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6AKwsfK.jpg

 

Orginally polish second generation 120mm APFSDS-T ammo:

 

The designing of a new kinetic energy projectile for LEOPARD 2 tank 120 mm gun started in 2016. Development of a new kinetic energy projectile with a penetrator of boosted efficiency (by ca. 20% than currently manufactured ammunition) for piercing the RHA plate was the main goal of the project.  New generations of tungsten based


sinters with better mechanical characteristics were used to prepare the new design of the kinetic energy projectile, having a lower diameter and a length increased by
ca. 100 mm in comparison with projectiles currently manufactured and supplied to the army, under the procurement contracts for 2014-2017.

(...)

 terminal ballistics show that penetration depth of RHA plate is above 600 mm for the distance of 2000 m

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On 5.4.2018 at 9:24 PM, Ramlaen said:

According to CTA International their CT40 APFSDS will defeat 140mm of RHA at 1500m.  There is also an AHEAD style kinetic airburst to go along with their HE and HE airburst rounds.

 

Forgive me if this is old info and I was simply unaware.

Old news indeed. You shall perish!

 

Seriously though, does anyone with relevant knowledge on the topic can tell me what exactly is blocking the implementation of CTA technology into broader applications? The British, French, and Chinese seem to go ahead with this technology. About the UK there's no debate, but if the French and Chinese are doing something like this, surely it has some clear merits. 

What is blocking its implementation in high caliber (105mm-130mm) guns for tanks, or even small arms? Seems to conserve quite a bit of space for ammo, eases logistics, AND seems to get more penetration overall. 

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6 hours ago, Mighty_Zuk said:

Old news indeed. You shall perish!

 

Seriously though, does anyone with relevant knowledge on the topic can tell me what exactly is blocking the implementation of CTA technology into broader applications? The British, French, and Chinese seem to go ahead with this technology. About the UK there's no debate, but if the French and Chinese are doing something like this, surely it has some clear merits. 

What is blocking its implementation in high caliber (105mm-130mm) guns for tanks, or even small arms? Seems to conserve quite a bit of space for ammo, eases logistics, AND seems to get more penetration overall. 

 

I doubt it would improve large-caliber guns much.  I explained this a while back:
 

 

 

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IMO the marketing for the CT40 gun is rather dishonest when they point out how short the cartridges are without mentioning how wide they are.

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I see now that the old link is gone, victim of the dreaded link rot.  So I will have to explain this all again.

 

Telescoped ammunition, like the way the G11's ammunition was constructed with the projectile buried in solid-cast propellant:

7BALMgu.png

Barely works for small arms and works less and less well as it is scaled up.

 

For any gun to work well the bullet has to seal with the bore and prevent gas from flowing past the projectile.  Gas that flows past the projectile and up the bore causes greatly accelerated bore erosion, and reduces performance because not only is that gas no longer behind the bullet to push it, but the gas is contributing the pressure in front of the bullet, which partially counteracts the pressure behind the bullet.

 

For normal, boring, conventional, functional ammunition, this is not a problem.  All the propellant is behind the projectile, and the surface of the projectile that seals the inside of the bore is jammed into the bore or very close to it.

 

5iEReZ0.png

 

No muss, no fuss.

 

But look at that G11 ammunition again.  The bullet is buried in the propellant.  More importantly, the full caliber part of the bullet that seals the bore is sitting behind the propellant, and a long, long way from the bore.  In order to seal the bore, the entire bullet is going to have to jump about half of its entire length before any of the propellant gas can get around it.

 

The telescoped ammunition is usually designed with a booster charge that breaks up the propellant and helps start the bullet down the bore, but in practice some of the propellant gas will make it around the bullet before it can seal.   As the design is scaled up, this problem gets worse and worse.  The inertia of the bullet scales with the cube of caliber and the distance it needs to travel before sealing is achieved scales linearly.  The amount of force at the base of the bullet only scales at the square of caliber, so it will take longer and longer for the bullet to jump a greater and greater distance, which means more time where the propellant is burning and simply going around the bullet and out the muzzle instead of pushing the bullet.

 

Large-caliber telescoped ammunition, such as the 25mm GAU-7 intended for the F-15, is complete garbage and burns the barrel out in a few hundred rounds, as well as burning much more propellant for the same ballistic performance as conventional ammo.

 

And like I said, if you look at a cross section of the new 40mm CT, they get around this problem by not actually being telescoped.  There is no propellant in front of the sealing ring of the projectile.  This sidesteps all the technical problems of telescoped ammunition, but it also means that the round enjoys no greater volumetric efficiency than conventional ammunition.

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21 minutes ago, Mighty_Zuk said:

So then, what are the advantages of their design? Surely they had some reason to go for CTA rather than the existing Bofors 40mm guns.

 

Well even if they aren't true telescopic ammo, aren't they still somewhat more compact than regular ammo for a given rod length (taking the APFSDS as a reference)?

 

I mean the rod isn't completely buried into the propellant, but probably still more than with a regular ammo design.

 

5olwTwl.jpg

 

A sort of middle ground between the two?

Keeping the bottleneck of the case but inside the outer shell as opposed as a separate piece.

 

Another though, would it be possible that the bottleneck inside the CTA 40 only last for a short time (like it would melt or would be destroyed by the pressure), just long enough for the projectile to get an head-start on the expanding gas (hence the debatable denomination of telescoped).

