# HESH vs. HEAT



## BadEnoughDudeRescueRonny (11 Sep 2011)

What are the primary differences between HESH and HEAT ammunition? I know that HESH has the squash head that flattens to the target, but HEAT I'm a little more hazy with except for the fact that it delivers a shaped charge. Are there any differences beyond the fact that HEAT relies more on penetration through molten metal but HESH relies more on generating an explosive shockwave to neutralize a target? What would be some examples where HESH would excel and examples where HEAT would excel?


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## Franko (11 Sep 2011)

BadEnoughDude said:
			
		

> What are the primary differences between HESH and HEAT ammunition? I know that HESH has the squash head that flattens to the target, but HEAT I'm a little more hazy with except for the fact that it delivers a shaped charge. Are there any differences beyond the fact that HEAT relies more on penetration through molten metal but HESH relies more on generating an explosive shockwave to neutralize a target? What would be some examples where HESH would excel and examples where HEAT would excel?



Speaking from experience....

HESH is great at knocking a 5' hole in a grape hut and killing everything inside. Wiki is your friend-

http://en.wikipedia.org/wiki/High_explosive_squash_head



HEAT is great at killing everything behind a 1m thick wall and leave it mostly intact.

http://en.wikipedia.org/wiki/HEAT

In essence a HESH round is like taking a glob of silly putty and throwing it against a wall. It deforms and when the point detonator hit the surface it explodes sending shock waves and resulting in spalling.

A HEAT round has a piezoelectric fuze at the tip at a specific distance from the main charge. This is to ensure the jet is formed at the proper distance. When that is crushed it fires the explosive behind the shaped charge. The explosive wave crushes the metal (usually copper ) form into itself until it has nowhere else to go but towards the target as a molten jet of metal. This can burn through a few feet of anything that stands in front of it. The shaped copper shell is made to exact specifications to ensure the jet is formed and it goes where it is supposed to. 

HEAT rounds do not like rifled guns. It screws up the characteristics and ability of the round on impact. HESH needs the spin to ensure a good spread on impact.

There's alot more to it than that, but that's the basics.

Regards


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## vonGarvin (11 Sep 2011)

Der Panzerkommandant.... said:
			
		

> Speaking from experience....
> 
> HESH is great at knocking a 5' hole in a grape hut and killing everything inside. Wiki is your friend-
> 
> ...


I'm in Instructor in Gunnery, and I approve of this message 

;D

(Der Panzerkommandant said it better than I could)


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## BadEnoughDudeRescueRonny (11 Sep 2011)

Technoviking said:
			
		

> (Der Panzerkommandant *said it better than I could*)



    

The Technoviking has been bested?! Is that possible?! The Technoviking is a God amongst men whose boots can crush diamonds.


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## AmmoTech90 (11 Sep 2011)

Just one point, they are both base fuzed rather than nose or point fuzed.  HEAT is point initiated but base detonating and HESH is simply base detonating.


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## BadEnoughDudeRescueRonny (11 Sep 2011)

AmmoTech90 said:
			
		

> Just one point, they are both base fuzed rather than nose or point fuzed.  HEAT is point initiated but base detonating and HESH is simply base detonating.



Why is this fuzing system used? I'm going to guess, but is it to essentially direct the contents of the round out into the target?


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## AmmoTech90 (11 Sep 2011)

HESH- You need time for the projectile to pancake.  If the fuze was the first to hit the projectile would start to function while still impacting.  With a BD fuze, the fuze functions on deceleration so being at the back it should be the last to hit and slowdown and the projectile body should be well on its wasy to pancaking, add in the time for the fuze to function and all is good.

HEAT- As Der Panzerkommandant said you need a specific stand-off for HEAT to function properly.  However the explosive charge needs to be initiated from the bottom centre of the charge for the jet to form properly.  That is why you have the point initiation (to ensure proper time of functioning) and base detonation (to ensure proper method of functioning).  The is normally one of two means, electrical (piezo-electric crystals in the nose get crushed and produce current transmitted back to an electric detonator in the base), or explosive (crush detonator in the nose initiated detonating cord back to the base or spat back its own shaped charge to the base of the cone (older method)).  There are few HEAT rounds out there that do not use point initiation, but they are fairly rare.  The are a few designs out there that allow for firing from rifled barrels but they too are rare (fluted cone liners and ball bearing races to isolate the shaped charge are two methods).


