Role of Light Tanks

[Feanor]

I was wondering about the role of light tanks today, as well as where exactly the line lies between a mobile gun system, and a light tank.

What got me thinking about this is the Sprut-SD used by the Russian VDV. It started life as the Sprut anti-tank gun project, and its first iteration was the Sprut-B, a replacement for the MT-12 Rapira towed AT gun used in anti-tank arty btlns. The Sprut-SD is the self-propelled air-droppable variant. However it's essentially a light tank, small armored chassis, turreted weapon system etc. Things are more complicated because the force org is that of an artillery btln (in Russian terminology arty is all high-caliber gun systems, not just the indirect fire ones). In other words 3 guns/tanks is a platoon, 6 is a battery/company, 18 is a btln. Also Russian military and press continue to refer to it as an SP anti-tank gun. Now this would be a mostly academic discussion, because the Sprut-SD is out of production, and only 45 have been purchased.

However the VDV has recently ordered a new light tank. This time they're calling it a light tank, and it's supposedly a 2A46 main gun, on a BMD-4M chassis and a new turret. It's unclear what force org it will use (tank btlns have two force orgs, 31 tanks, in 3 ten-tank companies, and 41, with 4 companies). It's also unclear at what level they will be inserted into the VDV structure (1 btln/regiment, per division, per brigade, and whether it will be all VDV units, para-assault ones, or paradrop ones). It's also unclear how they will relate to the current Sprut-SD, since the systems are less then a year old, and probably won't be getting phased out. They could just keep calling the Sprut-SD an anti-tank system, and the new vehicle a tank, and have them serve side by side, but it wouldn't change the fact that they'd be filling the same role.

It gets more interesting when you realize that self-propelled 125mm guns are planned on the Kurganets (IFV) and Bumerang (APC) chassis. The Bumerang-based variant has been repeatedly called a wheeled tank, and they may replace MBTs in the current Motor-Rifle Brigade force org. So this leads me to ask, what roles to light tanks fill current, and where exactly the line between a mobile gun system and a light tank lies.

 

[SpudmanWP]

If you are taking a “light” tank against another tank… you’re doing it wrong. Any “light tank” worth its salt will have at least a 90mm gun which should open up anything less than a T-72.

That being said, I think the ideal setup would be a breach loading 120mm mortar for a main gun.

1. Stop calling it a tank. Call it what it is, an Infantry Support Gun.
2. Ammo compatibility with the rest of your forces
3. OTS Ammo diversity
4. PGMs allow for pinpoint fire support yet still allow for a direct fire (think bunker buster) role.
5. A mortar is a low pressure gun so the chassis can be lighter or dedicate more of the allocated weight to armor.
6. 120mm bore-launched AT missile available as needed (ala LAHAT).

Before you think that I’m anti tanks…. I was an M1 crewman in the late ‘80s.

 

[Feanor]

If you are taking a “light” tank against another tank… you’re doing it wrong. Any “light tank” worth its salt will have at least a 90mm gun which should open up anything less than a T-72.

That being said, I think the ideal setup would be a breach loading 120mm mortar for a main gun.

1. Stop calling it a tank. Call it what it is, an Infantry Support Gun.
2. Ammo compatibility with the rest of your forces
3. OTS Ammo diversity
4. PGMs allow for pinpoint fire support yet still allow for a direct fire (think bunker buster) role.
5. A mortar is a low pressure gun so the chassis can be lighter or dedicate more of the allocated weight to armor.
6. 120mm bore-launched AT missile available as needed (ala LAHAT).

Before you think that I’m anti tanks…. I was an M1 crewman in the late ‘80s.

So like a Nona-S but with additional capabilities, and more PGMs? What level of protection/chassis would be ideal?

[ame="http://en.wikipedia.org/wiki/2S9_Nona"]2S9 Nona - Wikipedia, the free encyclopedia[/ame]

 

[Abraham Gubler]

That being said, I think the ideal setup would be a breach loading 120mm mortar for a main gun.

1. Stop calling it a tank. Call it what it is, an Infantry Support Gun.
2. Ammo compatibility with the rest of your forces
3. OTS Ammo diversity
4. PGMs allow for pinpoint fire support yet still allow for a direct fire (think bunker buster) role.
5. A mortar is a low pressure gun so the chassis can be lighter or dedicate more of the allocated weight to armor.
6. 120mm bore-launched AT missile available as needed (ala LAHAT).

