rounds are not effective against armour, and the chances of a hit are lower with these weapons, and it's hard enough as it is!


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## wiking85 (Aug 5, 2015)

Kryten said:


> He frag would be effective against infantry, but anything armoured, even lightly and you have a problem, little he rounds are not effective against armour, and the chances of a hit are lower with these weapons, and it's hard enough as it is!



Well, looking at the HE contents the Mg151/20 had 18.6g HE and the 30mm Mk108 had 72g HE. As 20mm rounds could rip open a half track the much greater explosive content would destroy it. 
IDEAL WW2 FIGHTER ARMAMENT


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## wiking85 (Aug 5, 2015)

Shortround6 said:


> For a a reality check the 30mm mine shell carried around 85 grams of explosive, A British no 36 grenade carried 69 grams of Explosive. A German stick grenade (potato masher) had about 6 oz. or 177 grams. German tank hunters wrapped 6 extra charges around a central grenade to form a bundle charge of 42 oz . (1.42kg)
> 
> View attachment 297664
> 
> ...



The Mk108 rounds had 72 grams per round of HE. Several hits of that on engine deck armor should have an effect.

Some rounds had 85 grams:
Komet weapons: MK 108 cannon
https://en.wikipedia.org/wiki/Pentaerythritol_tetranitrate


> PETN is one of the most powerful explosive materials known, with a relative effectiveness factor of 1.66.[2]


with this explosive


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## Kryten (Aug 5, 2015)

wiking85 said:


> The Mk108 rounds had 72 grams per round of HE. Several hits of that on engine deck armor should have an effect.
> 
> Some rounds had 85 grams:
> Komet weapons: MK 108 cannon
> ...



I think you grossly overate the effect small amounts of HE has on armour, the whole point of armour is to prevent penetration by blast and fragments, and the whole point of AP rounds is to defeat armour plate.

They fired AP at armoured vehicles for a very good reason, as I mentioned above, I witnessed 30mm RARDEN fire hitting the side of an Fv432 and the sum total of the damage was a few scoops in the surface, the side of an Fv432 is less than half an inch thick, which was considered sufficient to stop small arms, HMG and shell fragments up to 122mm calibre, and a RARDEN has a much higher muzzle velocity than a Mk108!

72 grammes is not a lot of explosive, it's not going to worry an armoured vehicle much unless you get lucky as cause a fire!


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## wiking85 (Aug 5, 2015)

Kryten said:


> I think you grossly overate the effect small amounts of HE has on armour, the whole point of armour is to prevent penetration by blast and fragments, and the whole point of AP rounds is to defeat armour plate.
> 
> They fired AP at armoured vehicles for a very good reason, as I mentioned above, I witnessed 30mm RARDEN fire hitting the side of an Fv432 and the sum total of the damage was a few scoops in the surface, the side of an Fv432 is less than half an inch thick, and a RARDEN has a much higher muzzle velocity than a Mk108!
> 
> 72 grammes is not a lot of explosive, it's not going to worry an armoured vehicle much unless you get lucky as cause a fire!



72-85 grams of the most powerful explosive possible concentrated again a weak spot of armor in a round designed to cause not just armor penetration, but widespread structural failure in an aircraft. The whole point is to not use kinetic energy to breech armor, its using chemical energy to achieve armor breech:

_View: https://www.youtube.com/watch?v=ZoLLDi-M3fk_


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## Kryten (Aug 5, 2015)

I had a funny feeling that film would crop up!

Your comparing a thin aluminium wing skin, hollow inside the structure and no protective plate to an armoured vehicle designed to keep blast and fragments out, it's not remotely comparable!

Your arguing blowing up a bean tin is the same as punching through an anvil!

PETN is not the most explosive substance either, it's just one of a family of fillers!


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## wiking85 (Aug 5, 2015)

Kryten said:


> I had a funny feeling that film would crop up!
> 
> Your comparing a thin aluminium wing skin, hollow inside the structure and no protective plate to an armoured vehicle designed to keep blast and fragments out, it's not remotely comparable!
> 
> Your arguing blowing up a bean tin is the same as punching through an anvil!



