120mm vs 125mm

**Bill** · 13 Aug 04,, 15:47

With the exception of the gun mantle, all the red areas in your drawing are extremely heavily sloped, greatly increasing their protection. For the M-1A1HA and newer abrams, there is DU238 armor reinforcing the chobham, so they are extremely well protected considering the actual thickness of the armor itself.

It is EXTREMELY unlikely that any autocannon used by anyone could penetrate any of those frontal areas highlighted in red. Because of the sloping the same is true for RPG type weapons. Many M-1A1HAs were hit in those areas with 125mm fire and RPGs during ODS1, and failed to penetrate. In fact, i can't remember ever reading of any frontal penetration of an M-1A1HA in either of the last two wars in Iraq.

PS...the 'author' of that link is a US Army field grade officer that was responsible for writing AARs for the US Army after ODS. It is a safe bet that he knows more about tanks than the rest of us put together.

**OddBall** · 13 Aug 04,, 16:58

Originally Posted by M21Sniper

With the exception of the gun mantle, all the red areas in your drawing are extremely heavily sloped, greatly increasing their protection. For the M-1A1HA and newer abrams, there is DU238 armor reinforcing the chobham, so they are extremely well protected considering the actual thickness of the armor itself.

This matters little since modern sabots do not ricochet. Also note that the areas painted in red are not protected by chobham, with perhaps the exception of upper hull area that has 900mm RHA resistance against HEAT but only 190mm against KE.

It is EXTREMELY unlikely that any autocannon used by anyone could penetrate any of those frontal areas highlighted in red.

I never mentioned autocannons. Any Russian sabot 1976> can penetrate the red areas(in fact even some older rounds, but they have large chance of deflecting. Although if they deflect from hull they can hit the turret gap/gun mantle)

Because of the sloping the same is true for RPG type weapons.Many M-1A1HAs were hit in those areas with 125mm fire and RPGs during ODS1, and failed to penetrate. In fact, i can't remember ever reading of any frontal penetration of an M-1A1HA in either of the last two wars in Iraq.

You have seen actual battle reports that specifically said turret ring/upper hull/gun mantlet were hit? One thing I didn't mention in previous post that red areas are weak against KE penetrators, not HEAT. Green areas however are very well protected, as 2 Mavericks and M829A2 sabot couldn't penetrate them. Also the sabots Iraqis had were mostly old steel penetrators that have really poor penetration values and ricochet at far greater angles.

PS...the 'author' of that link is a US Army field grade officer that was responsible for writing AARs for the US Army after ODS. It is a safe bet that he knows more about tanks than the rest of us put together.

That may very well be the case but being US Army field grade officer does not make one expert of enemy armor values. I fail to see how he can say "I am convinced that the published/known armor values for Russian tanks are significantly mis-stated" after he said the rounds penetrated known weak areas such as turret ring and side hull, unless of course that report was cut from a larger one that included reported penetrations on other, more protected areas.

**Bill** · 13 Aug 04,, 17:13

"This matters little since modern sabots do not ricochet. Also note that the areas painted in red are not protected by chobham, with perhaps the exception of upper hull area that has 900mm RHA resistance against HEAT but only 190mm against KE."

So then what do you contend the armor is in the red areas that you claim are not protected by Chobham? There is no RHA anyhwere on an Abrams(with the exception of the steel encapsulation shell of the DU238 inserts) that i am aware of.

190mm vs KE would mean that even US 20mm APDSDU could penetrate those areas. The new APDSDU ammo has an unclassified penetration rating of around 220mm.

All projectiles can ricochet. Sabots are no exception. If the angle of the strike is such that the ogive of the projectile hits at a near paralell angle, you're almost guaranteed of a riccochet. modern sabots(at least US M829 series) still have an ogive, so there is still a chance for a ricochet(though they pack so much KE they'd still have plenty of overmatch left if they riccocheted into the tanks armor).

"You have seen actual battle reports that specifically said turret ring/upper hull/gun mantlet were hit? One thing I didn't mention in previous post that red areas are weak against KE penetrators, not HEAT. Green areas however are very well protected, as 2 Mavericks and M829A2 sabot couldn't penetrate them. Also the sabots Iraqis had were mostly old steel penetrators that have really poor penetration values and ricochet at far greater angles."

