Main Battle Tanks and Armour Technology

If Tanks have to evolve, which path they should follow?

  • Light Vehicles-Best for mobility

    Votes: 14 4.9%
  • Heavy Armour-Can take heavy punishment.

    Votes: 48 17.0%
  • Modular Design-Allowing dynamic adaptions.

    Votes: 166 58.7%
  • Universal Platform-Best for logistics.

    Votes: 55 19.4%

  • Total voters
    283

ArgonPrime

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Can u guys talk without driving into a sludge fest. Both of u are Virat nationalists so there is no room for this kind of language.

Lets start here.

1)What is a smoothbore?(Include pictures, animation if possible)
2)Explain Working Mechanism of smooth bore
3)Application and History of smooth bores.
4)Advantage of smooth bore over Rifled ones.
5) Official reports and Analysis of Smooth bore.
Well, I'd be delighted to answer your questions, but since I do not happen to be some hotshot DRDO scientist/engineer, my answers won't have any credibility whatsoever. So in light of this regrettable fact, I'll have to pass on this one with a heavy heart.

Oh and also, my broadband connection just went kaput and now I'm having have to use a fucking cellphone, that's another reason.
 

Bhumihar

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Well, I'd be delighted to answer your questions, but since I do not happen to be some hotshot DRDO scientist/engineer, my answers won't have any credibility whatsoever. So in light of this regrettable fact, I'll have to pass on this one with a heavy heart.

Oh and also, my broadband connection just went kaput and now I'm having have to use a fucking cellphone, that's another reason.
Do consider answering once u feel like it its a open platform so everyone has the right to raise questions.
 

ArgonPrime

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Do consider answering once u feel like it its a open platform so everyone has the right to raise questions.
I'm glad to hear that but it'll have to wait till my network comes online. I've been trying to contact the service provider but no luck so far.
Hey @Bleh my bro, would you please be kind enough to help this gentleman out on my stead?? Thanks in advance.
 

[email protected]

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Lets start here.

1)What is a smoothbore?(Include pictures, animation if possible)
2)Explain Working Mechanism of smooth bore
3)Application and History of smooth bores.
4)Advantage of smooth bore over Rifled ones.
5) Official reports and Analysis of Smooth bore.
No need for renewed discussion. All these related discussion have already been done on DFI on a separate thread, whose link is given as:
 

Bleh

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Hey @Bleh my bro, would you please be kind enough to help this gentleman out on my stead?? Thanks in advance.
Sorry, but my knowledge on this is very limited.

Plus the questions are very broad. 1,2,3 alone would need several thousands words. @Bhumihar should rely on Google & YouTube for those.
 

Swiftfarts

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@Bleh @Swiftfarts
@Swiftfarts , to some extent, @Bleh is right. What's really the point in going for additional T-90S which does not add any new capabilities to our present arsenal?? Now, had they gone for the MS variant, that would be understandable but this present arrangement doesn't make one bit of sense to me.
Even the MkIA is not fit for service induction!! But even then, it's got a few pluses over the T-90S such as the base armor (of course we are talking without ERA cover), post penetration survivability, crew comfort, better more accurate FCS with automatic target tracking, the addition of LWS, more advanced transmission and suspension systems, better gun depression, lower ground pressure to name a few and he just pointed out those facts. That does not make him an Arjun fanboy.

@Bleh I won't mind if the Army does decide to go for the T-14 Armata as it will utterly dominate anything our adversaries field now or will field later on. At least, it will be a better decision than what they are going to do now with 464 additional T-90S.
But this would also bring disaster for our local tank projects as it will undoubtedly kill off the NGMBT program and all the knowledge gained from and time and resources sunk in the Arjun project will go down the drain.


Post edited removed personal arguments.
T 90S provide 830- 850mm against a KE penetrator. For a 48 tonne tank from protection to fire power + logistics , it stomp's Arjun from a mile away.( I won't even go into that buying from Russia has a strategic and geopolitical angle as well ).
Rumours has it that T 90S composite armour using improved reflective plates can still stop even M829A3 APFSDS after ERA is busted from 2 km. T 90M has about 1100 - 1350mm against a KE penetrator.
55 tonne Armata on the other hand is completely a different beast all together. it stomp's Arjun and all current western tanks from protection to firepower.
India will go for Armata to replace T 72 decade down the line , probably sooner. Russia will do the same. production run will be 4000+ for both + few more countries and it will bring down costs considerably.
 
Last edited:

ArgonPrime

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Ok, now that my internet connection is stable again, finally I can try and answer your questions one by one. I warn you beforehand that It's gonna be a long-ass post, so buckle up.

