Benefits of larger caliber main guns against tanks

[Samsa]

With the new KNDS and Rheinmetall demonstrators predictably allowing for 130/140mm guns - in my understanding mostly for added armor penetration - I've heard some more doubts about the general usefulness of the larger calibers.

Especally with the rather large amount of documented tank losses recently, I myself also wonder wether that is the right move.

Many of the tanks getting hit and not penetrated seem to be abandoned or at least need to retreat anyways. That suggests, that the tactical objective of "get the enemy out of that area" can be achieved quite often via mission kill without full penetration. 

Plus, even if it weren't so, it seems that engagements vs a heavily armed targets in the frontal arc are a rather small percentage of all tank engagements in this war, making smaller guns good enough for most cases.

Also the most recent designs seem to reduce turret armor and move the crew below the turret ring anyways, making missions kills vs the turret easier for smaller guns. Crewless turrets also obviously rely on sensors for Situational awareness too which, I suppose, are also susceptible to fragment damage from non penetrating hits or HE hits.

I can see the better HE effect of larger rounds as a benefit, but that doesn't seem the driving factor behind these developments to me. Does having the ability to penetrate the crew capsule of an Armata from the front really warrant the costs of increasing caliber?

I know this topic comes up mixed in in different threads every now and then. Still, I'd be interested in hearing some opinions on this in a dedicated discussion

[Mighty_Zuk]

On 6/21/2024 at 2:46 PM, Samsa said:

Especally with the rather large amount of documented tank losses recently, I myself also wonder wether that is the right move.

Many of the tanks getting hit and not penetrated seem to be abandoned or at least need to retreat anyways. That suggests, that the tactical objective of "get the enemy out of that area" can be achieved quite often via mission kill without full penetration. 

There are 2 important aspects to this:

1. Ukraine and Russia have unique circumstances in that their tank fleets are massively behind the curve in terms of technology, including western tanks donated to Ukraine (they were high end... 30 years ago), while both employ some forms of innovative and new forms of munitions and technology, creating atypical and unhealthy asymmetry. Hence the tanks are unable to really cope with even these seemingly simple threats.

2. Behind the scenes, tanks and other AFVs are destroyed after every battle - to prevent their recovery or capture.

On 6/21/2024 at 2:46 PM, Samsa said:

Plus, even if it weren't so, it seems that engagements vs a heavily armed targets in the frontal arc are a rather small percentage of all tank engagements in this war, making smaller guns good enough for most cases.

This has always been the case. A good crew, in a well trained formation, backed by modern technology and a robust organization, know to point the strongest armor at the enemy and prevent exposure of weak points, and operate under layers of protection. And a well designed tank is supposed to be able to single handedly defeat every conceivable threat within direct fire range, including the most armored targets, because its task is to provide the ultimate firepower to a given area.

On 6/21/2024 at 2:46 PM, Samsa said:

Also the most recent designs seem to reduce turret armor and move the crew below the turret ring anyways, making missions kills vs the turret easier for smaller guns. Crewless turrets also obviously rely on sensors for Situational awareness too which, I suppose, are also susceptible to fragment damage from non penetrating hits or HE hits.

Unmanned turrets are actually not any more vulnerable than manned turrets, even if they lack meaningful armor, and neither are they noticeably more vulnerable to sensory damage. 

Manned platforms with manned turrets are packed to the brim with various sensitive and critical systems and sensors. Hitting them would hurt a lot, regardless of whether there's someone in the turret or not. The key is to be able to produce, deliver, and replace such parts quickly.

As for armor, on manned turrets there isn't really armor all around. It protects the crew against projectiles coming from predicted angles. But it doesn't protect the turret's systems all that much. The gun is even more exposed than it was before composite armor, and ammo is often not really behind armor, or at least a lot of armor. Just separate from the crew. Not to mention all the critical systems on the turret roof or in the bustle area.

On 6/21/2024 at 2:46 PM, Samsa said:

I can see the better HE effect of larger rounds as a benefit, but that doesn't seem the driving factor behind these developments to me. Does having the ability to penetrate the crew capsule of an Armata from the front really warrant the costs of increasing caliber?