I’m highly sceptical of this perennial proposal because a 120mm mortar is not an adequate direct fire weapon. While an excellent mortar and PGM firer a horizontal flight path 120mm mortar bomb is not going to knock out any kind of half decent bunker. Or any kind of structure made from reinforced brick or concrete. The mortar bomb wall is just too weak and doesn’t have enough kinetic energy to do anything more than peck at the surface of most direct fire targets.

The best infantry support gun is a tank. It has the armour to take hits and in the case of the 120mm smoothbore gun it now has all the right types of ammunition for infantry support. If you needed a lightweight infantry support gun then a turretless AFV with thick frontal hull armour and a high velocity gun could do the job. You could easily build something like this with an L7 gun with 40 rounds and RPG/23mm AP proof armour (all angle) for around 20-25 tonnes.

 

[SpudmanWP]

I think the NEMO on a medium tracked hull (CV90, etc) would work. There has been a lot of work on direct fire mortars and the 3 meter length of the barrel means that the round travels much faster and flatter than a traditional mortar. A mounted gun also means that the rounds can pack more charges than normal due to a beefier bore.

That should take care of 95% of the walls & targets in the battlefield. Add the indirect fire capability of a mortar and you start to see my point.

 

[Abraham Gubler]

I think the NEMO on a medium tracked hull (CV90, etc) would work. There has been a lot of work on direct fire mortars and the 3 meter length of the barrel means that the round travels much faster and flatter than a traditional mortar. A mounted gun also means that the rounds can pack more charges than normal due to a beefier bore.

Mortar velocity is limited by the aerodynamics of the mortar bomb. If it goes too fast it becomes unstable. NEMO, XM325, etc all still have very low muzzle velocity for direct fire weapons. Even if you change the shape of the bomb, like the Brandt heavy 120mm (rifled mortar), then you are still limited in velocity by charge. If you increase the firing velocity then it’s pretty much no longer a mortar and starts to become a gun… with all the required recoiling system, larger magazine size and so on requiring additional weight and volume to install on your vehicle.

That should take care of 95% of the walls & targets in the battlefield.

Not as simple as that. Even if you could defeat 95% of battlefield targets if those remaining 5% are the enemy’s bunkers your weapon is pretty useless in infantry support. Because those notional 5% of targets are the very reason you want an infantry support tank in the battle.

A 120mm mortar bomb hitting a target at 900 fps will not penetrate heavy reinforced concrete or any kind of decent bunker (0.5 inch RHA penetration but stopped by 1 inch RHA). It will knock through a house wall, even a foot of basic reinforced concrete (single layer of 2mm steel mesh as a reinforcing), but this will not cut it in the infantry support role. Even a solid dug in bunker made from only wood and dirt will defeat this round.

Add the indirect fire capability of a mortar and you start to see my point.

Nope. Indirect fire capability is more than just a weapon that can elevate high to fire parabolic trajectories. It needs to be incorporated into an artillery net and positioned so it can provide indirect fires. An infantry support vehicle presumably operating at the front lines will not be able to stop its direct fires and shoot indirectly whenever a call for fire comes through. Even if it could in many cases it might not even be able to train onto a target because of limitations in firing arcs. There is a reason why artillery and mortar units are usually located behind the lines: so they can fire indirectly in peace and having firing arcs that cover the areas in which their fires are needed.

There are other flaws in this weapon such as low time of flight meaning unlike a conventional gun it is difficult to engage moving targets at anything above close range without barrage fire. Also a very useful shell for infantry support is canister and I’m not sure if direct fire mortar would provide enough velocity to a canister round to be effective.

120mm breech loaded mortars are not a bad idea to recapitalise mechanised battle group organic mortar capability. But there are still a range of problems in using them to replace tanks as an assault gun, ie infantry support vehicle.

 

[SpudmanWP]

I see your point.. I think I've been out to the turret for too long

 

[MickB]

I’m highly sceptical of this perennial proposal because a 120mm mortar is not an adequate direct fire weapon. While an excellent mortar and PGM firer a horizontal flight path 120mm mortar bomb is not going to knock out any kind of half decent bunker. Or any kind of structure made from reinforced brick or concrete. The mortar bomb wall is just too weak and doesn’t have enough kinetic energy to do anything more than peck at the surface of most direct fire targets.

The best infantry support gun is a tank. It has the armour to take hits and in the case of the 120mm smoothbore gun it now has all the right types of ammunition for infantry support. If you needed a lightweight infantry support gun then a turretless AFV with thick frontal hull armour and a high velocity gun could do the job. You could easily build something like this with an L7 gun with 40 rounds and RPG/23mm AP proof armour (all angle) for around 20-25 tonnes.