Just asking.

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2 hours ago, Mighty_Zuk said:

So then, what are the advantages of their design? Surely they had some reason to go for CTA rather than the existing Bofors 40mm guns.

 

The autocannon breech and ammunition feed are both considerably less intrusive into the turret:

ZtebJV5.png

 

SE26x01.png?1

 

The cannon feeds through the trunnion, so the feed mechanism doesn't need to rotate with the cannon and can be pushed all the way to the front of the turret wall.

 

I'm not sure how well this design would scale up.  Certainly an MBT main cannon would present some serious problems, like the fact that the trunnions are buried in the frontal armor package.

 

The ammunition is somewhat more space efficient than 40mm L70 Bofors.  The outside diameter of the 40mm CTA is the same as the rim diameter of the L70 ammo, but the case only about 70% as long.  Ballistic performance somewhat favors the CTA.

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2 hours ago, Ramlaen said:

So the cased in cased telescoped refers to the propellant not protruding in front of the projectile?

 

Cased in this instance means not caseless.  There's a... I think it's polymer and metal, mixed contruction case keeping everything together.  The old G11 ammo was just a blob of propellant with the bullet, primer and booster inside.  The 25mm ammo for the GAU-7 was, if I'm remembering this correctly, of an absolutely bizarre configuration where each round was coated in a waterproof/fire resistant coating that was shucked off like a corn husk before each round went into the firing chamber.  

 

The "telescoped" is nearly meaningless, but it's basically the same configuration as the Textron small arms rounds that are also called "telescoped" even though they don't have any propellant ahead of the projectile either.

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30 minutes ago, Collimatrix said:

 

Cased in this instance means not caseless.  There's a... I think it's polymer and metal, mixed contruction case keeping everything together.  The old G11 ammo was just a blob of propellant with the bullet, primer and booster inside.  The 25mm ammo for the GAU-7 was, if I'm remembering this correctly, of an absolutely bizarre configuration where each round was coated in a waterproof/fire resistant coating that was shucked off like a corn husk before each round went into the firing chamber.  

 

The "telescoped" is nearly meaningless, but it's basically the same configuration as the Textron small arms rounds that are also called "telescoped" even though they don't have any propellant ahead of the projectile either.

 

One more question. Would the cased telescoped design handle chamber pressure better than a traditional design, similar to what Sturgeon described for Textron’s CT rifle?

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8 hours ago, Alzoc said:

 

 

Another though, would it be possible that the bottleneck inside the CTA 40 only last for a short time (like it would melt or would be destroyed by the pressure), just long enough for the projectile to get an head-start on the expanding gas (hence the debatable denomination of telescoped).

Just asking.

 

It might be that the bottleneck in the CTA is designed to be disposable.  The portion of the bore closest to the burning propellant usually takes the most damage, so if the cartridge case takes some of the damage instead of the bore throat, it could allow higher propellant burn temperatures without sacrificing barrel life.

 

But it's hard to say for sure from the information that I have if that's what they're trying to do.

 

1 minute ago, Ramlaen said:

 

One more question. Would the cased telescoped design handle chamber pressure better than a traditional design, similar to what Sturgeon described for Textron’s CT rifle?

 

I would need to see more of the exact design of the firing chamber to say for sure.

 

APysVCi.png

 

The design does have the advantage that it has no exposed case material, while the rimless ammunition used in small arms has a fair amount of exposed area.  The rimmed ammo used in tank guns has close to no exposure though, so the so-called "cased telescoped" ammunition only enjoys an advantage vs. small arms ammunition in that respect.

 

The CT ammunition has the disadvantage that the cartridge case is completely cylindrical with, so far as I can tell, no taper to aid in extraction.  That could make getting the rounds out of the chamber at higher pressures harder.  On the other hand though, they are being pushed out of the chamber rather than pulled, and that may be a more positive way to get the spent case out.

 

From what I've read about the development of the British 110mm gun, the extremely high pressures required by tank guns necessitate a caseless or semi-caseless ammunition design.  The peak pressure is simply so high (120mm APFSDS peak pressure is about double that of rifle ammunition) that a conventional metal case will try to weld itself inside the chamber, and extraction becomes too unreliable.

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The CTA looks more an evolution of the H&K G11's rotating chamber concept than the LSAT LMG actually does, even though the latter is supposed to directly draw from G11's lessons (though I believe Textron primarily paid for the caseless ammo technology rather than the gun internals' patents, seeing that the LMG's rotating chamber is a bit different from the G11's --- as seen at 1:23 in the video below).

 

Spoiler

 

 

 

Dunno whether Textron's design, scaled up to AC size, would be better. At least the ammo wouldn't be forced to pass through the trunnion and it might be a bit easier to switch calibers without changing too many components (barrel and feeding system excluded).


EDIT: Didn't realize someone had posted the same video in the Small Arms thread - this is maybe unnecessary/redundant. :-/

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The HK G11 had a lot of specific technical solutions to problems that came up from the fact that it didn't have a cartridge case.  I'm thinking specifically of the propellant chemistry, which was quite different than conventional ammunition.  From what I've heard, they were still a long ways off from a completely practical weapon, but they got much further than anyone else ever has.

 

@Sturgeon knows more about the development of the G11 and Textron guns.

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