That's a dilemma. Hence the various schools of thought pitching ideas anywhere from simply stronger 120mm up to conventional 140mm. In between are lower power 140mm (French), conventional 130mm (German), and mixes with other armaments. But the common denominator for them is that for the forseeable future, they should be able to penetrate any armored target they come across, as per the defining aspects of an MBT. The cost is obvious - bigger gun = fewer rounds. 

This tradeoff is much more fathomable today than it was, say, 20 years ago, because today there are many more things that shoot, and therefore the burden on a tank to provide firepower, is much lower. Guided artillery and mortars, handheld loitering munitions, ATGMs of various sizes, on-call UAVs, etc. Today there are a LOT of tools to provide firepower that matches the target type. So an MBT is more of a niche vehicle. But when it's called to fill that niche, it should do it as best it can. 

[Nick the Noodle]

Overmatching.  Generally speaking, if the diameter of a round is double that of the enemy armour, the slope/angle of the enemy armour doesn't count towards protection.  Given that a tanks armour actual thickness is about 120mm, although heavily sloped, its effective thickness drops back to 120mm if a incoming round is 240mm. 

 

[bojan]

Jesus Christ on the pogo stick

1. That is not how armor works

2. Diameter of 120mm APFSDS round is 20somethng (let's say 30) mm.

3. Every "thick" armor on modern tanks is made with much thinner layers inside.

Edited June 25 by bojan

[sunday]

Now you will say that neither World of Tanks nor War Thunder are armor modelling software.

Edited June 25 by sunday

[Ssnake]

Maybe we'll reintroduce full caliber APHE.

🤪

[seahawk]

7 hours ago, Ssnake said:

Maybe we'll reintroduce full caliber APHE.

🤪

Against AFVs and pillboxes.

[Interlinked]

some sort of penetration-cum-blast shell mayhaps

[Stuart Galbraith]

183mm HESH, its the only way to be sure.

https://www.youtube.com/watch?v=O798fE34VyA

[KV7]

I think there is an advantage to going to a larger calibre but without a huge power increase, in this way you get better results against other targets without much cost. Also at some point HE starts to be effective vs many armoured targets and so you can take a more HE heavy load.

Actually at some point you can ditch HEAT altogether as anything that would be ordinarily engaged with it and not APFSDS can be reliable wrecked with a sufficiently powerful HE.

Another upside is that you get a better indirect fire capability.

[Stuart Galbraith]

The Russians have been flirting with the idea of having a 152mm armed Armata, which can wreck western tanks with pure HE. It would work, whether that is a really cost effective means of killing tanks considering how few rounds you can carry, is where I start having misgivings. I suspect 130-140 is about the largest feasable size, before you either have to scale the tank up over 100 tons to get a bigger gun and it all starts getting a bit silly, or you have to go back to the bagged charge or even liquid propellent system to squeeze it into MBT size. Its going to be very costly to integrate that with an autoloader system, which Is where I suspect we are headed next.

You have to wonder if it wouldnt just be a lot easier to go for indirect attacks conducted a lot further back using some kind of guided weapon.

 

[EchoFiveMike]

155mm HE M795 for everything.  If you want to be fancy, smoothbore and use a screw on fin assembly compatible with a screw on base bleed setup.  S/F...Ken M

[Pavel Novak]

Wouldn't there be problem with accuracy with slow large HE rounds trying to hit tank at 2500 m?

[Samsa]

On 6/23/2024 at 11:13 AM, Mighty_Zuk said:

...

Thanks for the thorough reply!

 

On 6/23/2024 at 11:13 AM, Mighty_Zuk said:

2. Behind the scenes, tanks and other AFVs are destroyed after every battle - to prevent their recovery or capture.

Agreed, but does not support the idea of focussing on disabling a vehicle instead of destroying it? Especially in a situation where using drones to demolish disabled vehicles seems to become the norm.

