High explosive vs. armor piercing rounds/guns

Discussion on the tanks and other armoured fighting vehicles, which participated in World War 2.

High explosive vs. armor piercing rounds/guns

Postby Blaster » Fri May 16, 2008 3:15 am

Do high explosive shells tend not to penetrate tank armor, and if so why? Also, why are armor piercing rounds inferior to HE rounds at bunker busting?
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Re: High explosive vs. armor piercing rounds/guns

Postby Notmi » Fri May 16, 2008 4:39 am

HE-shells contain much explosives and to get space for those explosive materials, shells are hollow and quite thinwalled. That hollow space is filled with HE. Being hollow their structure is weaker than solid shot structure. Hence they cannot be shot with high muzzle velocity which is a key feature on AP-shots. Then again, HE-shells dont withstand the stresses involved penetrating an armour and just break up. This is similar to high velocity problem.
Now, being slower velocity and weaker structure aren't the only reasons. One more reason is the weight. Steel density is about 8 grams / cubic centimeter while explosive density is around 2 grams / cubic centimeter (depending on explosive). Now this means that if you carve out say 4 kilograms of steel out of a shell and put explosives in place of steel, you can put fit only 1 kilogram of explosives. This leaves your shell 3 kilograms lighter than originally.
Now you have a HE-shell that is shot with lower velocity, is lighter and its structure is weaker than AP-shell structure. As higher velocity and higher weight (= higher kinetic energy) are essential to armour penetration, you can easily see why HE-shells are inferior in that.
Of course if you have large enough HE-shell, it probably will penetrate a thin tank armour.
(Disclaimer: not always were HE-shells lighter and with lower muzzle velocity than their AP-counterparts, especially when a gun wasn't high velocity gun. Also high velocity guns might have low capacity HE-shells with thick walls, shot with high velocity.)

AP shells are inferior to HE-shells in bunker busting because AP-shells dont contain much (if not at all) explosives. Bunker busting relies much on explosives, therefore HE-shells are more useful for that role than AP-shells.
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Re: High explosive vs. armor piercing rounds/guns

Postby Blaster » Sun May 18, 2008 1:58 am

I see.
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Re: High explosive vs. armor piercing rounds/guns

Postby canambridge » Sun May 18, 2008 9:49 pm

HE could destroy tanks in WWII, about 7% of US tank losses were attributed to HE. The number of damaged or disabled tanks due to HE was likely much higher. HE rounds do not tend to penetrate armor as explained above. But HE could damage or destroy a tank through other means, such as:
Concussion (over pressure), heat, shrapnel resulting in damage to critical equipment, such as track links, rollers, idlers, periscopes, range finders, and gun alignment. And very rarely through a piece of shrapnel penetrating the tank.

Crew effects: disorientation, temporary deafness, unconsciousness, even damage to internal organs.

Churned up ground resulting in bogging down of the tank.
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Re: High explosive vs. armor piercing rounds/guns

Postby Christian Ankerstjerne » Mon May 19, 2008 12:36 am

If the HE grenade was to hit the tank directly, it would also send a shockwave through the armour, causing metal fragments to be torn loose from the inside wall, flying through the fighting compartment. This effect was even perfected into a Cold War-era anti-tank grenade type, the HESH, though modern development in armour types has made this grenade type obsolete.
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Re: High explosive vs. armor piercing rounds/guns

Postby Ricky » Mon May 19, 2008 8:03 am

Heck, if your tank gets hit with a big enough HE shell then it will likely be disabled or destroyed. However, dedicated Anti-tank shells are more reliable...
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Re: High explosive vs. armor piercing rounds/guns

Postby siberian Black » Wed May 21, 2008 11:05 pm

IIRC some British tanks up to about the Gulf War retained the HESH shell capability. Is there something about HESH rounds that messes up the barrel or something?

Seems to me they would be fairly effective at bunker busting.
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Re: High explosive vs. armor piercing rounds/guns

Postby Christian Ankerstjerne » Thu May 22, 2008 7:20 pm

They are still used against bunkers in at least some countries, just not against other tanks.
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Re: High explosive vs. armor piercing rounds/guns

Postby Ricky » Fri May 23, 2008 7:55 am

British (and Indian) tanks still retain HESH ability. It is why we have rifled guns not smoothbores like everybody else.
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Re: High explosive vs. armor piercing rounds/guns

Postby siberian Black » Fri May 23, 2008 12:06 pm

So what makes a HESH round special that you need a rifled barrel for it?

Beside the fact that you can't really rely on velocity to provide accuracy if you want the warhead to work properly and not just make a pretty splat on the side of the target.
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Re: High explosive vs. armor piercing rounds/guns

Postby Christian Ankerstjerne » Fri May 23, 2008 1:19 pm

I would imagine accuracy. The main reason why the smoothbore has been introduced in tanks, is the fin-stabilised ammunition (e.g. APFSDS), since it gives a higher muzzle velocity.
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Re: High explosive vs. armor piercing rounds/guns

Postby Ricky » Fri May 23, 2008 1:58 pm

Just so we have it a third time - accuracy!

HESH (High Explosive Squash Head) works on the theory that when it hits the target it squashes into a 'cake' of HE that then detones, which creates shockwaves through the target's skin (armour, concrete, whatever) causing chunks to break off the inside. These chunks then whizz round smashing up any machinery or crew they hit. We still use them because they are a handy anti-armour weapon (only fails against the most modern armour) that doubles as a fortification-buster and trebles as a standard HE round.

But you can't fire them out of a smoothbore as they require spin-stabilisation.

Question - how do smoothbores fire HE with accuracy?
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Re: High explosive vs. armor piercing rounds/guns

Postby Christian Ankerstjerne » Sat May 24, 2008 3:13 pm

I would imagine they either don't need the same accuracy as AP ammunition, or they use fin stabilisation.
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Re: High explosive vs. armor piercing rounds/guns

Postby Blaster » Mon May 26, 2008 12:47 am

Ricky wrote:Just so we have it a third time - accuracy!

HESH (High Explosive Squash Head) works on the theory that when it hits the target it squashes into a 'cake' of HE that then detones, which creates shockwaves through the target's skin (armour, concrete, whatever) causing chunks to break off the inside. These chunks then whizz round smashing up any machinery or crew they hit. We still use them because they are a handy anti-armour weapon (only fails against the most modern armour) that doubles as a fortification-buster and trebles as a standard HE round.

But you can't fire them out of a smoothbore as they require spin-stabilisation.

Question - how do smoothbores fire HE with accuracy?


I was at the Calgary Stampede once and some Canadian soldiers were showing off a Leopard 1 tank. I asked them if smoothbore tank guns were less accurate than rifled guns, and they said the rifling in a tank gun was way bigger than rifle rifling-so big that it didn't really help the accuracy, since tank rounds were bigger as well. Then again I didn't specify the type of round so I dunno if this is true.
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Re: High explosive vs. armor piercing rounds/guns

Postby djconst2003 » Fri May 30, 2008 1:10 pm

The advantage of H.E.S.H. is that it is a dual purpose round, it can be used as an A.P. and H.E. round.
However it has to be said that British 76.2mm rounds had to be used carefully in the vicinity of bushes etc, and large flocks of birds.
It did a good job when used, whatever the target the round in the barrel did the job.

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