Challenger II & Leclerc Armor for SB

[methos]

Unfortunately it doesn't seem to be that simple. In experiments conducted in a Dutch-Swiss cooperation (firing downscaled and full-size long-rod penetrator against a NERA sandwich and sloped steel plate), it was discovered that in some cases the depth of penetration into the sloped steel plate was increased by the interaction between the penetrator and the NERA sandwich. I.e. if the tip of the penetrator was bend downwards, the penetration into the steel plate was increased, even if the yaw had changed the flight path of the penetrator in such a way, that it would travel through a greater amount of steel armour. In other cases, the NERA failed to induce any yaw on the penetrator.

[Interlinked]

Unfortunately it doesn't seem to be that simple. In experiments conducted in a Dutch-Swiss cooperation (firing downscaled and full-size long-rod penetrator against a NERA sandwich and sloped steel plate), it was discovered that in some cases the depth of penetration into the sloped steel plate was increased by the interaction between the penetrator and the NERA sandwich. I.e. if the tip of the penetrator was bend downwards, the penetration into the steel plate was increased, even if the yaw had changed the flight path of the penetrator in such a way, that it would travel through a greater amount of steel armour. In other cases, the NERA failed to induce any yaw on the penetrator.

Yes, that's the catch. It's not so easy to get the rod to yaw very much or in the direction you want. That's why the guys who can make it work get paid the big bucks

[DB]

Very difficult topic, certainly. I speculate that a projectile that has yawed or been deformed by a complex array likely presents a very different tip shape/angle to a final protective or witness plate than an unaffected projectile would to a monolithic target at the same angle.

 

A projectile designer may manage deformation or ablation to improve the tip profile after array perforation before attacking base armour. Perhaps we see this with segmented penetrators?

[Paul Lakowski]

these arrays had 4-6 plates each with 1 diameter thickness and air-gaps of similar amount. It looked like multiple plates did yaw the projectiles reducing the overall penetration.

[methos]

Staff Requirement (Land) 4026 (Chieftain replacement aka Challenger 2) required 500 mm KE protection and 800 mm CE protection for the turret (at reduced frontal arc) and 350 mm KE and 650 mm CE protection for the hull.

 

Leopard 2A4 and M1A1 fell short of the turret requirement.

Edited October 24, 2023 by methos

[bojan]

So much about 800+ KE protection...

[Stuart Galbraith]

Is that saying the ability to defeated 700 RHA with L27?

Well wudja know, I was right after all....

 

What is the date of this document if you dont mind me asking?

[methos]

36 minutes ago, Stuart Galbraith said:

Is that saying the ability to defeated 700 RHA with L27?

No, it was the projected/required performance level for the CHARM3 program - not necessarily the penetration achieved with the L27. L27 entered service in 1999 as a result of the CHARM3 program; but the document is showing the performance requirements in ~1987.

Furthermore we already know that the UK had a tendency to measure performance of APFSDS rounds against highly sloped plates (i.e. it seems absolute plate thickness was always kept constant and heavier targets were simulated by increasing the slope and thus the effective thickness). However longrod penetrators are more efficient against highly sloped plates, inflating the penetration values. Don't forget that CHARM1 also was projected to achieve a penetration path length above 600 mm, while being inferior to M829A1 and DM43 in terms of actual performance.

Last but not least, British steel quality used to simulate Soviet tanks was extremely poor as mentioned in the documents posted by @Wiedzmin in the Main Gun Ammo topic:

The penetration against British steel plates was 18-22% higher than against German steel plates made to the TL 2350-0000 steel grade. So 700 mm against highly sloped British steel might be just ~588 mm against highly sloped TL steel and ~500 mm against unsloped TL steel.

[methos]

45 minutes ago, Stuart Galbraith said:

What is the date of this document if you dont mind me asking?

Should be ca. 1987/88. In late 1988/89, the idea of increasing the protection requirements (to 600/900 mm KE/CE for the turret) was discussed, but I don't know if it was ever implemented.