 

On 6/23/2024 at 11:13 AM, Mighty_Zuk said:

This has always been the case. A good crew, in a well trained formation, backed by modern technology and a robust organization, know to point the strongest armor at the enemy and prevent exposure of weak points, and operate under layers of protection. And a well designed tank is supposed to be able to single handedly defeat every conceivable threat within direct fire range, including the most armored targets, because its task is to provide the ultimate firepower to a given area.

 While I do have the feeling things are moving towards the necessity of better all-round-protection and the fontal arc is indeed mostly applicable to protection from guns I don't want to widen this to discuss towards the protection aspect. Regarding firepower however, would it not make sense to fill the niche of actually destroying a tank via ATGMs  - which they can do anyways - and not burden that task on the main gun. Especially if 120/125mm guns seem to be quite capable of disabling a modern vehicle from any aspect - even if they might not destroy it beyond recovery.

I have to admit though, I don't have any concrete data on how often tanks got abandoned after taking a main gun hit and how often the armor actually shrugged off the round and the tank could fight on. I am mostly talking based on the impression I got from what we can see in Ukraine OSINT wise. Yet, that impression still is, even more so than it already was in WW2, if a main gun hit lands on the enemy tank before they land one on you, the engagement is won regardless of gun caliber (within reasonable calibers of course).

[Mighty_Zuk]

1 hour ago, Samsa said:

Agreed, but does not support the idea of focussing on disabling a vehicle instead of destroying it? Especially in a situation where using drones to demolish disabled vehicles seems to become the norm.

1. Those vehicles are disabled easily because they weren't brought to a modern standard and are effectively older than probably most members of this forum, while the munitions are modern. A modern vehicle would not be disabled so easily. 

2. Russia and Ukraine do not really bother, for a range of reasons, to recover disabled vehicles. So for them disabled = destroyed. But that's not the case everywhere, and a more capable army would recover the vehicle and repair it (in the majority of cases).

1 hour ago, Samsa said:

Regarding firepower however, would it not make sense to fill the niche of actually destroying a tank via ATGMs  - which they can do anyways - and not burden that task on the main gun. Especially if 120/125mm guns seem to be quite capable of disabling a modern vehicle from any aspect - even if they might not destroy it beyond recovery.

This concept was attempted back when ATGMs were already quite accurate and there weren't any pesky APS swatting them down. The idea was abandoned primarily because an ATGM is slow and thus exposes the vehicle for a long time. Today one half - the exposure issue - is solved, with F&F missiles, but the other half - it being slow - wasn't solved. In fact there's a case to be made that faster ATGMs will overall provide less value as ATGMs effectively double as valuable ISR assets.

But if the missile is F&F, why does it matter if it's slow? Because you want to make sure the target you shot at was hit, and was hit in a meaningful way. You want to know it can't shoot back. And if you're busy looking at the video feed, you're not really engaging other targets.

Second, there are now additional problems like short range engagements, which are by no means a minority. In fact it's very common for tanks to engage targets at short distances, where ATGMs typically don't even arm yet. You could say it was an issue back then as well, but today as vehicles are increasingly sophisticated, there's much less incentive to create more variants. 

Additional issues are cost - missiles cost more than dumb shells, sorry. There's time to target - yes I talked about slow missiles but for a different reason. It adds the issue that you may want to send a shot immediately because the target is time sensitive. So you may not have those 30-ish seconds to begin with.

Of course there's also the issue of training. If you want long range missiles on it, then it's essentially artillery and the crew are trained to perform more like artillery. If the missiles are shorter range, then they're really quite limited in the types of targets they can hit in the first place. So will you now add into every platoon or company a vehicle that's not really usable a good chunk of the time?

And finally there's APS. It's true that there are some APS developments intended to defeat APFSDS, including some laboratory environment demonstrations. But the challenges are immense, and for now a large caliber gun is much more capable at penetrating a tank's defenses and then its armor, than an ATGM is.

 

[alejandro_]

4 hours ago, Pavel Novak said:

Wouldn't there be problem with accuracy with slow large HE rounds trying to hit tank at 2500 m?