As an example of using existing equipment to provide a different capability for the ADF. I wondered if the now replaced Hamel guns could have been fitted to the old Leopards to make a heavy FSV.

Better HE than the L7 gun. Hesh rounds for bunkers. Canister rounds. Gun tube launched ATGWs as emergency defence against tanks.

This frees the M1s to concentrate on anti armour or to strike in mass.

 

[Abraham Gubler]

I see your point.. I think I've been out to the turret for too long

Nah it’s not that. It’s just that there has been such a ‘buzz’ around the internet about the 120mm breech loaded mortar that everyone, myself included, thought it was a good idea. Except the people who build guns and don’t have a mortar to sell. It’s this informed opposition to the mortar as a direct fire weapon is the good reason why no one is building them.

The simple facts that a 120mm HE shell fired by a gun will penetrate 2-3 times as much reinforced concrete as a 120mm HE bomb fired by a mortar. And the mortar’s threshold is below that of the strength of many structures. Like bunkers made from layered logs and dirt, or log bunkers built inside buildings and weight bearing reinforced concrete structures.

 

[Abraham Gubler]

As an example of using existing equipment to provide a different capability for the ADF. I wondered if the now replaced Hamel guns could have been fitted to the old Leopards to make a heavy FSV.

That’s why we brought the M1s. To provide an infantry support vehicle with enough armour to be survivable. Which the Leopard 1 was not considered to be anymore (lack of armour). Also there is nothing the Hamel 105mm in a tank turret can do that the original L7 couldn’t. So it wouldn’t be worth the change. While the HE shell might be marginally smaller the much higher velocity of it fired by the L7 makes the later more lethal. It also has HESH (which isn’t actually that good being fired at bunkers of mixed, layered construction) and Canister rounds.

 

[Volkodav]

I suppose in a light tank there could be an argument that a medium calibre automatic gun 50-75mm firing HV high penetration programmable ammunition in addition to whatever the latest APDS acronym is could be the way to go. The HV round penetrates the structure and then detonates inside. Guided rounds could provide a limited AD capability as well. Mount a couple of ATGMs for dealing with any MBTs that slip through.

 

[kato]

Eh, this is what 120mm low-recoil guns are designed for, like the Giat FER, the RUAG CTG or Rheinmetall's LLR. All of them are suitable for lightweight AFVs, and ammunition development with the same companies recently runs mostly towards infantry-support shells. It's just that no one's buying them. The guns that is. Cuz there's enough proper tanks around to do such jobs where needed.

 

[Abraham Gubler]

Eh, this is what 120mm low-recoil guns are designed for, like the Giat FER, the RUAG CTG or Rheinmetall's LLR. All of them are suitable for lightweight AFVs, and ammunition development with the same companies recently runs mostly towards infantry-support shells. It's just that no one's buying them. The guns that is. Cuz there's enough proper tanks around to do such jobs where needed.

Some of the new 120mm HE rounds are quite impressive. Like the Rheinmetall MP round with the nose cone full of titanium pre formed fragments and the IMI APAM round with the option of the warhead breaking up into four sub munitions for airburst coverage.

There are also the low-recoil 105mm guns firing the same L7 ammo as the pre 120mm generation of tank guns (Stryker AGS). You can also get this gun in the Belgian Cockerill turret (CC-CV) with high angles of elevation (+42 degrees). There are a wide variety of 105mm HE rounds for infantry support. The same turret can also be fitted to a low-recoil 120mm gun and the Koreans have fitted it to their K21 IFV hull for trials.

 

[Dodger67]

I suppose in a light tank there could be an argument that a medium calibre automatic gun 50-75mm firing HV high penetration programmable ammunition in addition to whatever the latest APDS acronym is could be the way to go. The HV round penetrates the structure and then detonates inside. Guided rounds could provide a limited AD capability as well. Mount a couple of ATGMs for dealing with any MBTs that slip through.

Something like the South African Rooikat - but on a heavier tracked chassis?
The current one is 8x8 wheeled - optimised for speed and mobility and not heavily armoured.

Its 76mm gun is based on the OTO Melara naval gun and fires basically the same ammo and Denel has developed a useful APFSDS round for it - effective against T55-class tanks that are still common in most of Africa. Adding ATGMs would be a fairly simple upgrade. An L7 gun is an available option too.

 

[Volkodav]

Something like the South African Rooikat - but on a heavier tracked chassis?
The current one is 8x8 wheeled - optimised for speed and mobility and not heavily armoured.