Lets start here.

1)What is a smoothbore?(Include pictures, animation if possible)
As the name suggests, a smoothbore means the inner surface of the barrel is completely smooth as in there are no spiral/helical grooves swagged on the inner surface of the barrel. To explain it in simpler terms, it's basically just a metal pipe.

Here are some photographs for reference -
1.


This is the inner surface of an M 777 barrel, notice those helical grooves lined along the length of the bore?? Those are called rifling.

They are put in place in order to exert torque to a projectile, thus imparting a spin. This spin serves to gyroscopically stabilize the projectile by conservation of angular momentum, improving its aerodynamic stability and accuracy over smoothbore designs. It's basically like spinning a Beyblade.

Check this out for further reference -



2.


Now here is a photograph of Rheinmetall L/44. Here, you can see, there are no such groovings along the inner surface/bore of the barrel, hence the term 'smoothbore'.


2)Explain Working Mechanism of smooth bore
Nothing much to explain here really. It's just like how a desi one-shotter katta really. There are no groovings so there is basically nothing to stabilize the projectiles and therefore, in general, they are far inferior to their rifled counterparts, heck you can't really even compare them.

Now, you may be wondering, then why the fuck some of us have been advocating so strongly in favor of a smooth barrel gun for the Arjun, I'll come to that in a moment.

3)Application and History of smooth bores.
Well, if I'm to explain every little detail about its history and use, then I'd have to write an entire pamphlet. So we'll restrict it to tank guns only since that's what our subject of discussion is.

The first-ever smooth barrel gun for an AFV was developed by the Soviet Union in the 60s for their BMP 1s as far as I know, somebody may feel free to correct me in case I'm wrong.

Now as for tanks, I believe it's the T-62 that was the very first tank in the world to be fitted with a 115 mm U-5TS (2A20) smooth barrel gun, which significantly outperformed its NATO counterpart - the British Royal Ordnance L7. This intern led to the development of the Rheinmetall L/44 gun that eventually found its way into most of the NATO and allied MBTs.

The Soviets followed up with their 2A46 125mm L/48 smoothbores in their T-64B models and kept improving upon this design over time which was used in later Soviet/ Russian MBTs.

4)Advantage of smooth bore over Rifled ones.
If we are talking about small arms or even tube artillery pieces - there's none. But when it comes to tank guns, the smoothbore just blows its rifled counterpart out of the water, there is basically no comparison. The former edges out in every category you can rate a gun with.

Now, why is that so?? Well, remember Gyroscopic Stabilization?? It's a great thing but there's a caveat in there. It can only stabilize a projectile with a Length: Diameter ratio below 9:1, anything more than that, and it will actually begin to destabilize the projectile!!

It can be more easily explained by a real-life example, you could do the experiment yourself at your home.

You can stabilize a Beyblade by making it spin at a high enough rpm?? Now imagine trying to do the same with a more slender and longer object, a ballpoint pen for example. Can you do that?? Can you keep it stabilized in an upright position by giving it spin?? Go ahead, try it out.
So, you see the problem yet??

Modern western APFSDS penetrators have reached in the realm of over 30:1 L: D ratio and if we're to believe some of the claims being made by the Russians, their newly developed rounds for the Armata comes with a rod with an L: D ratio of hopping 40:1 (although I can not corroborate the authenticity of this claim).

Now, although Indian rounds are stubbier, a lot stubbier, in fact, they would still be in the range of 20-22:1, there's no way a rifled gun would be able to provide the necessary stabilization. Therefore the claim made by a certain individual that somehow a rifled tank gun is more accurate than a smooth barrel one - well, let's just say he's ill-informed unless somehow he's managed to develop reality-warping abilities.

The point is, a rifled gun brings nothing but disadvantages/shortcomings to the table when it comes to equipping tanks. They hold NO advantage over their smoothbore counterparts whatsoever.

Ok, let's just list the pros and cons of both designs and hopefully put this completely meaningless and redundant debate to its final resting place.

1. Rifled Guns -

I) Pros -

A)
Can fire HESH and APCBC type rounds and it would be considered an advantage if we were living in the WWII/ early cold war era. But, both types of ammunition have long since become beyond obsolete and are about as useful in a modern battlefield as is a broom handle.

II) Cons - Where to begin, cons hi cons hain yeha toh. The list is just endless but I'll give it a shot regardless. Ok, here goes nothing -

A) Greatly increased barrel wear compared to the smooth barrel guns as the groovings erode with the firing of each and every round and as a result, accuracy plummets, requiring more frequent barrel changes, which makes them more expensive to operate.