[Stuart Galbraith]

41 minutes ago, methos said:

No, it was the projected/required performance level for the CHARM3 program - not necessarily the penetration achieved with the L27. L27 entered service in 1999 as a result of the CHARM3 program; but the document is showing the performance requirements in ~1987.

Furthermore we already know that the UK had a tendency to measure performance of APFSDS rounds against highly sloped plates (i.e. it seems absolute plate thickness was always kept constant and heavier targets were simulated by increasing the slope and thus the effective thickness). However longrod penetrators are more efficient against highly sloped plates, inflating the penetration values. Don't forget that CHARM1 also was projected to achieve a penetration path length above 600 mm, while being inferior to M829A1 and DM43 in terms of actual performance.

Last but not least, British steel quality used to simulate Soviet tanks was extremely poor as mentioned in the documents posted by @Wiedzmin in the Main Gun Ammo topic:

The penetration against British steel plates was 18-22% higher than against German steel plates made to the TL 2350-0000 steel grade. So 700 mm against highly sloped British steel might be just ~588 mm against highly sloped TL steel and ~500 mm against unsloped TL steel.

Ah, so I get your point, this is setting the requirements, not necessarily saying they have been achieved. Have we any grounds for believing that the criteria, however it is calculated, was not achieved? If it wasnt 700rha by anyone elses, presumably it must have been according to the MOD's own, or Challenger 2 would probably have been looked at being rejected. It was already having issues with its fire control bu 1996,so it was already in trouble.

Im constantly amazed that there wasnt a commonly agreed NATO standard target which they based ammunition performance on. But then I guess it did allow various nations to massage data for the export market.

Edited October 24, 2023 by Stuart Galbraith

[Stuart Galbraith]

39 minutes ago, methos said:

Should be ca. 1987/88. In late 1988/89, the idea of increasing the protection requirements (to 600/900 mm KE/CE for the turret) was discussed, but I don't know if it was ever implemented.

Thanks for that.

[Ssnake]

2 hours ago, bojan said:

So much about 800+ KE protection...

We'll reassess, and adapt where necessary. Like we always did. When you have a lot of conflicting information floating around and a fixed release date, eventually you have to settle on something. We've downrated the Leopard 2A4 in recent updates, if you need an indicator about my degree of my emotional investment in armor protection estimation figures.

[bojan]

It was not a jab toward SB (which can realistically only use what is generally available info...), but toward general "C2 is super duper protected" narrative.

PS. Does Leo 1 in SB still has 300+mm KE protection on it's mantlet?

Edited October 24, 2023 by bojan

[methos]

1 hour ago, Stuart Galbraith said:

Ah, so I get your point, this is setting the requirements, not necessarily saying they have been achieved. Have we any grounds for believing that the criteria, however it is calculated, was not achieved? If it wasnt 700rha by anyone elses, presumably it must have been according to the MOD's own, or Challenger 2 would probably have been looked at being rejected. It was already having issues with its fire control bu 1996,so it was already in trouble.

Well, CR2 was selected in December 1988, the decision to buy it was made in 1991 and the first tanks were delivered in 1994. With the L27 entering service only in 1999, I don't think that its actual performance was any sort of deciding factor for the CR2 purchase.

As for whether the L27 met the requirements, I don't know. The CR2 design fell short of the requirements in a few aspects, but was still chosen due to the other candidates (Leopard 2, M1 Abrams and - with a lot less chances of being adopted - Leclerc) also fell short of some requirements.

It is worth noting that the penetration is listed in RHAE, so as RHA equivalent penetration and not necessarily as penetration into RHA. It might be the performance against a certain multi-layered/special target, maybe even protected with heavy ERA. We know that M829A1 at least had quite a lot of troubles with heavy ERA. Or it might be the penetration against steel - I have too little informations to make a judgement.

However based on the declassified report assessing the Leopard 2A4's improved protection posted by Wiedzmin in another topic, I don't have too much confidence in the British values from this time being too accurate. I.e. the Leopard 2A4's protection estimate is based on witnessing trials of the Leopard 2A4 stopping the 120 mm DM23 APFSDS and the German representative stating that this APFSDS round penetrates 400 mm. Because the armor stopped the round (in most places) over the 60° frontal arc with just slight bulges on the backside, they put the estimated protection at 410-420 mm vs KE.

