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16 hours ago, Lord_James said:

 

Since you like weird ideas @Toxn, I'll @ you specifically :D 

 

So, with more modern APFSDS having smaller fins that the bourrelet fins of old, couldn't the bore size be reduced for many AP slingers? Reducing the bore diameter (down to roughly 90-95% of the fin diameter, but not to where the fins interact with the tube) might reduce the weight of the barrel, assuming it stays the same thickness, and would definitely reduce the mass of the carrying sabot, meaning more energy towards the penetrator. This might also mean savings to the weight of propellant needed to get a round up to a particular energy, or increase the energy of an already powerful round without increasing the propellant or chamber size. It might be possible to get a 105mm (or less) gun with a thicker barrel and larger chamber that your normal L7A or M68, but slinging full size 120mm (or larger, if the fins fit) sabots at targets. This gun might be somewhat lighter than the 120's, but I don't think by too much. 

 

I'm going to assume I'm not the first person to come up with this, and that there must be problems associated with doing something like this. I'm going to guess there are barrel droop and vibration problems, thought these might be less so than a normally designed gun because I specifically stated that the barrel stays the same thickness as the original gun (read: 120mm L/44) to cope with the (assumed) higher pressures of the larger parent gun. There's also the fact that the HE shells you will want to sling at infantry are also less effective, unless you make the HE abnormally long, which might also have hidden consequences like strange shrapnel dispersion or tumbling or something else you don't want. I'm disregarding HEAT due to it falling out of favor based on greater ERA usage across many combat vehicles, but it's problems would be similar to the HE shell. 

 

Any thoughts from anybody? I'm always open to being corrected and learning real world experience. 

So part of how APFSDS works, at least as I understand it, is that you get to use a larger swept volume of bore to propel your projectile (subject to the usual diminishing returns as you take the concept out to its extremes). So having a bigger bore is positively an advantage from an internal ballistics perspective (rather than a barrel mechanics perspective), and results in more efficient use of propellant. There's also the additional side benefit, as you noted, that a bigger bore means a bigger HE round and better HEAT-FS performance.

 

The testers here are things like the hot 76mm used on the Rooikat or the 60mm used on Chilean Shermans. From what I can find, the round is a comparable size to the 105mm gun, and has comparable APFSDS performance (if a little poorer overall). The gun is actually heavier than the 105mm L7, however, even though it's a nearly a metre shorter. It also seemingly has a longer recoil stroke. From what I can find about the 60mm HVMS, it's significantly lighter than either the 105mm or 76mm, but has an intermediate length. It's also significantly less powerful, clocking in at something like 240mm of RHA penetration at 2000m vs 270 (76mm) or 300 (105mm).

 

So if the trade-off you're willing to make is in the realm of overall dimensions, then going for a smaller bore might be worth it up to a point. It also provides some interesting options, such as the three-round burst for the 60mm gun (before the Chileans removed it). If, however, you have turret space to spare, then a bigger gun seems to provide few downsides. Once again, subject to the spectre of other trade-offs as you reach the outer ends of the performance envelope. 

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Just to look at what different bore configurations can do for you, I used an internal ballistics spreadsheet and mocked up a bunch of guns of different calibres which run at the same pressure (650 MPa) and have the same tube lengths:

 

57mm L66.7: 2.1MJ 

76mm L/50: 3.74MJ

90mm L/42: 5.24MJ 

105mm L36: 7.13MJ

120mm: L31.7: 9.31MJ

 

Using this approach, I can get the performance of the 76mm gun by using a 105mm gun of the same length which runs at a substantially lower pressure (341 MPa, which is achievable using WW1-era metallurgy). The kicker, of course, is that the 76mm projectile and sabot are somewhat lighter than an equivalent configuration for the 105mm: a hypothetical 15:1 soviet-style APFSDS for the 76mm weighs in at 1.38kg for the penetrator, and ~1kg for an aluminium spindle sabot (note: both calculated using another spreadsheet and so are for illustrative purposes only). The equivalent 105mm sabot is more like 2kg. So to get true equivalence in performance, your hypothetical 105mm goes back up to 522 MPa (ie: roughly equivalent to the pressures found on early 125mm guns like 2A26) and a muzzle energy of  5.73MJ.