For example, a Rheinmetall L/44 has an estimated EFC barrel life of around 1500 rounds or even more whereas the British Royal Ordnance L30A1 can barely manage 500 shots if it's lucky. Now do the math.

B) Significantly more expensive, time-consuming, and involves a more complex procedure to produce as compared to the smooth barrel guns as you need specialized machinery to swag in the groovings. No such requirements for a smoothbore gun.

C) Can not be autofrettaged over a certain pressure level because then you would be risking damaging the groovings, which intern leads to reduced structural integrity and as a result, as a general rule of thumb, rifled guns can not handle higher chamber pressure, which intern limits the amount and power of the propellant you can push in the chamber, thereby further reducing muzzle energy.

D) Has noticeably lower muzzle velocity compared to smoothbore guns given every parameter (projectile mass, propellant mass, and power, barrel length to name a few) remains unchanged. What happens is that you can not properly seal the rounds inside the barrel due to the groovings and as a result, some of the energy from the propellant charges sips out through the dips in the groovings which slightly reduces available power behind the projectile.
No such issues with smoothbore guns though for obvious reasons.

E) Need for more complex APFSDS round design in order to make them compatible with the guns. As I've mentioned before, spinning a long rod at high RPMs will be greatly detrimental to its accuracy as it would either make the rods to wobble around its longitudinal axis and go haywire after exiting the barrel or just snap that thin rod into two due to the sheer stress that is imparted from spin.

Therefore, to mitigate or at least reduce the rate of spin to the bare minimum level possible, the designers need to wrap the sabot with what we call slipper bands, these are basically ring-shaped metal bands with ball bearings fitted into them which adds to the complexity and they are somewhat prone to mechanical failure as well, albeit not very commonly.

F) Continuing from the above-mentioned point, this also greatly limits your sources of ammunition procurement.

G) Can not fire HEAT rounds without complex modifications as spin fucks with the jet formation. But it's not that big of a deal anymore in my opinion as better alternatives are now available.

There are more but these are the main problem points.

Now coming to the smoothbore guns -

2. Smoothbore Guns -

I) Pros -

A)
Far higher barrel life, reduced cost, and hassle of operation.

B) Less expensive and complex to produce.

C) Can be autofrettaged at much higher pressure, thereby enabling it to use higher energetic propellant materials, which increases gun performance.

For example, the gun of Arjun is autofrettaged at ~840 MPa and the gun can withstand chamber pressure in excess of ~620 MPa whereas the much older Rheinmetall L/44 can withstand chamber pressure of over 700 MPa as they are autofrettaged at a much higher pressure level of ~1100 MPa.

D) No loss of propellant energy behind the projectile, thereby enabling the guns to propel the rounds at higher muzzle velocities.

E) Can use simpler and more effective APFSDS rounds as you do not need to compensate for the spin.

F) You'll be spoiled for choice of ammunition.

G) Can fire HEAT rounds without any problems.

II) Cons -
A)
There aren't one, really. Well, there is the fact that it can not fire HESH rounds but there are much better alternatives available these days for use against lightly armored/unarmored vehicles and field fortifications like thermobaric rounds, programmable HE, APAM or even regular HE rounds with attached fins to name a few.

The thing is, HESH is incredibly easy to defend against as in, a structure can be made HESH resistant with rather simple engineering solutions but that's for a later time.

5) Official reports and Analysis of Smooth bore.
Why?? Getting to learn the underlying laws of physics involved isn't good enough for you to be able to get to your own conclusions??
 
Last edited:

ArgonPrime

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T 90S provide 830- 850mm against a KE penetrator.
Yes, when supplemented by the Heavy ERA tiles. But I was talking about the base armor only and it's a fact that Arjun has higher LOS thickness along the frontal hemisphere (except in and around the cutaway position of the GMS obviously)
For a 48 tonne tank from protection to fire power + logistics , it stomp's Arjun from a mile away.
I won't go so far as to say stomp but yes, I see your point. The thing is though, Arjun does hold a few advantages in some of the categories as well which in some cases can be decisive.

For example, post penetration survivability of the Arjun MkIA is definitely better by an order of magnitude.