No, not specificly. However, there were so many incidents of 125mm and RPG hits on the frontal turret during both ODS and OIF that it is almost inevitable some of them were hit in the red areas. During TF-1/15s thunder run into bagdahd some M-1s were hit with literally dozens of RPGs and stayed in the fight. I can link to the actual US Army AAR if you'd like. It was one hell of a fight.

"That may very well be the case but being US Army field grade officer does not make one expert of enemy armor values. I fail to see how he can say "I am convinced that the published/known armor values for Russian tanks are significantly mis-stated" after he said the rounds penetrated known weak areas such as turret ring and side hull, unless of course that report was cut from a larger one that included reported penetrations on other, more protected areas."

Yes, that is a snippet of a larger report. The Author is a US TACOM(TAnk COMmand) officer and was in charge of the evalutation of the M-1/Iraqi tank performance in the gulf.
Can't remember his name off hand, but he definitely qualifies as an expert.

One other note: The EXACT composition and protection of the M-1 armor package(s) is still highly classified. We're kidding ourselves if we think we know for sure what any of it's KE/Chem ratings are precisely. 180mm(for instance) is just a guesstimate. The same is true for the Leopard II, and Challenger II. There is a lot of info for the m-1 armor scheme on the net, but there's a damned good chance that some of that data is deliberate mis-information.

**OddBall** · 13 Aug 04,, 17:50

Originally Posted by M21Sniper

So then what do you contend the armor is in the red areas that you claim are not protected by Chobham? There is no RHA anyhwere on an Abrams(with the exception of the steel encapsulation shell of the DU238 inserts) that i am aware of.

Well, for example the turret gap, it's obvious there is no chobham in there. Turret roof is known for having only steel plate and spall liner. There was also a pic of the gun mantlet of Abrams, it had only thin steel plates with empty space between them to offer minor protection for KE and good protection for HEAT(spaced armor).

190mm vs KE would mean that even US 20mm APDSDU could penetrate those areas. The new APDSDU ammo has an unclassified penetration rating of around 220mm.

Ok.

All projectiles can ricochet. Sabots are no exception. If the angle of the strike is such that the ogive of the projectile hits at a near paralell angle, you're almost guaranteed of a riccochet. modern sabots(at least US M829 series) still have an ogive, so there is still a chance for a ricochet(though they pack so much KE they'd still have plenty of overmatch left if they riccocheted into the tanks armor).

Modern sbots only ricochet at max of 4 degrees, while older ones with l/d ratio of 15:1 and smaller at 12-7 degrees. So it's really non-existant for modern sabots.

No, not specificly. However, there were so many incidents of 125mm and RPG hits on the frontal turret during both ODS and OIF that it is almost inevitable some of them were hit in the red areas.

Almost but not quite. Also RPG hits to red areas don't matter since only the KE resistance is weak. And their sabots were old steel rounds that other armies(like Finland) use for training.

During TF-1/15s thunder run into bagdahd some M-1s were hit with literally dozens of RPGs and stayed in the fight. I can link to the actual US Army AAR if you'd like. It was one hell of a fight.

Some were hit with RPGs and didn't say in the fight, but since the crew protection level on Abrams is really excellent there were no under armor KIAs AFAIK.

One other note: The EXACT composition and protection of the M-1 armor package(s) is still highly classified. We're kidding ourselves if we think we know for sure what any of it's KE/Chem ratings are precisely. 180mm(for instance) is just a guesstimate. The same is true for the Leopard II, and Challenger II. There is a lot of info for the m-1 armor scheme on the net, but there's a damned good chance that some of that data is deliberate mis-information.

I am using Paul Lakowski's estimates, they are known to be quite accurate(and respected by almost everyone except die-hard Russian armor fans) and for example in case of M1A1 his estimates have been pretty much spot on with the official ones.

**Bill** · 13 Aug 04,, 18:07

Paul is a good guy. I used to converse with him frequently at the old warships1 board. But i have to say, believe me, the man is not going to release classified data onto the internet. His estimates are good approxomations. I would be utterly stunned if there was not at least some deliberate disinformation in his figures.