 

All of which means, again, that the 76mm probably provides a saving in terms of the overall dimensions of the gun and the overall volume of the cartridge. But it also requires a disproportionately higher pressure to achieve the same results. All of which means that, as you hit the limits of your materials and gun penetration, a bigger bore is going to loom larger and larger as a way to get more out of your platform.

 

This, I think, also neatly explains why small-bore APFSDS slingers tend to go into service in less developed countries: a modern, high-pressure 60 or 76mm is perfectly capable of dealing with the T-62s and the like that your opponents will be fielding, so the advantages of a smaller bore are more apparent.

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On 4/18/2017 at 10:58 AM, Militarysta said:

50th shades of the CL 3254M and  M711/8 MK.2 :)

 

Orginall IMI:

 

http://i.imgur.com/ZGC2Mys.jpg

 

http://i.imgur.com/PpyoMLk.png

 

 

 

Indian copy:

 

http://i.imgur.com/mZStjzj.jpg

 

http://i.imgur.com/SnE9AR9.jpg

 

 

Indian: 1st copy:

 

http://i.imgur.com/boo9tZK.jpg

 

http://i.imgur.com/U3BRE1Y.jpg

(on left)

 

 

PpSv97 VETRA (upper one)

http://i.imgur.com/LtxPaqf.jpg

 

 

Serbian clone:

 

http://i.imgur.com/QXjLjeM.jpg

 

 

 

Polish one (PRONIT)

 

http://i.imgur.com/EoHwk4W.jpg

 

http://i.imgur.com/YxB56Q6.png

 

 

 

It's interesting how the same sabot and penetrator can give difrrent values in sevral manufacurer data :)

 

Polish trials shown 520mm RHA on plate slopped at 60@ 

Slovakia shown >550mm RHA

Czeh shown - "more then 500mm RHA"

etc

 

 

 

And next puzzle:

 

"New Nexter 125mm munition APFSDS":

http://i.imgur.com/abOqYm9.jpg

 

Claimed to have up to 600mm RHA (lol, yeh, sure...)

 

And "old" Pakistani POF 125mm APFSDS:

http://i.imgur.com/I0VSM1Y.jpg

 

Looks quite simmilar - is't it?

POF round gave 460mm RAH at 0. so in 60. it will have slighty more then 520-530mm RHA

 

What I would like to add is...

Czech VETRA APFSDS is indigenously made round by Synthesia with 1650m/s muzzle velocity.

Slovak TAPNA APFSDS is also a separate design from the Pronit and the VETRA with its higher 1690m/s muzzle velocity. Its design is visibly different.

unknown.jpg

 

Now from what im suspecting is that Slovak TAPNA and Czech VETRA have the same penetrator, the difference being in their sabot design. the Slovak TAPNA has lighter sabot design thus having better muzzle velocity. I suspect this is the case, so i calculated the Slovak TAPNA penetration with 50m/s drop every 1km. So 1690m/s muzzle is 1590m/s at 2000m. I made sure the penetrator weight of TAPNA is 3.8kg and adjusted the average diameter accordingly.

 

IMG-6054.jpg

 

The result is 540mm (LOS/60) @ 2000m of penetration for TAPNA. If VETRA is identical penetrator with 1550m/s at 2km... That equates to 525mm @ 2000m of rated penetration.

 

As for the old Pakistani 125mm APFSDS... thats the Chinese 125-I APFSDS round

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182748-FA-D175-4-E3-D-BF1-F-D34438-E397-

 

1-A268-D46-A74-C-444-A-8401-DD1-B4-A9-A2

 

Then there is the Chinese DTW-125 APFSDS which is also known as the BTA4. (125-II 'Phase 2' round)

In Chinese strict criteria against pretty high BHN armour at 80% criteria... the rated penetration is

220mm @ 2000m (68.5 degrees) -- 600mm LOS

 

image0.png

[On the left hand side you can see the DTW-125 projectile with fins and behind it you can see cut view inside its case]

 

ED1550-A5-4760-445-A-87-A0-996-A9-FAEB5-

 

Under the green cap we can see the frustum area (still a penetrator)

 

In terms of the internal dimensions this is what I've managed to gather.