Besides, Arjun has almost twice the gun depression (8 degrees vs 5 degrees), has better mobility over most types of terrains due to higher power to weight ratio and better suspension, better FCS and sights compared to the Russian ones (Indian ones make use of homegrown FCS and french sights if I remember correcty). So it's not an absolute stomp.
( I won't even go into that buying from Russia has a strategic and geopolitical angle as well ).
No one disputes that.
Rumours has it that T 90S composite armour using improved reflective plates can still stop even M829A3 APFSDS after ERA is busted from 2 km. T 90M has about 1100 - 1350mm against a KE penetrator.
Yeahhhhhh I would take those rumors with a pinch of salt. I mean, how could they possibly determine these figures when up until recently, the Russians didn't have either a comparable tank gun or a comparable round??
Armata on the other hand is completely a different beast all together. it stomp's Arjun and all current western tanks from protection to firepower.
Arjun - yes. It stomps it to the Kingdom Come but the NATO/ USA/ Allied MBTs - well, I'm not so sure.
India will go for Armata to replace T 72 decade down the line , probably sooner. Russia will do the same. production run will be 4000+ for both + few more countries and it will bring down costs considerably.
As I said, I wouldn't really mind if that happens, it's a phenomenal piece of machinery. The only problem with this route, as I'd explained before, is that it will invariably kill off any hope for a homegrown NGMBT project, and the time and resources sunk into and the knowledge gained from the whole Arjun fiasco will go down the sewer.
 

Dessert Storm

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Ok, now that my internet connection is stable again, finally I can try and answer your questions one by one. I warn you beforehand that It's gonna be a long-ass post, so buckle up.


As the name suggests, a smoothbore means the inner surface of the barrel is completely smooth as in there are no spiral/helical grooves swagged on the inner surface of the barrel. To explain it in simpler terms, it's basically just a metal pipe.

Here are some photographs for reference -
1.


This is the inner surface of an M 777 barrel, notice those helical grooves lined along the length of the bore?? Those are called rifling.

They are put in place in order to exert torque to a projectile, thus imparting a spin. This spin serves to gyroscopically stabilize the projectile by conservation of angular momentum, improving its aerodynamic stability and accuracy over smoothbore designs. It's basically like spinning a Beyblade.

Check this out for further reference -



2.


Now here is a photograph of Rheinmetall L/44. Here, you can see, there are no such groovings along the inner surface/bore of the barrel, hence the term 'smoothbore'.



Nothing much to explain here really. It's just like how a desi one-shotter katta really. There are no groovings so there is basically nothing to stabilize the projectiles and therefore, in general, they are far inferior to their rifled counterparts, heck you can't really even compare them.

Now, you may be wondering, then why the fuck some of us have been advocating so strongly in favor of a smooth barrel gun for the Arjun, I'll come to that in a moment.


Well, if I'm to explain every little detail about its history and use, then I'd have to write an entire pamphlet. So we'll restrict it to tank guns only since that's what our subject of discussion is.

The first-ever smooth barrel gun for an AFV was developed by the Soviet Union in the 60s for their BMP 1s as far as I know, somebody may feel free to correct me in case I'm wrong.

Now as for tanks, I believe it's the T-62 that was the very first tank in the world to be fitted with a 115 mm U-5TS (2A20) smooth barrel gun, which significantly outperformed its NATO counterpart - the British Royal Ordnance L7. This intern led to the development of the Rheinmetall L/44 gun that eventually found its way into most of the NATO and allied MBTs.

The Soviets followed up with their 2A46 125mm L/48 smoothbores in their T-64B models and kept improving upon this design over time which was used in later Soviet/ Russian MBTs.


If we are talking about small arms or even tube artillery pieces - there's none. But when it comes to tank guns, the smoothbore just blows its rifled counterpart out of the water, there is basically no comparison. The former edges out in every category you can rate a gun with.

Now, why is that so?? Well, remember Gyroscopic Stabilization?? It's a great thing but there's a caveat in there. It can only stabilize a projectile with a Length: Diameter ratio below 9:1, anything more than that, and it will actually begin to destabilize the projectile!!

It can be more easily explained by a real-life example, you could do the experiment yourself at your home.

You can stabilize a Beyblade by making it spin at a high enough rpm?? Now imagine trying to do the same with a more slender and longer object, a ballpoint pen for example. Can you do that?? Can you keep it stabilized in an upright position by giving it spin?? Go ahead, try it out.
So, you see the problem yet??

Modern western APFSDS penetrators have reached in the realm of over 30:1 L: D ratio and if we're to believe some of the claims being made by the Russians, their newly developed rounds for the Armata comes with a rod with an L: D ratio of hopping 40:1 (although I can not corroborate the authenticity of this claim).