Its also the tracer version of the HE round, not the most explosive of rounds. I take your point, but against 15-20mm of armor 85 grams of concentrated aimed/focused Hexagon (not a grenade layout where it disperses the blast effect) should be enough to breech it. The issue you are right about is getting hits with 2 vs. 4 guns, lower velocity, and lower rate of fire.


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## Kryten (Aug 5, 2015)

wiking85 said:


> Its also the tracer version of the HE round, not the most explosive of rounds. I take your point, but against 15-20mm of armor 85 grams of concentrated aimed/focused Hexagon (not a grenade layout where it disperses the blast effect) should be enough to breech it. The issue you are right about is getting hits with 2 vs. 4 guns, lower velocity, and lower rate of fire.



15mm-20mm of armour would only be breached by a shaped charge of that size, blast is a weird force, it always follows the easiest path unless you aim it, if they had developed a 30mm AP round there's no doubt that would be capable if disabling armoured vehicles, but plain old HE simply won't cut it.


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## wiking85 (Aug 5, 2015)

Kryten said:


> 15mm-20mm of armour would only be breached by a shaped charge of that size, blast is a weird force, it always follows the easiest path unless you aim it, if they had developed a 30mm AP round there's no doubt that would be capable if disabling armoured vehicles, but plain old HE simply won't cut it.



What are you basing that on?


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## Shortround6 (Aug 5, 2015)

wiking85 said:


> Its also the tracer version of the HE round, not the most explosive of rounds. I take your point, but against 15-20mm of armor 85 grams of concentrated aimed/focused Hexagon



What "aimed/focused" effect are you talking about? The German mine shell was no more aimed/focused than a Hand grenade was. 

The idea behind the German bundle charge was that ALL the grenade heads would go off at the same time ( or darn close) creating one big blast, not 2-10 little blasts spread out over time and distance. When dealing with explosives timing can be critical. PETN "burns" at 7-8,000 meters per second. TNT "burns" at 5,800m/s. A 1/2 dozen cannon shell hits, even in one second, are still 6 little distinct explosions and in no way comparable to the same amount of explosive going off "all at once". 

You can use Chemical energy to breech armor, you just need to use specialized shells/projectiles and not general purpose or simple high capacity HE rounds. Of course these specialized shells/projectiles don't work as well against non-armor targets. 

As far as using shaped charge projectiles from the MK 108 goes, Kyten has made a pretty good guess. Shaped charge penetration was advancing quite a bit during WW II so early performance was quickly improved but that advancement continued for quite a while after the war if not right up to today. What modern 30mm rounds can do bears no relation to what WW II rounds would do. Early (1940) shaped charges would not even penetrate a thickness of armor equal to their own diameter (and that is for an unspun projectile, spinning the projectile seriously degraded performance) while penetrations of 4 times the diameter were achieved in the 1950s in service ammunition and some rounds/war heads were heading for 7 diameters by 1960. Again, unspun. The spinning was such a problem that the French AMX 30 tank used a special double wall shell in it's 105mm cannon. The inner shell held the shaped charge and was separated from the outer shell by ball bearings, The outer shell revolved at high speed, the inner war head revolved much slower. The smaller diameter war head was traded off against the slower spin.


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## wiking85 (Aug 5, 2015)

Shortround6 said:


> What "aimed/focused" effect are you talking about? The German mine shell was no more aimed/focused than a Hand grenade was.
> 
> The idea behind the German bundle charge was that ALL the grenade heads would go off at the same time ( or darn close) creating one big blast, not 2-10 little blasts spread out over time and distance. When dealing with explosives timing can be critical. PETN "burns" at 7-8,000 meters per second. TNT "burns" at 5,800m/s. A 1/2 dozen cannon shell hits, even in one second, are still 6 little distinct explosions and in no way comparable to the same amount of explosive going off "all at once".
> 
> ...



Can you demonstrate that 75 grams of Hexagon explosive couldn't penetrate 15-20mm of armor?


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## Shortround6 (Aug 5, 2015)

wiking85 said:


> Can you demonstrate that 75 grams of Hexagon explosive couldn't penetrate 15-20mm of armor?



Can you demonstrate it can? and 15-20mm is a 33% increase in thickness. 