In above document, they seemingly have decided to reduce the frontal arc to match CR1's protection of 435 mm vs KE. There wasn't any sort of conversion for different steel quality and penetration criteria.

[Ssnake]

3 hours ago, bojan said:

PS. Does Leo 1 in SB still has 300+mm KE protection on it's mantlet?

Short answer: I don't know

 

Medium answer: I use a Steel Beasts version that gives me detailed info about how much energy from the impacting round is lost at each stage of layer perforation, and from that I could work backwards to see to how much it accumulates until the round reaches the crew compartment (but I don't because I don't have the patience for that).

 

Long answer: While I could demand access to all the different armor files for direct inspection, I don't, for ... reasons.

That being said, I ran a few tests with 1970s and early 1980s 115mm ammunition, and in the end, no matter what the numbers are, the results appear plausible to me. While it usually took more than one hit to kill a Leopard 1A5 at 1500...2000m range (beyond that range, shooting becomes difficult because the targetting optics aren't so great for long range engagements), there were no hits that didn't result in crew, or severe component damage except for extremely lucky glancing shots.

I've invested about as much time to this question as I feel it deserves. The numbers are one thing, the more interesting question is out to which range the Leopard 1 can expect to survive hits by certain munitions (mostly in the 100...115mm range), and we can see a race between 1960s 115mm ammo and Leo 1 armor until the early 1980s, when both reached their peak. 1980s 115mm ammo largely wins over the Leopard 1. If you put a 1980s Leopard in the way of 1960s ammo, it has much better chances (duh).

[bojan]

2 hours ago, Ssnake said:

...If you put a 1980s Leopard in the way of 1960s ammo, it has much better chances (duh).

Yes, but no.  We had official German schematics about vulnerability of Leo 1 posted previously, apparently add-on armor did reduce 115mm APFSDS vulnerability... from 3500+m to ~2500m. Which is not really relevant, because as you have noted, T-62 never got FCS that enabled it to exploit such ranges, even M upgrade being limited to sub 2.5km in practice.

Edited October 24, 2023 by bojan

[Stuart Galbraith]

14 hours ago, methos said:

Well, CR2 was selected in December 1988, the decision to buy it was made in 1991 and the first tanks were delivered in 1994. With the L27 entering service only in 1999, I don't think that its actual performance was any sort of deciding factor for the CR2 purchase.

As for whether the L27 met the requirements, I don't know. The CR2 design fell short of the requirements in a few aspects, but was still chosen due to the other candidates (Leopard 2, M1 Abrams and - with a lot less chances of being adopted - Leclerc) also fell short of some requirements.

It is worth noting that the penetration is listed in RHAE, so as RHA equivalent penetration and not necessarily as penetration into RHA. It might be the performance against a certain multi-layered/special target, maybe even protected with heavy ERA. We know that M829A1 at least had quite a lot of troubles with heavy ERA. Or it might be the penetration against steel - I have too little informations to make a judgement.

However based on the declassified report assessing the Leopard 2A4's improved protection posted by Wiedzmin in another topic, I don't have too much confidence in the British values from this time being too accurate. I.e. the Leopard 2A4's protection estimate is based on witnessing trials of the Leopard 2A4 stopping the 120 mm DM23 APFSDS and the German representative stating that this APFSDS round penetrates 400 mm. Because the armor stopped the round (in most places) over the 60° frontal arc with just slight bulges on the backside, they put the estimated protection at 410-420 mm vs KE.

In above document, they seemingly have decided to reduce the frontal arc to match CR1's protection of 435 mm vs KE. There wasn't any sort of conversion for different steel quality and penetration criteria.

They were testing it for several years though weren they? And the first tanks only entered service in 2000. They were held up for 4 years with the fire control problem. The ones that entered service in 1996 were a trial production batch IIRC. So by the time the final decision was made for it to enter service , they would already have been firing prototypes of L27.