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## BadEnoughDudeRescueRonny (11 Sep 2011)

AmmoTech90 said:
			
		

> HESH- You need time for the projectile to pancake.  If the fuze was the first to hit the projectile would start to function while still impacting.  With a BD fuze, the fuze functions on deceleration so being at the back it should be the last to hit and slowdown and the projectile body should be well on its wasy to pancaking, add in the time for the fuze to function and all is good.
> 
> HEAT- As Der Panzerkommandant said you need a specific stand-off for HEAT to function properly.  However the explosive charge needs to be initiated from the bottom centre of the charge for the jet to form properly.  That is why you have the point initiation (to ensure proper time of functioning) and base detonation (to ensure proper method of functioning).  The is normally one of two means, electrical (piezo-electric crystals in the nose get crushed and produce current transmitted back to an electric detonator in the base), or explosive (crush detonator in the nose initiated detonating cord back to the base or spat back its own shaped charge to the base of the cone (older method)).  There are few HEAT rounds out there that do not use point initiation, but they are fairly rare.  The are a few designs out there that allow for firing from rifled barrels but they too are rare (fluted cone liners and ball bearing races to isolate the shaped charge are two methods).



Once again, thank you for the great info!!!


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## Franko (11 Sep 2011)

Technoviking said:
			
		

> I'm in Instructor in Gunnery, and I approve of this message
> 
> ;D
> 
> (Der Panzerkommandant said it better than I could)



I've taught a wee bit of 105mm/ 120mm tank gunnery.     

Like I said, it's the basics. Ammo Tech90 pointed out the finer aspects.

Regards


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## Old Sweat (11 Sep 2011)

My sincere compliments to both of you for good, clear explanations. It brought back what I was taught on the IG Course in 1967, and indeed I was taught basically what you posted, including stand off distances (which was a function of calibre and hence cone size) and fuzing and all the rest. One question - does not HEAT also function better at lower velocities than one would expect from a tank gun? Something around 1000 - 1200 fps rings a bell, but . . . Come to think of it, that also applies to HESH, but it works at higher velocities.


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## AmmoTech90 (11 Sep 2011)

For HEAT Mv would affect the time available for the jet to form.  I guess that the faster you are moving the great the stand-off required, but given that VoD of the explosives used is usually greater than 7000m/s and results in a jet tip travelling at >>10,000 m/s the initial Mv would have to be a pretty good fraction of that to affect performance.

Mv definitely has an effect on HESH.  It has to be fast enough to pancake well, but not too fast that it smashes flat and gets spread too thin over too large an area to deliver the effect.


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## Old Sweat (11 Sep 2011)

Thanks. It's always good to hear from the real experts in a field. On reflection, I think the mv for HEAT issue was in relation to the 105mm How round, which was spin stabilized, and the effect of spin on performance has been discussed above. Mind you, I think the round was kept in stock for morale purposes, not for its effectiveness. It had a max penetration of about four inches and a trajectory like a beach ball.


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## Franko (11 Sep 2011)

AmmoTech90 said:
			
		

> For HEAT Mv would affect the time available for the jet to form.  I guess that the faster you are moving the great the stand-off required, but given that VoD of the explosives used is usually greater than 7000m/s and results in a jet tip travelling at >>10,000 m/s the initial Mv would have to be a pretty good fraction of that to affect performance.
> 
> Mv definitely has an effect on HESH.  It has to be fast enough to pancake well, but not too fast that it smashes flat and gets spread too thin over too large an area to deliver the effect.



732mps.


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## AmmoTech90 (11 Sep 2011)

I assume that you provided the Mv so we could figure out what impact a change of Mv would have on a HEAT round  >

Ok, so some simple math:

Lets say:
VoD is 8000 m/s
Length of charge (Lc)=20cm=0.2m
Time for charge to function (T)=?

V=Lc/T
8000=0.2/T
T=0.2/8000
T=0.000025 seconds is how long it takes for the explosive column to detonate completely.

Now we bump up the Mv to 1032 m/s (an increase of 300 m/s).  How much further forward is the projectile (this is important because it affects the stand-off and the overall penetration)
Same equation, d=Mv(T).  We'll use the delta of the Mvs to determine the difference in distance covered between the original and the new Mv.
d=300(0.000025)
d=0.0075m
so a difference of less than a cm.