Now, although Indian rounds are stubbier, a lot stubbier, in fact, they would still be in the range of 20-22:1, there's no way a rifled gun would be able to provide the necessary stabilization. Therefore the claim made by a certain individual that somehow a rifled tank gun is more accurate than a smooth barrel one - well, let's just say he's ill-informed unless somehow he's managed to develop reality-warping abilities.

The point is, a rifled gun brings nothing but disadvantages/shortcomings to the table when it comes to equipping tanks. They hold NO advantage over their smoothbore counterparts whatsoever.

Ok, let's just list the pros and cons of both designs and hopefully put this completely meaningless and redundant debate to its final resting place.

1. Rifled Guns -

I) Pros -

A)
Can fire HESH and APCBC type rounds and it would be considered an advantage if we were living in the WWII/ early cold war era. But, both types of ammunition have long since become beyond obsolete and are about as useful in a modern battlefield as is a broom handle.

II) Cons - Where to begin, cons hi cons hain yeha toh. The list is just endless but I'll give it a shot regardless. Ok, here goes nothing -

A) Greatly increased barrel wear compared to the smooth barrel guns as the groovings erode with the firing of each and every round and as a result, accuracy plummets, requiring more frequent barrel changes, which makes them more expensive to operate.

For example, a Rheinmetall L/44 has an estimated EFC barrel life of around 1500 rounds or even more whereas the British Royal Ordnance L30A1 can barely manage 500 shots if it's lucky. Now do the math.

B) Significantly more expensive, time-consuming, and involves a more complex procedure to produce as compared to the smooth barrel guns as you need specialized machinery to swag in the groovings. No such requirements for a smoothbore gun.

C) Can not be autofrettaged over a certain pressure level because then you would be risking damaging the groovings, which intern leads to reduced structural integrity and as a result, as a general rule of thumb, rifled guns can not handle higher chamber pressure, which intern limits the amount and power of the propellant you can push in the chamber, thereby further reducing muzzle energy.

D) Has noticeably lower muzzle velocity compared to smoothbore guns given every parameter (projectile mass, propellant mass, and power, barrel length to name a few) remains unchanged. What happens is that you can not properly seal the rounds inside the barrel due to the groovings and as a result, some of the energy from the propellant charges sips out through the dips in the groovings which slightly reduces available power behind the projectile.
No such issues with smoothbore guns though for obvious reasons.

E) Need for more complex APFSDS round design in order to make them compatible with the guns. As I've mentioned before, spinning a long rod at high RPMs will be greatly detrimental to its accuracy as it would either make the rods to wobble around its longitudinal axis and go haywire after exiting the barrel or just snap that thin rod into two due to the sheer stress that is imparted from spin.

Therefore, to mitigate or at least reduce the rate of spin to the bare minimum level possible, the designers need to wrap the sabot with what we call slipper bands, these are basically ring-shaped metal bands with ball bearings fitted into them which adds to the complexity and they are somewhat prone to mechanical failure as well, albeit not very commonly.

F) Continuing from the above-mentioned point, this also greatly limits your sources of ammunition procurement.

G) Can not fire HEAT rounds without complex modifications as spin fucks with the jet formation. But it's not that big of a deal anymore in my opinion as better alternatives are now available.

There are more but these are the main problem points.

Now coming to the smoothbore guns -

2. Smoothbore Guns -

I) Pros -

A)
Far higher barrel life, reduced cost, and hassle of operation.

B) Less expensive and complex to produce.

C) Can be autofrettaged at much higher pressure, thereby enabling it to use higher energetic propellant materials, which increases gun performance.

For example, the gun of Arjun is autofrettaged at ~840 MPa and the gun can withstand chamber pressure in excess of ~620 MPa whereas the much older Rheinmetall L/44 can withstand chamber pressure of over 700 MPa as they are autofrettaged at a much higher pressure level of ~1100 MPa.

D) No loss of propellant energy behind the projectile, thereby enabling the guns to propel the rounds at higher muzzle velocities.

E) Can use simpler and more effective APFSDS rounds as you do not need to compensate for the spin.

F) You'll be spoiled for choice of ammunition.

G) Can fire HEAT rounds without any problems.

II) Cons -
A)
There aren't one, really. Well, there is the fact that it can not fire HESH rounds but there are much better alternatives available these days for use against lightly armored/unarmored vehicles and field fortifications like thermobaric rounds, programmable HE, APAM or even regular HE rounds with attached fins to name a few.

The thing is, HESH is incredibly easy to defend against as in, a structure can be made HESH resistant with rather simple engineering solutions but that's for a later time.