MK 108 mineshells have nose fuses. Shell will detonate after a _*very*_ short delay ( for use against aircraft you want the fuse to _initiate_ on the skin but detonate after several feet of travel so it explodes inside the aircraft instead of as it goes through the skin) not so good for armor penetration as shell may be splitting open when it detonates. Or instantaneous fuse detonates the explosive while it is pretty much still in the form of a cylinder that is end on to the armor (or angled) but then most of the blast goes sideways along the face of the armor. 

The 75 grams of Hexagon explosive will penetrate 20mm of armor if was arranged in a shaped charge and detonated at the right distance. in fact you need much less. 






27 grams of HE but then you don't get the blast effect against aircraft. See: http://www.ordnance.com/images/30mmHEDP1/30mmHEDP1 (4).JPG

And look at chart on the right hand side. The PEI-T round is not very effective against "heavy" armor but is more effective against everything else than the HEDP round. 

If HE shells alone would blow holes in moderately thick armor then people sure wasted a lot of time and effort designing/building AT rounds for a variety of cannon. 






Early HE ammo had 570 grams of explosive and later versions had 670 grams yet they designed and issued two different hollow charge rounds for this gun. The first would penetrate 45mm of armor at a 30 degree impact angle. (30 degrees from perpendicular). 

The 2nd of four different Hollow charge projectiles for the German 10.5cm howitzer used 2.12kg of cyclonite/TNT/Wax to penetrate 100mm at normal impact or 70mm at 30 degrees. The 3rd design penetrated about the same but used less explosive.

An awful lot depends on the arrangement of the explosive, the liner shape and material and the the fuse.


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## Greyman (Aug 5, 2015)

For what it's worth a 40-mm 'S' gun round (HE Mk.IIIT), 822 g with approx 90.5 grams TNT, 2310 fps - barely defeats 12-mm of HH armour, with a minority of fragments getting through.


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## kool kitty89 (Aug 5, 2015)

Were there any attempts at shaped charge 30 mm mine shell developments during the war?


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## GrauGeist (Aug 5, 2015)

Keep in mind that not all Mk108 shells were minengeschoss (M-shell), there was also the hydro-dynamic fused incendiary shell, too.


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## Shortround6 (Aug 6, 2015)

There were a few other types too. However at the time (WW II) a shaped charge 30mm shell was pretty much a waste of time. State of the art for shaped charges from rifled guns for service ammo in WW II was a penetration of about 1 diameter of the cone or just a bit better. Complicating this was that you need to detonate the charge at an appropriate distance. Too close and performance/penetration suffers. Many guns firing shaped charges did so at reduced velocities to limit the impact velocity and give the jet time to form/work with the stand off that the hollow nose cone provided. US 105 howitzer for example fired the HEAT projectile at 1250fpm instead of the 1550fpm the gun was capable of with full charge HE ammo. German Pak 75 could fire a Heat round at 450m/s compared to around 550M/S for HE and 790m/s for AP, both of which were heavier than the HEAT shell. Please note that they were trading the ability to hit (higher velocity means flatter trajectory and less lead on a moving target) for better penetration. 

Shaped charge ammo also needs a fair amount of _over_ penetration in order to achieve a good level of "lethalality". 

tank killing can be crudely expressed by the formula PK=PH x PP X PL or *P*robabilty of *K*ill = *P*robabilty of *H*it X *P*robabilty of *P*enetration X *P*robabilty of *L*ethal damage. 

Penetration by 75-105mm shot automatically gives a high PL due to the size, weight and speed of the "stuff" flying through the tank interior. Smaller AP rounds can have diminishing results. 7.9-14.5mm AT rifles can require multiple hits/penetrations in order to cause enough damage/casualties inside the tank to "kill" it. Shaped charges need a big enough "jet" to get through the armor to cause damage/casualties behind the armor. 

A picture showing a few variations.


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## Kryten (Aug 6, 2015)

wiking85 said:


> What are you basing that on?



seeing 30mm RARDEN actually hit less than half an inch of armour plate and fail to breach it!

and yet the 30mm apds went straight through both sides!

