APFSDS projectile impact results


#1

I’m interested in learning more about what happens when the projectile from an APFSDS round hits a target. I understand the projectile is long and thin, pointed with fins at the rear, and is usually made of tungsten or depleted uranium. It’s my understanding that the tip and fins are not important for impact but rather for flight so they are often made of a lighter metal (aluminum?). The purpose of the tungsten or DU is for density and the high mass concentrated on a small area at high velocity allows superior armor penetration. Further, DU experiences adiabatic shear or so-called “self-sharpening” which makes it a better performer but tungsten is often used for environmental considerations. So that’s what I know (and please correct if anything is wrong or incomplete).
What I would like to know is what happens when this penetrator hits the target.
Let’s use multiple layers of metal plate as a reference target. What happens to the plate when the penetrator hits? How big are the entry and exit holes relative to the diameter of the penetrator? What happens to the penetrator as it travels through successive plates? Does the “tunnel” through the metal change diameter? What happens when it exits the other side? Are plate fragments or molten metal ejected? What happens to the penetrator (what condition is it in?) What happens to the tip and fins? Does the penetrator completely disappear or can you have an intact piece remaining? Now another case: what if the plates are too numerous to penetrate? Say the round can go through 10 plates but you have 15 or 20. What happens? Hole characteristics? Penetrator condition? Is material ejected forward (opposite direction of penetrator flight)?
After a firing and target strike and after the materials cool to ambient temperature, is everything melted together or can one remove the remains of the penetrator?
Apologies in advance for all the detailed questions but I realized how much I didn’t know when I tried to explain kinetic energy tank rounds to a friend and so I decided to come to the experts for an education.


#2

No expert here, but I was a tanker and have seen more than a few tanks knocked out by KE rounds. The hole made by the penetrator is not much larger than the diameter of the penetrator. As I understand it, the heat generated by the friction of the penetrator hitting the armor plate literally makes the armor liquify as the penetrator pushes through from sheer momentum. What happens on the other side is that molten metal sprays out of the exit hole into the tank’s interior causing all sorts of havoc. Obviously the penetrator will also destroy anything in it’s path, and often will go out the other side of the target. If it does not go out the other side, it will bounce around inside at high velocity making a mess… It was common for the KE rounds to go completely through Soviet model tanks during the Gulf War. Some M-1 A-1 tank crews claim that they could shoot through sand berms and still KO the tank on the other side!

During the Gulf War, our M-1 A-1s could engage Iraqi T-72s from beyond their effective range. Reportedly there was a very brief video clip on CNN during the war of an M-1 A-1 with what appeared to be the tail fins of a KE penetrator round sticking out of the front of the turret. I assume that this was fired as a “hail mary” shot by an Iraqi tank and did not have enough energy to defeat the armor. I looked through hours of video tape to find this, but never could confirm it.

AKMS


#3

Seems to me I saw that also. Looked like the Soviet Penatrator welded itself to the turret of the M-1.
Steve


#4

Interesting question! No expert myself but I don’t think the APFSDS speed is high enough to liquify the armor. Let me explain why. The HEAT projectile can penetrate armor by liquify it. The jet speed is almost 10.000 m/s at the top. This is more then enough to liquify the armor. But the jet slug following at 2000 m/s is often stuck in the small penetrated hole. Obviously 2000 m/s is not enough to liquify the armor. 120mm APFSDS has a velocity around 1700 m/s so to low to liquify the armor?


#5

Just a question and I don’t want to start an unholy row about this but is depleted uranium legal under international law?

The reason is I have recently seen references regarding an epidemic of childhood cancers and leukaemias in the area of GW1 said to be caused by the “illegal use of depleted uranium by coalition forces.”

It got me thinking.


#6

Hey Vince

Here’s a lengthy debate on the “legalities” of DU. There are other articles. This one seems the least emotional in its approach. Not a settled issue, by any means.

countercurrents.org/du-shah231004.htm


#7

Article…

fofanov.free.fr/Tanks/EQP/era.html

youtube.com/watch?v=v_-iXx6G_eo


#8

Article…
greatdreams.com/death/deathstar2.htm


#9

Nice to see someone else into APFSDS items. Here are a few pictures I have saved over the years that show some test plate APFSDS tests.

Jason

Israeli Test plate at a tank museum

105mm APFSDS test plate

Russian Test Plate

T72 Tank Turret hit by APFSDS penitrators

Not sure what projectile did this?

This was done by a HESH projectile


#10

The DU penetrator uses kenetic energy to penetrate the armor. The US 120 MM is moving at almost a mile a second.

"The sub-projectile’s hyper-velocity ensures that it strikes its target with devestating impact. By using very dense materials in the sub-projectile the stored kinetic energy is magnified greatly. The terminal effect of the sub-projectile striking the target sees huge kinetic energy release. In miliseconds the sub-projectile punches through the target armour, instantaneously generating massive heat and pressure. As the long rod penetrator enters the vehicle friction with the armour plate creates burning incandescent spall which sprays the interior. The burning spall has an explosive effect."Steve


#11

Jason,

Very impressive photos. Interesting how the HESH round seems to rupture large areas of the back side of the steel rather than just pierce it. Whole lot of energy goin’ on when it comes to poking holes in tanks!