Note that this is very simplistic and in no way is an accurate model because we have not incorporated how fast the fuze functions, which is not 8000 m/s and therefore would have a significant influence.  This assumes a truely instantaneous fuze.
Note that a modern detonator can function within 2.6 microseconds, so incorporating this would make a the total change in distance 1.5 cm.  As a more realistic example, the fuze in a 106mm HEAT projectile takes 10 microseconds to function (it is quite an old design).  This would mean a distance of:
d=300(0.000125)
d=0.0375 m or 3.75 cm.

And that kids, is why you need to know math. (Someone want to check it, please)  :nod:


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## vonGarvin (13 Sep 2011)

BadEnoughDude said:
			
		

> What are the primary differences between HESH and HEAT ammunition? I know that HESH has the squash head that flattens to the target, but HEAT I'm a little more hazy with except for the fact that it delivers a shaped charge. Are there any differences beyond the fact that HEAT relies more on penetration through molten metal but HESH relies more on generating an explosive shockwave to neutralize a target? What would be some examples where HESH would excel and examples where HEAT would excel?


To bring this back on the rails, I had a peek at the Wikipedia arcticle, and it give a good explanation.  I will paste it here, in case some 13 year old ninja surfer edits the page:



> High explosive squash head (HESH) is a type of explosive ammunition that is effective against buildings and is also used against tank armour. It was fielded chiefly by the British Army as the main explosive round of its main battle tanks during the Cold War. It was also used by other military forces, particularly those that acquired the early post-World War 2 British 105 mm Centurion tank, including Sweden, India, and Israel. In the United States, it is known as HEP, for "High Explosive, Plastic".
> 
> 
> HESH rounds are thin metal shells filled with plastic explosive and a delayed-action base fuse. The plastic explosive is "squashed" against the surface of the target on impact and spreads out to form a disc or "pat" of explosive. The base fuze detonates the explosive milliseconds later, creating a shock wave that, owing to its large surface area and direct contact with the target, is transmitted through the material. In the case of the metal armor of a tank the compression shock wave is conducted through the armour to the point where it reaches the metal/air interface (the hollow crew compartment), where some of the energy is reflected as a tension wave. At the point where the compression and tension waves intersect a high stress zone is created in the metal, causing pieces of steel to be projected off the interior wall at high velocity. This fragmentation by blast wave is known as spalling, with the fragments themselves known as spall. The spall travels through the interior of the vehicle at high velocity, killing or injuring the crew, damaging equipment, and/or igniting ammunition and fuel. Unlike high explosive anti-tank (HEAT) rounds which are shaped charge ammunition, HESH shells are not specifically designed to perforate the armour of main battle tanks. HESH shells rely instead on the transmission of the shock wave through the solid steel armour.
> ...



So, in short, it doesn't perforate the armour of vehicles by necessity.  The shock wave effect will cause the spalling, and this is negatively affected by the use of spaced armour, explosive reactive armour, and composites.  So, HESH is good against vehicles that have homogeneous armour, but not so good against more modern combat vehicles.

As well, HESH is awesome for its originally intended target: concrete.  It was by happenstance that it was found to work against armour.  


I hope this helps.


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## cupper (13 Sep 2011)

Someone pointed out earlier that HESH is effective against such structures as the common grape drying huts that were used by insurgents as redoubts.

Which type of ammo would be more effective against these types of structures, AP, HEAT or HESH, or do they each have their own advantage / disadvantage? Would one be more effective over the other in a direct fire vs indirect fire application (i.e. armd vs arty)?


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## McG (13 Sep 2011)

cupper said:
			
		

> Which type of ammo would be more effective against these types of structures, AP, HEAT or HESH, ...


Thermobaric.


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## vonGarvin (13 Sep 2011)

cupper said:
			
		

> Someone pointed out earlier that HESH is effective against such structures as the common grape drying huts that were used by insurgents as redoubts.
> 
> Which type of ammo would be more effective against these types of structures, AP, HEAT or HESH, or do they each have their own advantage / disadvantage? Would one be more effective over the other in a direct fire vs indirect fire application (i.e. armd vs arty)?


HESH would be best.  

HEAT is designed to perforate armour, and does so, as discussed, by focussing most of its energy at a focal point, backed up with a slug of molten metal.

AP would probably be the least effective.  These are hyper velocity rounds that are designed to perforate hard targets.  They are in effect really fast darts that punch tiny holes in things.  

You see, what you seek do to is after horrific "behind armour effects".  Against a cement structure, HESH is best of these three.  By far.

For artillery rounds, HE would be best (IMHO).  And it would work best against a grape hut if it detonated within the structure.  