If you have no real life experience of this kind of weapon you probably think it's some kind of hugely destructive monster gun based on TV and games, in reality 30mm is quite underwhelming blast wise, it's the fragments that cause the real damage to unarmoured targets-


_View: https://www.youtube.com/watch?v=wewaCdSW4yc_

Bear in mind what your seeing there is modern high tech 40MM ammo, not WW2 primitive stuff!


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## Shortround6 (Aug 6, 2015)

I believe the the HE payload of the 40mm shell in the video is 120 grams of Octol.


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## GrauGeist (Aug 6, 2015)

For being "primitive", the 30mm round was about the deadliest airborn threat to anything with wings.


_View: https://www.youtube.com/watch?v=ZoLLDi-M3fk_

You can be sure that against soft targets on the ground: parked aircraft, vehicles, boats, structures or personnel, it will be devastating.

Against hard targets, such as medium/heavy tanks (for which it was not designed), it would make superficial damage but unlikely to breach the armor because, again, the 30mm minengeschoss round was not designed for anti-armor, but air-to-air engagement.


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## Koopernic (Aug 6, 2015)

I believe the Mk 108 30mm gun was actually quite good at getting a mobility kill. One Me 262 pilot (I'm sorry I can't remember but he was interviewed by a US museum curator) said he hosed the rear deck of tanks where the intake louvers for cooling the engine were. This is a big target. I can well imagine the blast, concussion and incendiary effect damaging an engine or at least bursting a radiator hose. In addition running gear, tracks, optics and external gun mounts could be damaged. A lot of tank kills probably were just mobility kills. It may have been quite good at this.


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## Kryten (Aug 6, 2015)

Koopernic said:


> I believe the Mk 108 30mm gun was actually quite good at getting a mobility kill. One Me 262 pilot (I'm sorry I can't remember but he was interviewed by a US museum curator) said he hosed the rear deck of tanks where the intake louvers for cooling the engine were. This is a big target. I can well imagine the blast, concussion and incendiary effect damaging an engine or at least bursting a radiator hose. In addition running gear, tracks, optics and external gun mounts could be damaged. A lot of tank kills probably were just mobility kills. It may have been quite good at this.



So how could they confirm the "mobility kill"? did the 262 stick around to check if anyone bailed out, or did he make a pass and get the hell out, did he hit the tank, compare the tank claims in Normandy to the real toll on vehicles and it all gets a bit doubtful.

These kind of anecdotes really are dubious and likely just that, anecdotes.


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## Shortround6 (Aug 6, 2015)

The German mine shell was certainly an interesting idea and extremely effective in certain circumstances. The Video of the Spitfire wing hit being an almost ideal target situation for the mine shell. A lot (comparatively) of explosive _inside_ a small _confined_ area/volume where the pressure from the blast can blow the skin panels from the framework and bend/distort ribs. A mine shell exploding in a much larger space (fuselage of 4 engine bomber) might not show quite the damage to both sides o(or both top and bottom). The Shells are still very dangerous.
The Germans _may_ have been the only ones who could make it in quantity during WW II. 
However _nobody_ has copied it for any purpose in the last 70 years which may tell us something also. 
A lot of ground guns have gone to dual feeds allowing the gunner to change types of ammo in 1-2 seconds (one belt of AP and 2nd of HE for example) and still nobody is using the HE mine shell.


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## wiking85 (Aug 6, 2015)

Shortround6 said:


> However _nobody_ has copied it for any purpose in the last 70 years which may tell us something also.
> A lot of ground guns have gone to dual feeds allowing the gunner to change types of ammo in 1-2 seconds (one belt of AP and 2nd of HE for example) and still nobody is using the HE mine shell.



Because technology advanced past it?


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## GrauGeist (Aug 6, 2015)

wiking85 said:


> Because technology advanced past it?


Because an ATA missile can achieve much better results at distances far greater than 690 meters...