I have not come across this issue. A T-80U received a 152mm (rifled) gun back in the late 80s. Results are still classified but they were judged as satisfactory. In this configuration ammunition load was 30 rounds; Armata should carry more as chassis is longer (it has an extra roadwheel), this configuration was apparently chosen in case customer wanted to move to a bigger caliber. 

https://alejandro-8.blogspot.com/2015/03/t-80-con-canon-de-152mm-objeto-292.html

[DB]

I don't see anything in latest iteration of tanks that significantly reduces their vulnerability to M-Kill with a drone-like coup-de-grace if they've been abandoned.

Sure, APS will reduce the likelihood of an individual hit by main gun rounds, ATGMs and perhaps artillery, but a significant number of the videos we see where a vehicle has been disabled and then killed at leisure have been mined, or struck repeatedly by drones that have been obviously aimed at rear decks with the target being the engine. If you start to gate drone velocities into APS systems, you're going to murder a lot of crows.

 

[Mike1158]

I have yet to see, and correct me if I am wrong, ANY meaningful defence system a la Trophy in action.

 

I thought these systems were suppsed to make AFV safe from ATGM's so drones and some main gun shells should be easy prey.  Why is this?

 

Or am I buttering my toast on both sides again?

[Stuart Galbraith]

Drones travel significantly slower. If you target the system towards slow moving targets, then its going to be the glorious twelfth of August, as far as local bird populations are concerned. Unless of course you just turn the system on when you get raid warning, which is a possible option.

I dont think the answer is going to be on the vehicle at all. I think there needs to be a thought in terms of battlegroup defence, which probably means bringing along a vehicle that carries a lot of drones itself, a vehicle carrying terminal defence systems, ie SPAA, or most likely both.

[Burncycle360]

Advanced 120mm remains entirely adequate for western tanks, IMO given that legacy and contemporary threat MBT remain significantly lighter as a design choice.  

 

The Russians and Chinese do have reason to up gun, however. Western MBT are already nearing the limit of practical weights in order to resist 125mm, so upgunning represents a relatively low cost way to render western MBT vulnerable that can still make use of their existing platforms.  

It's a relatively inexpensive way to disrupt the current paradigm, and such a move would be disproportionately effective in putting evolutionary pressure on future western MBT design considerations.

if 70 ton vehicles are adequate to defeat 125mm class weapons but inadequate to defeat 130-140mm class weapons, the result would be a schism in design philosophy into three camps:

 

Camp 1 would suggest that there's no reason to have tanks that heavy anymore if they aren't effective against the primary threat weapon system and will push for a return to lighter 50 ton tanks for mobility considerations, and rely on future APS improvements to defeat APFSDS class threats

 

Camp 2 will suggest keeping the weight and design philosophy in case you encounter legacy 125mm, and rely on future APS improvements to defeat APFSDS class threats 

 

Camp 3 will suggest keeping the weight (or slight weight reduction) but eschew passive defeat of legacy 125mm frontally and instead advocate to redistribute the armor with an emphasis on better all around CE protection, and rely on future APS improvements to defeat APFSDS class threats

 

All 3 camps will be further subdivided into those who prefer novel design approaches (unmanned turrets) and those who don't feel the fightability tradeoffs are worth it and prefer conventional layouts.  The former will gain the most traction if HIC is on the horizon while the latter will have more sway if it looks like we might get embroiled in COIN/LIC/MIC.

 

A small 4th camp that believes future APS will not be able to reliably defeat APFSDS class threats will suggest using novel design approaches / unmanned turrets while also going heavier to class 90 vehicles to defeat the new threats conventionally, but it won't be seriously considered due to weight limitations of supporting assets; you'd not only be replacing the MBT but also all the other supporting assets (LCAC, bridging, prime movers, etc) and will be rejected on cost grounds. 

 

(Another minority camp will propose the MBT is obsolete now and bombard you with powerpoint presentations and buzzwords regarding network centric warfare and UGVs, and these heathens are to be slapped with fish until they repent)

So basically a relatively inexpensive armament change by the OPFOR can be disruptive and cost a lot of time, money and infighting. 