Why?? Getting to learn the underlying laws of physics involved isn't good enough for you to be able to get to your own conclusions??
Why don't you write an article for the front page? You write good.
 

ArgonPrime

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Why don't you write an article for the front page? You write good.
Thanks for your compliments, mate, appreciate it. But you see, the problem is, since I don't happen to be some hotshot DRDO scientist/ engineer with a post-graduate degree in applied physics from an IIT/IISc, my words have got no credibility whatsoever. So, why even bother, huh??
 

Dessert Storm

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Thanks for your compliments, mate, appreciate it. But you see, the problem is, since I don't happen to be some hotshot DRDO scientist/ engineer with a post-graduate degree in applied physics from an IIT/IISc, my words have got no credibility whatsoever. So, why even bother, huh??
You can request the mods for an "Enthusiast Article". I am sure, if they find the material compelling, might give it a shot.
Edit: Gathering information/data and presenting it in a manner that ignites thoughts, discussions, creates a POV with is an art.
 

ArgonPrime

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You can request the mods for an "Enthusiast Article". I am sure, if they find the material compelling, might give it a shot.
Well, I'm content with commenting on the regular threads for the time being. If even a single person finds my post to be helpful or at least, it raises some questions in their minds that's more than good enough for me. :)
 

ArgonPrime

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@ArgonPrime what capabilities you like to see in NGMBT ? If it did happen..... would you want it to be similar to Armata platform or something different ?
Of course, I would want it to take the Armata route. I'm pretty much sold on the whole unmanned turret, crew in the hull design philosophy. Isolated armored capsules in the hull are the best places to be inside a tank as it's a lot easier to hide the hull behind terrain covers and hence, safer against direct enemy fire.

The only thing I would do differently would be to up-armor the turret face at least. I know, I know, the Afghanit, it's a neat piece of technology but I'd want a solid back up to fall back on in case the technology fails.

Oh and I'd also try and increase gun depression angle as much as possible in view of our northern frontiers. There, in that kind of terrain, we can really put the hull-down defense to its maximum effect against onrushing PLA armored forces.

And lastly, if we are not looking for it to become operational in the near future, as in it is to become operational by 2030 or beyond, then I would also want them to do away with conventional guns altogether and adopt a Combustion light-gas gun. I mean, have you looked at the muzzle velocity this thing can achieve??!! Forget about the new Russian gun or the German 130 mm Rheinmetall prototype, Heck, forget about mass drivers/ coil guns/ rail guns, this thing just blows every competition out the water!!

For example, a 45mm technology demonstrator managed to propel a projectile at a hopping 11km/sec muzzle velocity!! It almost feels like the stuff from some sci-fi literature like HALO or Star Wars. Now try and match that with a conventional gun.

And the advantage just doesn't stop there either. Use of this technology can completely eliminate the need for the extremely hazardous propellant charges, you can make the gun smaller in diameter which in turn will enable you to pack more ammo inside your tanks, reduced barrel wear as it doesn't heat up the bore nearly as much as the present guns - the list just goes on.
 

Bleh

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Yes, when supplemented by the Heavy ERA tiles. But I was talking about the base armor only and it's a fact that Arjun has higher LOS thickness along the frontal hemisphere (except in and around the cutaway position of the GMS obviously)
IMG_20201009_231214.jpg

No, T-90 can achieve 800mm+ LOS armour from the front, two small arras at outermost part of front silhouette. But must of the central area is 300 to 450mm.

BTW, from where are you quoting Arjun gun-depression value of 8°?.. I couldn't find anything.
 

Trololo

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Ok, now that my internet connection is stable again, finally I can try and answer your questions one by one. I warn you beforehand that It's gonna be a long-ass post, so buckle up.


As the name suggests, a smoothbore means the inner surface of the barrel is completely smooth as in there are no spiral/helical grooves swagged on the inner surface of the barrel. To explain it in simpler terms, it's basically just a metal pipe.

Here are some photographs for reference -
1.


This is the inner surface of an M 777 barrel, notice those helical grooves lined along the length of the bore?? Those are called rifling.

They are put in place in order to exert torque to a projectile, thus imparting a spin. This spin serves to gyroscopically stabilize the projectile by conservation of angular momentum, improving its aerodynamic stability and accuracy over smoothbore designs. It's basically like spinning a Beyblade.

Check this out for further reference -



2.


Now here is a photograph of Rheinmetall L/44. Here, you can see, there are no such groovings along the inner surface/bore of the barrel, hence the term 'smoothbore'.



