WWII era Tank Gun Barrel Rounds...How do they work?

Modeling Subjects Armor
1

I feel a little silly[D)] asking this question, maybe I nodded off in Armor 101 class, but I need a lesson here…how does the mortar fired from the gun barrel, work to destroy the enemy tank? Yes, it’s a giant bullet, and I understand the propulsion portion, but what about from the time it leaves the barrel until it knocks out the enemy. Armor piercing, detonation, etc…I read about armor thickness and rounds penetrating this armor and blowing up the interior. Is the main purpose of the thicker armor to have the round detonate before reaching the interior, and ripping the steel versus rendering the tank, and its’ crew, harmless? Does the tip trigger the internal explosion? I assume the speed the round travels is so fast that detonation starts at impact but the momentum overcomes the speed it takes for the round to explode…always has puzzled me…can any of you ballistics guys help me out?

SMJ

2

Most of the AP shot in WW2 did not have HE filler, so when (if) it penetrated the armor it would primarily cause damage by bouncing around inside the tank and/or “falking” parts of the armor off and they, too, would act as shrapnel…HEAT rounds would cause a molten jet of steel to be shot into the tank when it hit, if it could penetrate—this is how the panzerfaust also worked (shaped charge)…

3

Early war AT rounds were solid metal, penetrate by brute force. If the round penetrates the cabin area there would be a rather nasty experiance for crew, molten metal from the armour be push by the shelf at a vary fast rate.

I am not to sure about later war AT rounds tho, does any one know when the hollow charge idea started to be used?

4

"Is the main purpose of the thicker armor to have the round detonate before reaching the interior, and ripping the steel versus rendering the tank, and its’ crew, harmless? "

No. AP rounds do not have a impact fuse (i.e. explosion when target is reached). AP rounds (as others have noted) defeated the enemy by puncturing the armor, not using chemical explosives to create an entry. Thick armor was meant to deflect or defeat penetration.

I don’t know when Allied rounds did this , but the Germans realized the need for a secondary explosion besides just the AP “solid shot” which was designed just to penetrate armor. They put a time delay fuze inside the warhead with a smallish amount of HE filler. Once the round would penetrate the armor, an instant later the fuze would initiate a secondary explosion.

As to the genesis of the hollow charge round, I dunno off the top of my head either. The first widespread battlefield introduction was the US M1 Bazooka. Captured by the Germans, they quickly adapted and improved on it – the Panzerschreck, raketenwerfer “Puppchen” and Panzerfaust series used the hollow round charge. The British PIAT was their version.

A note about hollow charge weapons: unlike traditional armor-piercing artillery rounds or bullets which depended on round velocity and hardness of the bullet/shell tip (i.e. kinetic energy), HEAT weapons just needed to hit their target at the right angle, regardless of impact velocity. The bazooka and german weapons were propelled by a crude rocket. The PIAT was fired from a spring loaded launcher.

Also unlike traditional AP rounds, the HEAT molten steel stream would only leave a tiny, dime -sized hole on the armor surface. Inside, the hole would be about a quarter diameter. The molten jet would be devastating for the internals (and crew). That’s why the angle of the HEAT warhead had to be correct for it to actually spew inside and do damage. Otherwise, it would just either fail to explode or spew harmlessly away.

5

T26E4,

A wealth of knowledge, as always, here on the forum. Funny though, my first thought sounds like it was correct…not what I posted in my thread. Just a big ol’ bad [censored] hunk of lead shot at break neck speed towards a moving hunk of armor!!! I think what threw me off was the interior compartment fires. The rattling around of the “lead”, is it really lead?, must have ricochetted around enough to hit something combustible, or cause the spark, or BOTH.

6

Some AP rounds have an HE filler that detonates after the penetration. If this occurs in exposed ammo, fuel, or other combustubles, secondary fires or explosions result. There is also another type of round used-HESH- High Explosive Squash Head. This round has a hollow nose and an explosive filler. It is designed to explode on the external armor and cause a “scab” of the armor to break off on the inside and ricochet around on the inside.

But basicly AT rounds break down into two catagories: 1, chemical energy- the filler in the shell uses chemical energy to burn through the armor; 2, kinetic energy- the projectile relies solely on its velocity and mass to penetrate the armor- energy imparted during the piercing is transferred to the armor pushed out of the way in the form of heat and motion.

7

When you see tanks that have been “brewed up” it’s usually because they were hit in either the fuel tanks or the ammunition storage or both and the resulting fires caused catastrophic damage. An AP round can cut electrical wiring, create sparks, etc. on its own sufficient enough to create an on-board fire. The Germans actually had a standard practice of continuing to fire on knocked out tanks, Shermans in particular, until they were set on fire to insure that they were total losses and couldn’t be recovered and put back into service.

8

As noted in the above posts, there are (generally) two types of WWII anti tank rounds. Armor Piercing, and Shaped charge. HE was designed for other stuff, but could be used to attack tanks.

Amor piercing is essentially a big hard chunk of something designed to punch a hole in the armor through brute force. Technically, this is kinetic energy that is tranfered to the target. Mass*velocity= energy. So the bigger the round and the faster it is moving, the more punch it has.