Edited June 27 by Burncycle360

[TrustMe]

If you look at Russia in Ukraine, they don't seem to want or need an upgraded of the 125mm gun. They perceive the current one good enough even though Ukraine uses Western tanks like Abrams and Challenger 2's.

[Mighty_Zuk]

21 hours ago, Mike1158 said:

I have yet to see, and correct me if I am wrong, ANY meaningful defence system a la Trophy in action.

 

I thought these systems were suppsed to make AFV safe from ATGM's so drones and some main gun shells should be easy prey.  Why is this?

 

Or am I buttering my toast on both sides again?

Despite modern APS being operational for about 15 years, its acquisition outside Israel was slow. And even then, Trophy was massively popular. Iron Fist had some success, but it's not really operational yet. 

So you don't see the success of systems a la Trophy, because there are no systems a la Trophy in service.

[Burncycle360]

3 hours ago, TrustMe said:

If you look at Russia in Ukraine, they don't seem to want or need an upgraded of the 125mm gun. They perceive the current one good enough even though Ukraine uses Western tanks like Abrams and Challenger 2's.

 

Russia is still woefully broke and using old war stock, and for the vast majority of the conflict if they were going to encounter AFVs it would be former soviet AFVs for which 125mm is adequate. They are not agile enough in their present state to reliably respond against weaponized commercial drones, much less consider relatively major mid-war alterations like upgrading standard armament.  

This isn't WW2 or even the cold war, they are functionally incapable of multiple major iterative development cycles within the span of this conflict, and it's not because the tech is too advanced, it's because the underlying foundation has eroded that badly. They're scrambling to get more of what their limited industrial infrastructure is already set up to output;  there aren't thousands of Armata and Felons quietly being produced to unleash in some surge later on, they're begging and borrowing from China and Nork just to keep the guns warm.

This is very much a "come as you are" / "fight with what you brought" war for Russia, they didn't think it would drag on this long.  

[KV7]

On 6/26/2024 at 7:06 PM, Pavel Novak said:

Wouldn't there be problem with accuracy with slow large HE rounds trying to hit tank at 2500 m?

Who says they must be slow ? I was only saying that there is no case for a massively overpowered gun used as a specialised APFSDS thrower if there also is a calibre increase. 

I think you would want to get full calibre HE to 700 m/s + and that should be fine for typical ranges vs generic targets, and then use barrel launched ATGM or guided artillery munitions at very long range where precision is needed (against infantry at 3000 metres unguided HE will work just fine). Below 3000 to 3500 metres vs armoured vehicles you can use APFDS. 

Larger ATGM also have the advantage that the electronics have the same cost, take up less of the internal volume by proportion, and also if they are large enough they can have some secondary use vs structures, i.e. using some dual use or programmable HEAT/FRAG type munition without being inadequate as anti tank weapons. 

[KV7]

On 6/28/2024 at 8:31 AM, Burncycle360 said:

 

Russia is still woefully broke and using old war stock, and for the vast majority of the conflict if they were going to encounter AFVs it would be former soviet AFVs for which 125mm is adequate. They are not agile enough in their present state to reliably respond against weaponized commercial drones, much less consider relatively major mid-war alterations like upgrading standard armament.  

This isn't WW2 or even the cold war, they are functionally incapable of multiple major iterative development cycles within the span of this conflict, and it's not because the tech is too advanced, it's because the underlying foundation has eroded that badly. They're scrambling to get more of what their limited industrial infrastructure is already set up to output;  there aren't thousands of Armata and Felons quietly being produced to unleash in some surge later on, they're begging and borrowing from China and Nork just to keep the guns warm.

This is very much a "come as you are" / "fight with what you brought" war for Russia, they didn't think it would drag on this long.  

Even going forward the bulk of the tank fleet will use 125mm and this is sensible, in most plausible conflicts having a sufficiently large fleet of refurbished and upgraded 125mm armed tanks is going to be the more critical factor, and so if there is a new larger gun fielded it will likely be a niche thing in a high-low mix. Perhaps at large enough numbers it might be enough to cause the problems you describe above. 

The only caveat here is that maybe a deep modernisaton of T-series tanks using a new turret might make sense, but I am inclined against this.