But for your best bang, I would go with what MCG said: Thermobaric (they have heat and pressure effects.  "Heat" as in "temperature", not HEAT as in a type of round)


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## GnyHwy (13 Sep 2011)

Der Panzerkommandant.... said:
			
		

> Speaking from experience....
> 
> HESH is great at knocking a 5' hole in a grape hut and killing everything inside. Wiki is your friend-
> 
> ...



Der Panzerkommandant has already answered for HEAT and HESH a few posts above.  

AP will penetrate but will have very little behind armour effects (BAE).  Unless the target is directly behind the hole that the AP creates, they will likely survive.  There is something called a PELE round which is an AP round that produces very good BAE.  It's essentially a tungsten dart that is hollowed out and filled with plastic.  Once it penetrates, it shatters. Link here.

http://www.strategypage.com/htmw/htairw/20070619.aspx

For indirect fire, none of them are effective as they all require hitting the target to be effective.  Without a guidance system, conventional rounds are unlikely to directly hit the target.  With a guidance sytem it could conceivably be done with HEAT or HESH, but not likely and/or cost effective.  

Speaking strictly on AP and kinetic rounds.  AP's effectiveness depends on very high velocities.  To fire indirect with high velocities will create very long distances and long times of flight.  Again, with a guidance system, it is possible.  If you want to look at near and far future indirect projectiles, check out ram jets and scram jets.  Essentially a kamikaze guided projectile that will hit the target at extreme speeds over massive distances.  It doesn't need HE inside because it hits the target with such speed that its mass and velocity alone do the damage.


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## Colin Parkinson (14 Sep 2011)

As I recall one of the reasons we stopped using HESH/HEP was that we went to smoothbore, HESH needs some spin. They fixed this issue with a fin attachment if I recall correctly?

The 105mm C1/C2/C3 also had a HEP round, but never saw it live.


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## Franko (14 Sep 2011)

GnyHwy said:
			
		

> For indirect fire, none of them are effective as they all require hitting the target to be effective.  Without a guidance system, conventional rounds are unlikely to directly hit the target.  With a guidance sytem it could conceivably be done with HEAT or HESH, but not likely and/or cost effective.



Tanks can fire indirect up to 9-ish km. We have the technology and it's been around for a very long time.

We don't fire indirect very often....that's the artillery's job.      

Regards


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## a_majoor (14 Sep 2011)

Smoothbore weapons deliver rounds at much higher velocity, which would seriously affect the "squash" part of the HESH round. 

In principle, there is no reason a HESH round could not be made for a smooth bore cannon, but it would be fairly large and complex for the size of the warhead (needing pop out stabilizing fins), have a very low powered driving charge, and the ballistic computer and sights might have to be reprogrammed and modified to take into account the very slow flight time and "lobbing" trajectory.

Going the other way, the French actually made a HEAT round for use in their rifled cannons (the 105mm for the AMX-10RC armoured car and AMX-30 MBT), but this involved suspending the round on ball bearings and the driving band acting as the bearing race as the round went down the barrel. These rounds were not compatible with the 105mm L7 cannon either.

For the most part, HESH has been supplemented by such things as HEAT-MP rounds which have larger fragmentation effects and more behind armour effect, or enhanced HE like 84mm HEDP rounds for the Infantry. I also think (personal opinion) that the increasing use of compound armours negates much of the effect of the shockwave travelling through the armour plate and reduces the spalling effect inside the target, making HESH less effective these days. It is much harder to stop a KE penetrator or the hyper velocity "jet" of a HEAT round.

(Just as an aside, the jet of a HEAT round is moving at @ Mach 25, which is similar to the speed of a deorbiting projectile proposed in the THOR project. When you consider the damage a few ounces of metal moving at that speed can do, then scale it up to dozens or hundreds of kilograms [tactical THOR penetrators are supposed to be small, the size of broom handles, while the strategic ones that can penetrate missile silos and deep bunkers are indeed the size of telephone poles] the effects will be dramatic, to say the least).


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## PanaEng (19 Sep 2011)

The 84mm is a rifled weapon and fires a heat round - and yes, it uses a lubricating lining (teflon maybe) under the collar so that the projectile does not spin much in flight (if memory serves right) - a little spin is not bad  > 5k rpm (yes pulled out of my a$$) is probably bad.

Newer technology to counteract the effects of angular velocity include a liner with flanges or ribs or shock-wave guides on the interior of the projectile casing IOT create an opposite angular velocity to counter the one induced by the rifling. No sure if this is implemented in production rounds.

cheers,


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