Its 76mm gun is based on the OTO Melara naval gun and fires basically the same ammo and Denel has developed a useful APFSDS round for it - effective against T55-class tanks that are still common in most of Africa. Adding ATGMs would be a fairly simple upgrade. An L7 gun is an available option too.

Pretty much what I was thinking. It would be interesting if DAVID and/or Volcano rounds / systems could be integrated into an AFV mounted gun to introduce low angle AD and possibly a top attack function against MBTs and other hard targets.

 

[Abraham Gubler]

You’d be interested in the US Army experiments in the 1970s with the ARES 75mm cased telescope ammunition XM274 gun and the RDF/LT. The XM274 could fire around 60 rounds per minute and had an elevation of 45-60 degrees (depending on the turret design). Using the IR prox fused shell of the Naval 76mm Oto-Gun a three round burst was highly lethal against helicopters and attack aircraft. The gun also fired a similar APFSDS round to the 76mm M32 and South African GT4 guns which could perforate a T-55 at the same ranges as a 105mm L7 APFSDS round. With the burst fire option 75mm HE could be highly lethal against infantry and also against reinforced concrete being able to rapidly put round after round into the same hole.

 

[Waylander]

IMHO Kato nailed it.

IF one wants to get a rather light vehicle for direct fire support the 120mm lightweight smoothbore guns are the way to go. You get host of usefull ammunitions (HEAT, programmable HEs, cannister, low collateral damage brittle rods,...) and commonality with your tank fleet.

But why should I use such a vehicle if I can use a real tank (preferable with an urban ops kit fitted)?

Such a vehicle is only interesting for oversea missions where I can't ship them but I am also shy of using plain old light airborn/air assault infantry units. Add to that environments with lots of hard ground to cover and low tech enemy forces (aka South Africa).

So the scope in which such a vehicle is usefull is rather small. That's why proposals like the CV90120T and Centauro120 are not bought.

 

[STURM]

About 2 years ago the Indian army issued a requirement for a wheeled ''tank destroyer'' that can be air deployable, for use in the northern region of the country. Despite its ''tank destroyer'' moniker the vehicle is also intended to be used to provide units with fire support. Not sure what vehicles were offered for this requirement.

 

[Feanor]

IMHO Kato nailed it.

IF one wants to get a rather light vehicle for direct fire support the 120mm lightweight smoothbore guns are the way to go. You get host of usefull ammunitions (HEAT, programmable HEs, cannister, low collateral damage brittle rods,...) and commonality with your tank fleet.

But why should I use such a vehicle if I can use a real tank (preferable with an urban ops kit fitted)?

Well that's what Russian/Soviet force orgs used and use currently, simply a tank btln in the Motor-Rifle brigade/regiment. But western militaries have used things like the Centauro, and the Russian military is moving away from using MBTs like this, potentially replacing them with lighter vehicles.

Such a vehicle is only interesting for oversea missions where I can't ship them but I am also shy of using plain old light airborn/air assault infantry units. Add to that environments with lots of hard ground to cover and low tech enemy forces (aka South Africa).

So the scope in which such a vehicle is usefull is rather small. That's why proposals like the CV90120T and Centauro120 are not bought.

Well the reasoning in the VDV is 1) light weight for air drop capability 2) commonality with their universal chassis (IFV/APC) 3) price tag. Also the VDV never had MBTs to use in this role, and for them this kind of direct-fire support is new. And they were very impressed with the 100mm main gun on the BMD-4 (Bakcha-U module). Their experience in the second Chechen war proved that they needed the direct-fire support. And obviously as long as the air-droppability requirement is kept, for them MBTs are simply not an option.

But my question is then, why are vehicles like the Centauro, or Stryker MGS, or the Russian developments (including 120mm direct-fire guns on Bumerang and Kurganets chassis) being developed and bought, instead of just sticking a btln of Abrams into a Stryker Bde? Mobility and deploy-ability concerns?

 

[FormerDirtDart]

But my question is then, why are vehicles like the Centauro, or Stryker MGS, or the Russian developments (including 120mm direct-fire guns on Bumerang and Kurganets chassis) being developed and bought, instead of just sticking a btln of Abrams into a Stryker Bde? Mobility and deploy-ability concerns?

Deployability and commonality are the reasons for the development of the Stryker MGS .
Remember, the goal of the Stryker was to be C-130 deployable, and having a common chassis was targeted to reduce the logistical load of the brigade. Again, improving deployability of the brigade.