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## Shortround6 (Aug 6, 2015)

The German Mine shell was intended for use against aircraft and for that it worked well. It is debatable as to wither it was the _best_ for that use or not, but it was a close race. It was certainly not the best for a number of other uses, anti tank or anti armor being one such use. With a large variety of targets that need to be dealt with you either put 3-4 different types of ammo in one belt hoping that 1/4 to 1/3 of the "proper shells' fired will be enough or you use general purpose shells that are not ideal for any one target but have moderately good results on most targets. 
Normal HE shells with thicker body walls and less HE throw more and larger fragments and have at least some effect at longer distances from the point of burst. Some countries (users) considered this an advantage, especially for troops in the open or behind light cover. It also allowed near misses (shell hits several feet away from vehicle/parked plane/small boat to at least damage the target with fragments. Nowhere near as good as the 40mm shell in the video but sort of the same effect on a reduced scale. The Mine shell was mostly blast with smaller fragments.

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## GrauGeist (Aug 6, 2015)

In all honesty, I think the closest to the Mk108 in use today, would be the GAU-8. This is not to say there is similarities between the two weapons, but the 30mm ordnance would be the link. The two main types of ammunition used in the GAU-8 (and varients) is:
PGU-14/B - Armor Piercing Incendiary (API - depleted Uranium)
*PGU-13/B - High explosive incendiary (HEI)*

It is the PGU-13 that would follow in the footsteps of the Minengeschoss round, as the characteristics and applications would be the very close.

Also, a close cousin to the Mk108, would be the mechanical version of the Mk103, the Mk101. In this 30mm weapon, there was a wide variety of ammunition available, including an AP round that was very capable of penetrating heavy armor. The drawback to the Mk101, was it's weight and slow RoF.


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## Shortround6 (Aug 6, 2015)

Actually the closest equivalent to the MK 108 is the M230 chain gun used in helicopters. 

The 30 X 113B ammo (3rd from right) is the closest equivalent to the 30 X 90 RB ammo (2nd from left) of the MK 108. 







It uses a lighter projectile at a higher velocity.

The 30 X 173 ammo used in the GUA-8 (3rd from right)is the modern equivalent of the 30 X 184 B ammo (1st on left in first picture) used in the MK 101/103






Photos from Tony Williams website: CANNON, MACHINE GUNS AND AMMUNITION


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## GrauGeist (Aug 7, 2015)

I suppose I should have clarified that I was speaking in terms of destructive yeild 

But good comparison in terms of relative size. I always wanted a collection like Tony's


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## Kryten (Aug 7, 2015)

I recall the DEFA and ADEN cannons were developments of the late war mauser rotary cannon, they initially used 30mm mine shells but in testing were found to be less effective than a heavier shell with higher velocity and more fragmentation, so the mine shell concept was dropped in favour of a lower filler capacity but greater fragmentation!

It would seem the mine shell was in reality a dead end and post war scientific testing discovered it's flaws, modern HE cannon shells are all about the fragmentation pattern and density, and far more effective than the mine shell concept.


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## wiking85 (Aug 7, 2015)

Kryten said:


> I recall the DEFA and ADEN cannons were developments of the late war mauser rotary cannon, they initially used 30mm mine shells but in testing were found to be less effective than a heavier shell with higher velocity and more fragmentation, so the mine shell concept was dropped in favour of a lower filler capacity but greater fragmentation!
> 
> It would seem the mine shell was in reality a dead end and post war scientific testing discovered it's flaws, modern HE cannon shells are all about the fragmentation pattern and density, and far more effective than the mine shell concept.



More effective for what?


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## Kryten (Aug 7, 2015)

wiking85 said:


> More effective for what?



destroying aircraft.

Did you notice the Bofors video was quick to point out the fragmentation effect and it's lethal radius, blast alone has a very limited radius , if the mine shells had been replaced with the kind of fragmentation shells used today the mk108 and it's smaller brethren would have been more effective.


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## Shortround6 (Aug 7, 2015)

To be fair the 40mm Bofors round uses a proximity fuse and the fuse and fragments turn what would be a miss with a contact fuse into a hit. I am not sure if anybody has managed to get proximity fuses down to the 30mm size. 

The early post war French and British revolver cannon used shorter cases and lower velocity but the low velocity was problem with getting hits. In addition to needing a high starting velocity you also need to retain velocity and light for their size (or frontal area) shells do not do this well. You can only trade shape (pointy nose) vs weight so much and long pointy noses may exceed the cartridge overall length the feed mechanism or gun mechanism allows.