Shaped charge is chemical energy.

Throughout the war there was a race between the armor and the guns to see who was better. As the war went on the armor got thicker and the guns got bigger.

Armor: As you make it thicker, armor gets heavier, and the tank lose speed and manueverability. (think Ferdinand, JSII, etc.) But make it too thin and you are in trouble (think m10). But if you slope the armor the armor seems thicker to the incoming shot (it is angled like this / / which is a longer distance than | |.) (think T34 and Panther) Plus the slope increase the chances that the incoming shot will glance off rather than penetrate. Hence the emphasis on reducing vertical sides, ‘shot traps’ and other places that would snag the shot and allow the full power of the kinetic energy to be delivered to the armor. But essentially, you are just punching a hole in the target.

HE Shot: High Explosive shot is primarily for use against light vehicles and infantry. But a big enough HE round against a target can have bad effect on the enemy. The force of the explosion is dipersed equally in all directions (physics, again). But a big bang close to crew can stun them or knock out systems like radios, gyros, vision systems, etc. Plus it can stun or even kill the crew. Or it can cause spalling, where a chunk of metal on the inside of the tank flakes off and goes bouncing around inside the tank. Needless to say, this was very bad for the crew. But HE just does not get the job done against armor, all things being equal.

AP shot: Armor Piercing shot has to be going fast, be hard, and be heavy. It needs a lot of energy to penetrate all that armor. But physics being what it is, every action has an equal but opposite reaction. So the force sending the round down the barrel will also send recoil back the other way with the same energy (think of the recoil on howitzers, etc.) There are limits to how big a shell you can fire before the recoil overcomes the gun and the tank. There was a great deal of effort expended to make the shot travel faster. One way to do this is to more propellent, which needs a longer burn time, and a longer time in the barrell to accelerate. Hence the longer and longer barrels on guns as the war went on. But the limits of tank size and engine horsepower made it extremely difficult to put a big enough gun on a tank and yet allow it to remain mobile or have enough armor. (open topped tanks and assault guns are ways to put a bigger gun on the same size tank)

The other way to increase the energy delivered down range is to make the shot bigger. Hence the progression of 50MM to 75mm to 105MM, to 120MM, etc. But evetually the physics catch up with you and you must have a very big gun platform to handle the recoil, etc.

There were also efforts to make the penetrators harder. The Germans liked Tungsten for it’s excellent density and hardness, for example.

HEAT, or Shaped charges: Through another quirk of physics (the Bernoulli effect, I think), an explosive charge with one concave face (one side with a cone shaped hole in it) will create a jet of plasma (molten gases) traveling in the direction of the cone instead of just dispersing in all directions like normal HE. You get a higher percentage of the power of the HE being delivered to the side of the tank. When a shaped charge explodes on armor, that jet of plasma literally burns a hole through the armor. So you can take an HE shell and carve a cone in it and get ten times the killing power for no increase in tank or gun size. An excellent deal. But there are limits. The shaped charge needs to be a certain distance from the armor to form the plasma jet. Too close was bad, so HEAT rounds were designed to explode several inches away from the tank to give the jet space to form properly. But too far away was bad as well. That is why the Germans and other put skirts and sandbags etc on tanks. They made the shaped charges explode too far away, which did not allow the plasma jet to form effectively, essentially converting them into normal, ineffective HE rounds.

Effects: Once the tank was hit by a round, bad things could happen. Small penetrations by AP rounds could bounce around inside, killing the crew and starting fires. (the physics of this converts a lot of the energy involved in to heat, so the penetrating metal would be VERY hot once it got inside. This starts fires, which is why tanks ‘brew up’ (burn) after they are hit. Or the hot shot would hit something flammable or explosive. Like fuel or ammo. And this would be bad and cause the catastrophic loss of the vehicle. Of course, sometimes the shot would merely pass completely through the tank (read Enemy at the Gates, Craig)

But the plasma jet from a shaped charge would almost always cause bad things to happen. Which made them deadly and effective tank killers.

So fires and explosions inside the tank are caused by a jet of plasma at 2,000 degrees or a chunk of superheated metal (again, at very high temperatures) coming in contact with flammable stuff, like ammo, fuel, or the odd crew member.

There are many good sources for more detail on this, but this is what I remember off the top of my head. Read Man Against Tank by Weeks as an excellent resource on this topic)

(This arms race continues, of course. Depleted Uranium shells are just away of getting more mass into the same size gun, ceramic armor melts at a higher temperature this preventing the plasma jet from penetrating; reactive armor explodes when hit, thus disrupting the plasma jet, etc.)

Physics is the Latin of tank warfare. Understand the root language of physics and you will understand the history of the tank!

Professor DerOberst

9

Just to add to the above post- the sabot round- a smaller caliber high density solid projectile that has a light weight sleeve around it that allows it to fit a larger diameter gun barrel. The sleeve or “sabot” falls away after leaving the gun barrel leaving the dense high velocity penetrator to proceed to the target. These were initially developed late in WWII by the allies for use in the 17pr, 6 pdr, and 76mm tank guns. The smaller high density penetrator has a higher velocity and longer range than a standard solid AP round fired from the same caliber weapon.