Nothing much to explain here really. It's just like how a desi one-shotter katta really. There are no groovings so there is basically nothing to stabilize the projectiles and therefore, in general, they are far inferior to their rifled counterparts, heck you can't really even compare them.

Now, you may be wondering, then why the fuck some of us have been advocating so strongly in favor of a smooth barrel gun for the Arjun, I'll come to that in a moment.


Well, if I'm to explain every little detail about its history and use, then I'd have to write an entire pamphlet. So we'll restrict it to tank guns only since that's what our subject of discussion is.

The first-ever smooth barrel gun for an AFV was developed by the Soviet Union in the 60s for their BMP 1s as far as I know, somebody may feel free to correct me in case I'm wrong.

Now as for tanks, I believe it's the T-62 that was the very first tank in the world to be fitted with a 115 mm U-5TS (2A20) smooth barrel gun, which significantly outperformed its NATO counterpart - the British Royal Ordnance L7. This intern led to the development of the Rheinmetall L/44 gun that eventually found its way into most of the NATO and allied MBTs.

The Soviets followed up with their 2A46 125mm L/48 smoothbores in their T-64B models and kept improving upon this design over time which was used in later Soviet/ Russian MBTs.


If we are talking about small arms or even tube artillery pieces - there's none. But when it comes to tank guns, the smoothbore just blows its rifled counterpart out of the water, there is basically no comparison. The former edges out in every category you can rate a gun with.

Now, why is that so?? Well, remember Gyroscopic Stabilization?? It's a great thing but there's a caveat in there. It can only stabilize a projectile with a Length: Diameter ratio below 9:1, anything more than that, and it will actually begin to destabilize the projectile!!

It can be more easily explained by a real-life example, you could do the experiment yourself at your home.

You can stabilize a Beyblade by making it spin at a high enough rpm?? Now imagine trying to do the same with a more slender and longer object, a ballpoint pen for example. Can you do that?? Can you keep it stabilized in an upright position by giving it spin?? Go ahead, try it out.
So, you see the problem yet??

Modern western APFSDS penetrators have reached in the realm of over 30:1 L: D ratio and if we're to believe some of the claims being made by the Russians, their newly developed rounds for the Armata comes with a rod with an L: D ratio of hopping 40:1 (although I can not corroborate the authenticity of this claim).

Now, although Indian rounds are stubbier, a lot stubbier, in fact, they would still be in the range of 20-22:1, there's no way a rifled gun would be able to provide the necessary stabilization. Therefore the claim made by a certain individual that somehow a rifled tank gun is more accurate than a smooth barrel one - well, let's just say he's ill-informed unless somehow he's managed to develop reality-warping abilities.

The point is, a rifled gun brings nothing but disadvantages/shortcomings to the table when it comes to equipping tanks. They hold NO advantage over their smoothbore counterparts whatsoever.

Ok, let's just list the pros and cons of both designs and hopefully put this completely meaningless and redundant debate to its final resting place.

1. Rifled Guns -

I) Pros -

A)
Can fire HESH and APCBC type rounds and it would be considered an advantage if we were living in the WWII/ early cold war era. But, both types of ammunition have long since become beyond obsolete and are about as useful in a modern battlefield as is a broom handle.

II) Cons - Where to begin, cons hi cons hain yeha toh. The list is just endless but I'll give it a shot regardless. Ok, here goes nothing -

A) Greatly increased barrel wear compared to the smooth barrel guns as the groovings erode with the firing of each and every round and as a result, accuracy plummets, requiring more frequent barrel changes, which makes them more expensive to operate.

For example, a Rheinmetall L/44 has an estimated EFC barrel life of around 1500 rounds or even more whereas the British Royal Ordnance L30A1 can barely manage 500 shots if it's lucky. Now do the math.

B) Significantly more expensive, time-consuming, and involves a more complex procedure to produce as compared to the smooth barrel guns as you need specialized machinery to swag in the groovings. No such requirements for a smoothbore gun.

C) Can not be autofrettaged over a certain pressure level because then you would be risking damaging the groovings, which intern leads to reduced structural integrity and as a result, as a general rule of thumb, rifled guns can not handle higher chamber pressure, which intern limits the amount and power of the propellant you can push in the chamber, thereby further reducing muzzle energy.

D) Has noticeably lower muzzle velocity compared to smoothbore guns given every parameter (projectile mass, propellant mass, and power, barrel length to name a few) remains unchanged. What happens is that you can not properly seal the rounds inside the barrel due to the groovings and as a result, some of the energy from the propellant charges sips out through the dips in the groovings which slightly reduces available power behind the projectile.
No such issues with smoothbore guns though for obvious reasons.