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## Kryten (Aug 7, 2015)

I seem to recall ricochet was a major problem with the lighter rounds?


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## Koopernic (Aug 8, 2015)

kool kitty89 said:


> Were there any attempts at shaped charge 30 mm mine shell developments during the war?



One would expect they would be very effective, with a penetration equal to around the 30mm shells diameter. The shaped charges used in fracking are tiny yet they blow through a pipe and a meter of rock (the 'holed'razor sharp) these holes are then used for pumping through special polymer lubricated sands to fracture through around another 150ft.

The Germans developed a number of shaped charges for use on 75mm, 88mm and 105mm artillery. The main purpose seems to have been to give their low velocity indirect fire artillery and anti tank capability (including the recoilless canon they developed for their paratroopers) the "B" versions got to penetrations of around 1 diameter while the more advanced C versions close to 1.5 diameters from about 1943/44 onwards. Rounds had names such as:
Panzergranate 38 HL/B (PzGr. 38 HL/B) or Panzergranate 38 HL/C (PzGr. 38 HL/C) The HL stood for Hol Ladung or hollow charge.

The sleeve of these rounds was on a rotating bearing to reduce projectile spin as spin induces a centrifugal effect that reduces charge effectiveness so there may have been a loss in accuracy. A 30mm round might have good penetration though one wonders about its lethality, still it would be no fun if it went through the armour you were sitting next to.

Surprisingly these round were issued to high velocity guns, including those of the Tiger I and II.

These rounds were cost effective for short range engagements requiring less metal or propellant. It was German Army policy to keep firing into a tank till it was on fire and beyond recovery and repair and perhaps they were used for this.


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## Koopernic (Aug 8, 2015)

Kryten said:


> So how could they confirm the "mobility kill"? did the 262 stick around to check if anyone bailed out, or did he make a pass and get the hell out, did he hit the tank, compare the tank claims in Normandy to the real toll on vehicles and it all gets a bit doubtful.
> 
> These kind of anecdotes really are dubious and likely just that, anecdotes.



If the tank was on fire or smoking, that was an indication.

A British video of a single 30mm MK 103 mine shell test hit in a Spitfire wing at around the flap/aileron junctions shows the following effect:
The flap is blown off, the rear spar severed and a man sized hole has ripped up all the way to the main spar. In flight the wing would have failed.

A picture of a test against a Blenheim tail shows the tail blown open like a split watermelon to twice its size.

The concussive effects in the cooling intakes of a tank sure must have been signifcant and I can well imagine radiators split, fuel lines ripped, cooling lines destroyed.
The damage was likely repairable but the tank was stopped and that was often all that was needed.

Modern 'fragmentation' round often contain exotic technologies such as tungsten cubes.

Tank kill claims are likely exaggerations or really just mobility kills. The tank kill stats at Normandy show that getting a hit with a rocket was rare, very rare in combat but one can imagine the MK 108 being considerably more accurate and yet despite is low lethality if it did succeed in a hit since it was likely it could gain more hits it may have been quite effective if fired at the rear deck. It may have been more effective against thin skinned armoured vehicles such as half tracks than a rocket.

If used against thin skinned vehicles such as transports, tankers and repair vehicles the Mk 108 may have been an effective ground attack weapon. They were used to strafe and I have read of accounts of jeeps being attacked.


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## Koopernic (Aug 8, 2015)

Shortround6 said:


> To be fair the 40mm Bofors round uses a proximity fuse and the fuse and fragments turn what would be a miss with a contact fuse into a hit. I am not sure if anybody has managed to get proximity fuses down to the 30mm size.
> 
> The early post war French and British revolver cannon used shorter cases and lower velocity but the low velocity was problem with getting hits. In addition to needing a high starting velocity you also need to retain velocity and light for their size (or frontal area) shells do not do this well. You can only trade shape (pointy nose) vs weight so much and long pointy noses may exceed the cartridge overall length the feed mechanism or gun mechanism allows.