10

Stik, you are correct.

There are also aerodynamic reasons to use Sabot rounds, as the optimal ratio of cross section and length to weight is not the same as the optimal ratio for making the round go down the barrel really fast. And no, I don’t understand any of that.

And aerodynamics are really important too, cause no matter how much Kinetic energy potential the round has, it does not matter if you miss the target or the target can reach you at longer range than you can reach him.

11

Just to clarify that, PIAT is a mortar, propelled in the normal manner by exploding propellant. The heavy spring was simple part of the firing mechanism, effectively a firing pin, and was so heavy in order to eat up a lot of the recoil.

NTM

12

To be correct, there are no armor piercing artillery rounds, tank rounds yes artillery no. The difference is velocity. Artillery rounds are much slower. Even today a 105mm HE artillery round will only give the crew a headache. There was a HEAT artillery round which was to be used for self defense of the artillery unit (though I would not want to be in that situation).

Tank rounds are crimpped and fly at 2 to 3 times the velocity of an artillery round. Less range than an artillery round but a lot more kenitic energy.

Not trying to confuse the question…just an old anal artilleryman throwing in his [2c].

Rounds Complete!!

13

You might have been out for a little too long, at least for 155mm rounds. M712 Copperhead is an offensive shaped charge round, M898 SADARM (Search and Destroy Armour) uses EFPs.

The Germans have their own anti-tank 155mm round, named “SMART-155”

Both infra-red and radar guided to find its target.

NTM

14

Manic

I’m not quite that old, I served from the mid 70s to the mid 90s but the reference I was making was to an artillery round in the direct fire mode.

Yes, I know the “copperhead” can destroy a tank. As I remember it is a shape charge type and by its size, can do damage. The smart 155 fires a small armor piercing shot once it has identified the tank.

The copperhead is early to mid 80s technology. the smart 155 is late 80s to early 90s technology.

Anyway…what I was getting at was in the DIRECT fire mode and somewhat same calibre, an artillery round is not a tank round. They were not designed to stop a tank in direct fire (except for the 105 HEAT and only for defense). It was not until the 80s when we had a round to destroy a tank unless you want to consider the 155 or 8" nuke rounds (now those were fun)!!. Let us also not forget the MLRS with AT bomblets!! All of these are in the indirect role. But…the question was around WWII…none of this existed. Artillery rounds were not designed as AT rounds.

Artillery is an indirect weapon. Direct fire is ONLY for defense of the battery. With todays tanks and their speed, I don’t think I would ever want to use the direct fire site on the howitzer. It is a definite advantage to the tank

Then there is the difference between a gun, howitzer and mortar…well thats another thread. Thanks Manic.

Rounds Complete!!

15

One of the nastier effects I’ve heard of, beyond the methods already listed here, was the intense amount of pressure built up inside the tank when an AP round penetrated the armour. Even if the round and the resulting shrapnel missed the crew and vital components, the intense, instantaneous amount of pressure built up inside when the round penetrated could easily kill the crew on it’s own. When crew did survive one of these attacks on their tank, there were many reports of said crew bleeding from the ears and eye sockets as the high pressure had destroyed many of their blood vessels.

Apparently a lot of tank ammo design has capitilized on these effects to this day, as many reports from the wars in Iraq have reported enemy tank crews were basically “exploded” within the tank when the hydrostatic shock from an AP basically ripped them to shreds.

16

OK, fair enough… But just to have the exception to the rule for WWII, the 25lbr field gun had a solid AP, and later an APBC round, as it was found to be the most potent anti-tank weapon in British service in the early war.

NTM

17

As I said in my previous, the difference between “gun” and “howitzer”.

That aside lets face facts large calibre may not kill but could screw up your whole day. I can remember firing an 8" SP in direct fire. We hit an old M48. It did not open the side up but flipped the tank on its side. If anyone was in that tank they would have had one hell of a headache.

Rounds Complete!!

18

Whoa! That must have been a sight to see!

I interviewed a German WW2 tank vet who said he lost one tank, a Pz IV, when a large calibre arty shell plummeted onto the hull roof between the driver and radioman’s hatches. It cracked through and imbedded into the transmission. Both the driver and radioman were killed. The veteran (TC) and the other two turret crewmen got out.

He had no idea what exactly the shell was or even what direction it came from. Such the vagaries of combat.

19

I worked on the bomb squad for years, and what you want to remember is the blast emanates from the explosive compound at right angles to the surface of said compound. This is how a shaped charge works, the cone is at a 45 degree angle when looked at from the side. The charge detonates, the blast for want of a better term “Meets” itself, and is forced into a jet. The distance from the surface is crucial because this jet has a short life and is only effective within a certain distance. The improved version has metal covering the cone shaped explosive, think coffee filter, which is turned into a molten slug with tremendous force. Ouch, This is capable of being directed quite accurately.