None of this proves it achieved the general staff requirements, but it does suggest that it must have  come at least somewhere near. After Challenger 1's problems, there was a powerful political lobby to buy abroad, as you will doubtless see in the Haynes book which does a large chunk of a chapter on it. If there was a considerable disparity in performance, it would have been a powerful case to knock it on the head, particularly considering the period when, then as now, we were considerably cash strapped.

Is there any explanation of how it was projected to perform better than the smoothbore APFSDS rounds, or were they just downgrading them to make XL30 firing XL27 look like it was going to perform considerably better? Which is odd in itself,  because the Army seemed to actually want Abrams.

[Ssnake]

9 hours ago, bojan said:

Yes, but no.

As I hinted, even with older ammo there were next to no hits that didn't cause damage, including crew loss. In that sense it's meaningless if there is an overestimate with certain numbers, as long as the simulation still delivers adequate results.

[methos]

3 hours ago, Stuart Galbraith said:

They were testing it for several years though weren they? And the first tanks only entered service in 2000. They were held up for 4 years with the fire control problem. The ones that entered service in 1996 were a trial production batch IIRC. So by the time the final decision was made for it to enter service , they would already have been firing prototypes of L27.

The Challenger 2 entered service in June 1998, not in 2000. The first trial batch entered service in 1994. So the CR2 is pre-dating the L27A1. While obviously L27A1 could not enter service before the first Challenger 2, it could have in theory entered service in tandem with the trial batch.

4 hours ago, Stuart Galbraith said:

None of this proves it achieved the general staff requirements, but it does suggest that it must have  come at least somewhere near.

Yes, nothing is proven here. It might have met the staff requirements or it might have failed to meet them. However based on simple mathematics, we know that it was not meant to penetrate an unsloped 700 mm armor grade steel "plate" or a 350 mm armor grade steel plate sloped at 60° NATO angle - because that is simply not possible based on what contemporary and current science tells us.

We know that the tank that became the CR2 (which was originally pitched together with a few other variants as upgraded CR1) did not meet all requirements of SR(L) 4026 and that even the production variant falls short of some (like the 300 mm KE roof armor capable of stopping missiles and artillery rounds with EFP warhead). That however doesn't mean that the L27A1's penetration requirement wasn't met.

4 hours ago, Stuart Galbraith said:

Is there any explanation of how it was projected to perform better than the smoothbore APFSDS rounds, or were they just downgrading them to make XL30 firing XL27 look like it was going to perform considerably better? Which is odd in itself,  because the Army seemed to actually want Abrams.

Maybe the L27A1 was designed to defeat a certain multi-layered target that the DM43 and M829A1 were not opimized against.

Maybe the performance was achieved against highly sloped steel.

Maybe this was based on the ability to overcome heavy ERA (500-600 mm steel + Kontakt-5).

Maybe the L27A1 was downgraded.

Maybe the document lists penetration values compiled from different sources that were measured/generated using different methods.

Performance is always dependent on the target. We don't really know if the L27A1 ended up being better than M829A1 and DM43 (which at the time of the document was still in very early development). The only thing that we know is that the British were expecting/projecting the L27A1 CHARM3 to exceed the performance of M829A1 and DM43 against a certain target.

M829A1 wasn't designed to defeat Kontakt-5  ERA, neither was DM43. So some optimizations in the internal design and material to better deal with heavy ERA (I think I've read somewhere on TankNet, that L27A1 uses penetrator blanks made in the US based on the newer U-Vn alloy developed for M829A2/A3) could already make a major difference.

14 hours ago, bojan said:

Yes, but no.  We had official German schematics about vulnerability of Leo 1 posted previously, apparently add-on armor did reduce 115mm APFSDS vulnerability... from 3500+m to ~2500m.