For example, i have posted at times great detail on various sites about some US weapons systems that i was very familiar with thru first hand use. However, you can bet your last dollar that i was not 100% accurate wrt the actual performance of said weapons. This site is no exception. Sure, i know the EXACT range of the M-82A1 sniper rifle, and it is posted all over the internet(with amusingly large deviations from site to site)....but the public figure is not correct, nor is the one that i've stated in the past on various websites. I use the public figures because well, they're public...and i don't want to go to jail- or compromise our troops.

I'm sure you have intimate knowledge about your own tank or it's ammo that you'd not release on a message board either, correct?

**OddBall** · 13 Aug 04,, 18:42

I seriously doubt Paul pulled his values out of his hat, there's a lot of research, measurements and reports involved. The highest protection Abrams has against KE penetrators is on the front turret which have the chobham&heavy steel plates(and DU in later models). You can't put those heavy plates into whole front profile or the weight goes to the roof. If he reports upper hull is only 190mm, it's based on some hard facts(like climbing into the tank and measuring). I'd say the error marginal is quite small(you can have only so and so much protection in certain space and let's not forget that the weight must match).

I'm sure you have intimate knowledge about your own tank or it's ammo that you'd not release on a message board

either, correct?

Not really, no. I am involved in a project where I have told every bit of detail I know about my tank.

**Bill** · 13 Aug 04,, 19:40

SO much for OPSEC...

I've had a lot of discussions with Paul. I do not beleive him to be the sort that would endanger US troops by releasing classified data. The M-1s armor package and protection level is officially still classified.

BTW, just 'measuring the thickness' of the armor doesn't really do much, because composite armor is different layers of different materials(which you obviously know), so a total thickness of armor really won't tell you much.

I'm gonna try and get a hold of Paul and ask him about all this.

NOTE: I sent him an email.

**OddBall** · 13 Aug 04,, 19:48

BTW, just 'measuring the thickness' of the armor doesn't really do much, because composite armor is different layers of different materials(which you obviously know), so a total thickness of armor really won't tell you much.

It does for areas which do not have composite. Also even if any thin armor section does have composite, the error marginal is very small because the resistance values of the various materials used are more or less known.

**Bill** · 13 Aug 04,, 20:04

Sure, if you happen to know the exact order and type of material.

Ceramic, steel, titanium would have different effectiveness depending on the order it was layered.

**OddBall** · 13 Aug 04,, 21:13

My bad, I was looking at wrong numbers. Upper front hull is reported 350-490mm KE & 510-800mm HEAT and got very nice armor upgrade in M1A1(HA) and M1A2. The figures I posted before are for front 1/3 side hull. I feel so embarassed now, lol.

.

**OddBall** · 13 Aug 04,, 21:30

Or to say it in Internet language, I PWNED MYSELF!!!!111

**Bill** · 14 Aug 04,, 03:00

No biggie oddball, i've made PLENTY of mistakes myself when trying to recall all the myriad info i have learned over the years.

**Injecteer** · 01 Oct 04,, 16:24

hi

a kinda general question...

the term "chobham" refers to a special type of armor, rite?

also, we all know, that Challengers have chobham, M1 and Leo2 have that too.

the question is, does the "chobham" mean a very special composition and order of layers, or is it just a replacement for "sandwich"? and, for example, could the t80's armor plates, also having a layered sandwich structure, be refered to chobham ones?

thnx in advance

**axl** · 01 Oct 04,, 22:31

chobham is more or less a nichname of burlington armour. it is a theory that challenger has it and the propability is pretty high. tom clancy ones stated that the abrams is using it as well, but i would not go for it. and the leo2 is definitively not using it (germans have a patent for a special armour package used for the leo2).

if you talk about chobham, think about a special composition with different materials in a specific order. it might be some sort of sandwich, but that's more or less it.

regards
axl

www.kampfpanzer.de

**Kozzy** · 17 Oct 04,, 18:24

Originally Posted by riclcam

I don't believe it. There are to many intangibles that factor in to making a shot like that. If you have the story I would love to check it out. I will explain in detail at a later time why I feel that this is a myth.

It isn't a myth, it's well documented.

The Challenger was informed of an enemy T-62 by a forward observer and engaged it using a HESH round. I believe it was stopped and firing on a stationary target. I don't know if the crew used the GPS or the GAS to engage the target though.

Abrams made kills past 4000m, the distance limit on the M1A1's ballistic computer. They just stopped and used the GAS.