Penetrator Length: 600mm
Penetrator Diameter: 22mm
Frustum Length: 46mm
Frustum Diameter: 15mm
Density: 17500kg/m3
Penetrator Mass: 3.9kg (Estimated)
Muzzle Velocity: 1740m/s
Velocity at 2000m: 1640m/s

 

In the same criteria (50% vs 260BHN) - The DTW-125 has a penetration of 620mm (LOS/60) @ 2000m

 

===================

Last but not least... 125-III (Phase 3 Round) which is only compatible to the ZTZ99A.

oghkuhkahkk71.jpg?width=641&format=pjpg&

 

Its officially called DTC10-125 APFSDS and has muzzle velocity of 1800m/s.

 

eJ-Z3-374Wc.jpg?size=405x720&quality=96&

 

On the left its the DTW-125 and on the right we have the DTC10-125. Youll quickly notice that the projectiles look identical, but there are differences. The Chinese scraped every last millimetre of penetration from their 125mm gun and the projectile length.

 

- DTC10-125 penetrator starts from the very top (unlike DTW-125 which has a ballistic cap and a tip)

- DTC10-125 is a Depleted Uranium Rod compared to DTW-125 being Heavy Tungsten Alloy.

- DTC10-125 uses a different improved propellent which allows the heavier projectile (compared to DTW-125) to still achieve superior muzzle velocity compared to the DTW-125.

- It makes DTC10-125 roughly a 635-640mm penetrator x 22mm DU penetrator rod with 1800m/s muzzle velocity.

 

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My personal calculation for DTC10-125

IMG-6057.jpg

 

Suggests 690mm (LOS/60) @ 2000m of penetration

However it should be rather obvious that due to its design, it has no anti era capability.

 

 

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On 11/8/2021 at 4:41 PM, Guest Lix said:

182748-FA-D175-4-E3-D-BF1-F-D34438-E397-

 

1-A268-D46-A74-C-444-A-8401-DD1-B4-A9-A2

 

Then there is the Chinese DTW-125 APFSDS which is also known as the BTA4. (125-II 'Phase 2' round)

In Chinese strict criteria against pretty high BHN armour at 80% criteria... the rated penetration is

220mm @ 2000m (68.5 degrees) -- 600mm LOS

 

image0.png

[On the left hand side you can see the DTW-125 projectile with fins and behind it you can see cut view inside its case]

 

ED1550-A5-4760-445-A-87-A0-996-A9-FAEB5-

 

Under the green cap we can see the frustum area (still a penetrator)

 

In terms of the internal dimensions this is what I've managed to gather.

Penetrator Length: 600mm
Penetrator Diameter: 22mm
Frustum Length: 46mm
Frustum Diameter: 15mm
Density: 17500kg/m3
Penetrator Mass: 3.9kg (Estimated)
Muzzle Velocity: 1740m/s
Velocity at 2000m: 1640m/s

 

In the same criteria (50% vs 260BHN) - The DTW-125 has a penetration of 620mm (LOS/60) @ 2000m

 

===================

Last but not least... 125-III (Phase 3 Round) which is only compatible to the ZTZ99A.

oghkuhkahkk71.jpg?width=641&format=pjpg&

 

Its officially called DTC10-125 APFSDS and has muzzle velocity of 1800m/s.

 

eJ-Z3-374Wc.jpg?size=405x720&quality=96&

 

On the left its the DTW-125 and on the right we have the DTC10-125. Youll quickly notice that the projectiles look identical, but there are differences. The Chinese scraped every last millimetre of penetration from their 125mm gun and the projectile length.

 

- DTC10-125 penetrator starts from the very top (unlike DTW-125 which has a ballistic cap and a tip)

- DTC10-125 is a Depleted Uranium Rod compared to DTW-125 being Heavy Tungsten Alloy.

- DTC10-125 uses a different improved propellent which allows the heavier projectile (compared to DTW-125) to still achieve superior muzzle velocity compared to the DTW-125.

- It makes DTC10-125 roughly a 635-640mm penetrator x 22mm DU penetrator rod with 1800m/s muzzle velocity.

 

DTC-10/125 never utilize a du penetrator, just like every other Chinese sabot

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On 11/8/2021 at 4:41 PM, Guest Lix said:

182748-FA-D175-4-E3-D-BF1-F-D34438-E397-

 

1-A268-D46-A74-C-444-A-8401-DD1-B4-A9-A2

 

Then there is the Chinese DTW-125 APFSDS which is also known as the BTA4. (125-II 'Phase 2' round)

In Chinese strict criteria against pretty high BHN armour at 80% criteria... the rated penetration is

220mm @ 2000m (68.5 degrees) -- 600mm LOS

 

image0.png

[On the left hand side you can see the DTW-125 projectile with fins and behind it you can see cut view inside its case]

 

ED1550-A5-4760-445-A-87-A0-996-A9-FAEB5-

 

Under the green cap we can see the frustum area (still a penetrator)

 

In terms of the internal dimensions this is what I've managed to gather.