There is no problems with 'radar on a chip' so a 0.5 calibre round could have a radar proximity fuze. However the technique used by Oerlikon Contraves for its 35mm guns (now part of or rather back into the Rheinmetall fold) is to have a muzzle velocity measuring device and then to program the fuse with a time based on muzzle velocity measurement as it exits. The fragmentation pattern is sprayed forward by shaped charge and consists of small tungsten cubes which penetrate any missile. Guns are now more for terminal defence.

Not appreciated was that the Mk 108 gun and the mine round was very cost effective. Not only were only 3-4 hits required the round itself used very little metal (a high energy content material compared to explosives because of the refining and smelting costs) furthermore the casing was easy to make from sheet stock (probably cold drawn) and finally it could carry a self destruct to limit damage to the population down below.


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## kool kitty89 (Aug 8, 2015)

Mineshell type thin-walled HE projectiles were (are?) used in the British 30x113B ADEN ammunition, and I believe the French DEFA as well. Either it was drawn-steel similar to the German manufacturing method, or just very thin machined steel stock, either way the capacity seems similar to the German rounds, at least relative to the shorter, lighter projectiles.

International Ammunition Association {iaaforum.org} - View topic - 30x113mm Sectioned







PHOTO GALLERY 





The old 23 mm Madsen HE round also seems to be of a mineshell type construction, but again that might not entail using drawn steel cases but some other method allowing thin walls.


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## Kryten (Aug 9, 2015)

They adopted the mine round with the Mauser cannon, which is what the ADEN and DEFA are based on, post war testing found the rounds to not be as effective as anticipated, ricocheting off oblique targets and not producing the required destrucive effect.

The mine shell was changed for a heavier round , fired at a higher velocity with greater fragmentation, the mine concept was dropped and has not been used by any cannon manufacturer since!


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## Shortround6 (Aug 9, 2015)

Some of it depends on technology, and some depends on physics. Mine shells can work with a certain grade of steel and certain manufacturing process at a certain velocity. Shell walls have to be strong enough to take the pressure at the back end while supporting the heavy fuse in the front without buckling. This is harder to do with high velocity shells with larger powder charges (higher pressure) and usually requires thicker shell walls. If your fabricating and metal alloys are good enough you can use thinner walls at a higher velocity than someone else using cheaper metal and/or different shell body manufacturing techniques (including heat treatment). 
A lot of work was also done late war and post war to match the explosive to the specific shell body material (and processes) to optimize fragmentation. You need the right amount of brisance to the right material to get the size fragments you want. To much
Brisance can give you a few big pieces and lots of tiny pieces, shell body has literally shattered Too little and all you get is a few really big pieces and not many little ones, shell body has split open and vented the pressure before the body has had a chance to break up in the desired number of fragments. Tougher or more brittle shell bodies can be used with the same explosive to change the effect. 
Comparing ammo/shells from 10-30 years after WW II to WW II ammunition needs a lot of care as so many 'details' could have changed. Even (or especially?) things like fuses. British changed from a brass bodied fuse to an aluminium bodied fuse for 20mm Hispano ammo and saved around 14 grams of total shell weight (over 10%) which allowed for higher velocity with little or no change in operating pressure. Also no change in target effect as you could change fuses on existing ammunition( not sure it it was done but it was possible. )


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## Kryten (Aug 9, 2015)

What I have found interesting in modern design is how much attention is paid the fragmentation field density, it appears a larger number of smaller fragments in the envelope is the optimum for causing damage over a greater area, I'm also a little surprised just how far these fragments carry their energy!

I recall reading the late Gerry Bulls work on this, his 155mm artillery round produces something in the region of 3700 high energy fragments.


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## kool kitty89 (Aug 9, 2015)

Shorter shells of the same caliber would withstand higher velocities better, wouldn't they? (both due to the different dimensions -and particularly shorter overall straight-walled section- and the fact that the lower mass alone would allow for a velocity increase with a similar powder charge, though you'd really want a combination of shorter projectile and increased powder charge -which is more or less what the ADEN round did compared to the MK 108, with rather similar external dimensions and overall length of assembled cartridge, but a larger portion used by the case and propellant combined with a shorter, lighter projectile)

I'd think that more conical, tapered shells would be stronger on top of having superior ballistics. (plus they usually used more compact, lighter fuses and put less of the weight at the front of the projectile)


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