Dave


#12

Yes the HESH causes “scabs” to come of the inside of the armor and fly around the inside of the tank. But this type of round along with HEAT and HE can be defeted with reactive armor.

Steve


#13

It definitely would suck big time to be on the receiving end for sure of these rounds. The latest greatest, US & German as well as a few others are so effective at armor penetration it is off the charts, especially the US M829E3 120mm APFSDS-T round. By far the most effective tank fired APFSDS-T round in the world, at least for now.

Jason


#14

Thanks for the replies so far. I want to steer this conversation away from a discussion of DU’s ethics. That is an interesting and important debate but one for another topic thread. This thread is focused on the technical aspects. Jason, thanks for the pictures of penetrated metal plate.

So we have some good discussion of the armor condition and results. Can someone discuss the condition of the penetrator (and some other unanswered questions from the original posting)?
A friend showed me a picture that is believed to be the remains of a 120mm penetrator. I don’t have a digital copy of it yet. But it is about 6 inches long by 3/4 inch diameter, dark brown to black, greatly disfigured with shear marks…frankly, it looks like a dried up and petrified dog turd. Could this be the remains of a penetrator?


#15

This is way outside my area but I did know some of the USAF people like Dale Davis, Steve Bilsbury and others who were associated with the development of the DU rounds for the GAU-8.

First, the story I have heard on why DU was used for the original A-10 rounds. The mission was to help stop the Soviet tank armies in Europe. The cartridges needed a penetrator that was very high density. During the design process, it was discovered that there were extremely large quantities of DU available in storage with very low radation levels so handling and storage was not a problem. The munitions guys use to handle DU projectiles just like any other projetical without any special provisions in the mid-1970 as I remember.

In addition to the KE effect of the very dense DU, There was considerable discussion about the Pyrophoric effect of the DU and that on impact, the tip of the penetrator burned with intense heat and actually burned it’s way through the armor in addition to the KE effect. I had never heard of this effect before and am only repeating what I heard from the people associated with the development of the round.

I use to have (and probably still do, somewhere in the boxes in the storeroom) a two inch thick piece of armor that has a hole through it from a GAU-8 DU projectile. As AKMS said, it is not very big (about twice the diameter of the DU penetrator. The flow lines on the exit side and splatter on the back of the plate sure look like there was molten metal flying around. I have been told that molten metal flying around the inside of the tank being hit is an important element of the kill mechanism.

I have not followed the DU arguments but Uranium, like most heavy metals is extremely toxic, particularly as a dust, quite independently of any radiation. You have to remember, that the round was developed to stop the Soviet Tank Armies, and if they were not stopped, then the battle would have gone nuclear. In that environment, there was not a lot of concern about the creation of toxic uranium dust from using DU projectiles.

Regarding AKMS’s comment about M-1A1s firing through sand berms, I was told by a fairly senior guy at Olin, just after DS/DS that just prior to the conflict, Olin had been delivering a new projectile and they had documented a case where an Iraqi tank drove behind a sand berm and the US tank crew, with one of the new projectiles had shot through the berm and destroyed the tank with a single shot.

Just random stories, but I have wondered if the titanium penetrators used in the later GAU-8 ammo was as effective as the DU. By that time I was years outside the aircraft munitions business and never had an opportunity to ask that question.


#16

[quote]Just a question and I don’t want to start an unholy row about this but is depleted uranium legal under international law?
The reason is I have recently seen references regarding an epidemic of childhood cancers and leukaemias in the area of GW1 said to be caused by the “illegal use of depleted uranium by coalition forces.”[/quote]

If I were a Kuwaiti or oppressed Iraqi, I would have chosen the use of D.U. munitions to remove Saddam’s forces, as opposed to waiting any greater length of time whilst the coalition came up with an alternative. Legal or not legal, everything is relative.

I have heard that there will be a seminar presentation at SLICS on Thursday night Concerning D.U. munitions. Should be interesting!


#17

Great information, Lew! Super interesting, especially coming from you. The round that was effectively fired threw the sand berm to kill the Soviet tank on the other side was the M829A1 120mm APFSDS-T round. This is also the same round the was supposedly shot threw one T72 and into another, killing both. In addition to just being a major buzz kill upon entering the tank, these DU long-rod penetrators in most cases actually ignite the stored ammunition in its target tank causing them to blow up, usually sending the tanks turret up and away from a few feet to 50 feet away from the tanks hull. The M829A1 has been replaced already by the M829A2 and now by the M829E3.

Jason


#18

Thanks for the discussion so far. Very interesting.

Here are some unanswered questions from the original posting. Hoping someone may shed some light on this:


#19

Viper,

If you look at picture #5 of the T-72 tank that was hit with the US APFSDS rounds you can also see the indents of the fins on the tank. I would imagine the fins sheered off or were compressed through the hole. As far as not penetrating, I dont know if thats happened yet in combat with the US 120mm. Even if it did not penetrate completly I would guess it would still throw Scabs off the other side of the armor. And the only way to avoid that is with spaced armor.
Steve


#20

You’re right, there probably has not been a combat case where the 120mm has been defeated. I was thinking more theoretical though. What would happen if it hit a stack of plates thicker than it could penetrate.