MK108 impact on ground targets?

[wiking85]

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

 

[Kryten]

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!

 

[wiking85]

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?

 

[Shortround6]

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.

 

[kool kitty89]

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

 

[Shortround6]

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

 

[Kryten]

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!

 

[wiking85]

How did 30mm shells take down bomber armor then?

 

[Greyman]

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

 

[davebender]

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

 

[Shortround6]

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.

 

[Shortround6]

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.

 

[stona]

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

 

[kool kitty89]

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)

 

[Shortround6]

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.

 

[Kryten]

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)

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!

 

[drgondog]

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.

 

[Balljoint]

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.

 

[Shortround6]

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.

 

[bobbysocks]

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.