E) Need for more complex APFSDS round design in order to make them compatible with the guns. As I've mentioned before, spinning a long rod at high RPMs will be greatly detrimental to its accuracy as it would either make the rods to wobble around its longitudinal axis and go haywire after exiting the barrel or just snap that thin rod into two due to the sheer stress that is imparted from spin.

Therefore, to mitigate or at least reduce the rate of spin to the bare minimum level possible, the designers need to wrap the sabot with what we call slipper bands, these are basically ring-shaped metal bands with ball bearings fitted into them which adds to the complexity and they are somewhat prone to mechanical failure as well, albeit not very commonly.

F) Continuing from the above-mentioned point, this also greatly limits your sources of ammunition procurement.

G) Can not fire HEAT rounds without complex modifications as spin fucks with the jet formation. But it's not that big of a deal anymore in my opinion as better alternatives are now available.

There are more but these are the main problem points.

Now coming to the smoothbore guns -

2. Smoothbore Guns -

I) Pros -

A)
Far higher barrel life, reduced cost, and hassle of operation.

B) Less expensive and complex to produce.

C) Can be autofrettaged at much higher pressure, thereby enabling it to use higher energetic propellant materials, which increases gun performance.

For example, the gun of Arjun is autofrettaged at ~840 MPa and the gun can withstand chamber pressure in excess of ~620 MPa whereas the much older Rheinmetall L/44 can withstand chamber pressure of over 700 MPa as they are autofrettaged at a much higher pressure level of ~1100 MPa.

D) No loss of propellant energy behind the projectile, thereby enabling the guns to propel the rounds at higher muzzle velocities.

E) Can use simpler and more effective APFSDS rounds as you do not need to compensate for the spin.

F) You'll be spoiled for choice of ammunition.

G) Can fire HEAT rounds without any problems.

II) Cons -
A)
There aren't one, really. Well, there is the fact that it can not fire HESH rounds but there are much better alternatives available these days for use against lightly armored/unarmored vehicles and field fortifications like thermobaric rounds, programmable HE, APAM or even regular HE rounds with attached fins to name a few.

The thing is, HESH is incredibly easy to defend against as in, a structure can be made HESH resistant with rather simple engineering solutions but that's for a later time.


Why?? Getting to learn the underlying laws of physics involved isn't good enough for you to be able to get to your own conclusions??
this is a very good explanation. thank you! but why then is the Challenger 2's rifled gun so hyped about its legendary accuracy and killing capability?
 

ArgonPrime

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No, T-90 can achieve 800mm+ LOS armour from the front, two small arras at outermost part of front silhouette. But must of the central area is 300 to 450mm.
You're confusing LOS thickness with effective thickness. It may very well have ~800 mm LOS thickness at certain parts from certain angles but that doesn't mean this will provide effective protection value of 850+ mm.
BTW, from where are you quoting Arjun gun-depression value of 8°?.. I couldn't find anything.
The guys over at the tanknet had estimated it to be so.
 
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ArgonPrime

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this is a very good explanation. thank you! but why then is the Challenger 2's rifled gun so hyped about its legendary accuracy and killing capability?
Because that's how propaganda works. The Challenger 2 got shafted by every other NATO MBTs in multiple tank competitions throughout the late 80s and early 90s.

During a demonstration in front of Egyptian Army delegates (Egypt was at that time in the market looking to buy a brand new MBT), a Challenger MkII missed the first 28 out of 28 consecutive shots and of course, the deal fell through.

But when one lucky Challenger manages to nail a T-55 from 4.7 km and lo and behold - Challenger's got the most accurate gun in the world and rifled guns are suddenly more accurate than smoothbore ones. The problem lies in us, we never stop to think about anything for even a second and just jump on the hype train.
 

Trololo

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Because that's how propaganda works. The Challenger 2 got shafted by every other NATO MBTs in multiple tank competitions throughout the late 80s and early 90s.

During a demonstration in front of Egyptian Army delegates (Egypt was at that time in the market looking to buy a brand new MBT), a Challenger MkII missed the first 28 out of 28 consecutive shots and of course, the deal fell through.

But when one lucky Challenger manages to nail a T-55 from 4.7 km and lo and behold - Challenger's got the most accurate gun in the world and rifled guns are suddenly more accurate than smoothbore ones. The problem lies in us, we never stop to think about anything for even a second and just jump on the hype train.
So can we say its the Vijayanta experience and British tank influence for the rifled gun on the Arjun? Else we could have taken the gun of the Leopard 2.
 

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