Well, in all fairness: these schematics are from 1972 and 1974. Back then, West-Germany (and other NATO members) knew very little about the current 115 mm APFSDS ammunition available to the Soviet forces. I.e. in 1974 when the protection requirements for the Leopard 2AV were made, the 115 mm APFSDS threat was simulated using the much more powerful 120 mm proto-DM13 APFSDS.

That said, based on the actual armor schematics (plate thickness and hardness), I don't think that the Leopard 1 would be able to survive any 115 mm APFSDS hit at combat ranges.

[Stuart Galbraith]

24 minutes ago, methos said:

The Challenger 2 entered service in June 1998, not in 2000. The first trial batch entered service in 1994. So the CR2 is pre-dating the L27A1. While obviously L27A1 could not enter service before the first Challenger 2, it could have in theory entered service in tandem with the trial batch.

Yes, nothing is proven here. It might have met the staff requirements or it might have failed to meet them. However based on simple mathematics, we know that it was not meant to penetrate an unsloped 700 mm armor grade steel "plate" or a 350 mm armor grade steel plate sloped at 60° NATO angle - because that is simply not possible based on what contemporary and current science tells us.

We know that the tank that became the CR2 (which was originally pitched together with a few other variants as upgraded CR1) did not meet all requirements of SR(L) 4026 and that even the production variant falls short of some (like the 300 mm KE roof armor capable of stopping missiles and artillery rounds with EFP warhead). That however doesn't mean that the L27A1's penetration requirement wasn't met.

Maybe the L27A1 was designed to defeat a certain multi-layered target that the DM43 and M829A1 were not opimized against.

Maybe the performance was achieved against highly sloped steel.

Maybe this was based on the ability to overcome heavy ERA (500-600 mm steel + Kontakt-5).

Maybe the L27A1 was downgraded.

Maybe the document lists penetration values compiled from different sources that were measured/generated using different methods.

Performance is always dependent on the target. We don't really know if the L27A1 ended up being better than M829A1 and DM43 (which at the time of the document was still in very early development). The only thing that we know is that the British were expecting/projecting the L27A1 CHARM3 to exceed the performance of M829A1 and DM43 against a certain target.

M829A1 wasn't designed to defeat Kontakt-5  ERA, neither was DM43. So some optimizations in the internal design and material to better deal with heavy ERA (I think I've read somewhere on TankNet, that L27A1 uses penetrator blanks made in the US based on the newer U-Vn alloy developed for M829A2/A3) could already make a major difference.

Well, in all fairness: these schematics are from 1972 and 1974. Back then, West-Germany (and other NATO members) knew very little about the current 115 mm APFSDS ammunition available to the Soviet forces. I.e. in 1974 when the protection requirements for the Leopard 2AV were made, the 115 mm APFSDS threat was simulated using the much more powerful 120 mm proto-DM13 APFSDS.

That said, based on the actual armor schematics (plate thickness and hardness), I don't think that the Leopard 1 would be able to survive any 115 mm APFSDS hit at combat ranges.

Ok, Im usually guilty of hair spliting on tanknet, but let me unpack that.

There certainly WERE pre production machines being evaluated by the army in 1994. I know because I think I saw one of them, V4 I think, at Bovington around that date.

Id have to check, but I really do think that the first production batch got to the army only in 1996. I do remember it was delayed 2 years after they discovered problems with the fire control, so yes, you would be right, it was 1998 before they were cleared and they started receiving the rest. And I think it must have been production end in 2001-2, when the last ones were handed over to replaced Challenger 1? Again, if I dont keep reading this stuff I struggle to remember the exact dates. The 1996 I remember, because it was Royal Scots Dragoon Guard, and I built a model of it.

All that is somewhat academic (though perhaps worth it to exercise my increasingly indurated brain). I think it very likely by that point that at least trial versions of L27 were available. I accept though, its entry into service was rather later.

The rest, yes that is very interesting indeed and I thank you for it. The point about it being optimised to penetrate Kontakt 5 is a good one, and not something Id considered.

 

Ive a British evaluation on the tank to replace chieftain, conducted in 1976, and yes, I can say that T72 was significantly underestimated in armour protection and gun power, so Im not greatly surprised.