Penetrator Length: 600mm
Penetrator Diameter: 22mm
Frustum Length: 46mm
Frustum Diameter: 15mm
Density: 17500kg/m3
Penetrator Mass: 3.9kg (Estimated)
Muzzle Velocity: 1740m/s
Velocity at 2000m: 1640m/s

 

In the same criteria (50% vs 260BHN) - The DTW-125 has a penetration of 620mm (LOS/60) @ 2000m

 

===================

Last but not least... 125-III (Phase 3 Round) which is only compatible to the ZTZ99A.

oghkuhkahkk71.jpg?width=641&format=pjpg&

 

Its officially called DTC10-125 APFSDS and has muzzle velocity of 1800m/s.

 

eJ-Z3-374Wc.jpg?size=405x720&quality=96&

 

On the left its the DTW-125 and on the right we have the DTC10-125. Youll quickly notice that the projectiles look identical, but there are differences. The Chinese scraped every last millimetre of penetration from their 125mm gun and the projectile length.

 

- DTC10-125 penetrator starts from the very top (unlike DTW-125 which has a ballistic cap and a tip)

- DTC10-125 is a Depleted Uranium Rod compared to DTW-125 being Heavy Tungsten Alloy.

- DTC10-125 uses a different improved propellent which allows the heavier projectile (compared to DTW-125) to still achieve superior muzzle velocity compared to the DTW-125.

- It makes DTC10-125 roughly a 635-640mm penetrator x 22mm DU penetrator rod with 1800m/s muzzle velocity.

 

and that 1800m/s velocity has a pre-condition: been fired from a L54 125mm gun. As far as I know, that gun was only tested on ZTZ-99 but never entered service due to reduction on accuracy and issue in quality control.

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On 11/8/2021 at 6:51 AM, Toxn said:

 

The testers here are things like the hot 76mm used on the Rooikat or the 60mm used on Chilean Shermans. From what I can find, the round is a comparable size to the 105mm gun, and has comparable APFSDS performance (if a little poorer overall). The gun is actually heavier than the 105mm L7, however, even though it's a nearly a metre shorter. It also seemingly has a longer recoil stroke. From what I can find about the 60mm HVMS, it's significantly lighter than either the 105mm or 76mm, but has an intermediate length. It's also significantly less powerful, clocking in at something like 240mm of RHA penetration at 2000m vs 270 (76mm) or 300 (105mm).


Do those guns have the same propellant load as the normal L7? I would think squeezing the round down would necessitate lengthening the cartridge, which isn’t preferable to reducing the size of your tank, or necking it down significantly. 

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10 hours ago, Lord_James said:


Do those guns have the same propellant load as the normal L7? I would think squeezing the round down would necessitate lengthening the cartridge, which isn’t preferable to reducing the size of your tank, or necking it down significantly. 

I'll have to check, although there aren't great sources online as far as I know.

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On 11/20/2021 at 8:09 AM, Toxn said:

I'll have to check, although there aren't great sources online as far as I know.

Having had a look at the performance of the rounds, it looks like the propellant loads would be quite different for each round. The 60mm needs around 1.9dm3 of case volume for the propellant, the 76mm around 4.3dm3 and the 105mm around 7.1dm3.

 

This means less than you'd think in terms of the space that the rounds take up, though, since volume scales cubically. As a toy example: a conservatively bottle-necked case for the 60mm (1/3 larger base than tube diameter) would have to be something like at least ~450mm long, an equivalent case for the 76mm would be ~630mm long, and the 105mm would be ~600mm long.

 

The ease of handling of a round is more or less a function of the case length and weight (with weight being one of those factors that becomes exponentially more of a hassle as it increases). So I'd say that, within a certain floor of effectiveness and ceiling of round mass and size, your operational requirements will probably determine where on the graph of size/weight and effectiveness you land. For instance: the 25% jump in penetration performance from the 60mm to the 76mm at the cost of a 40% increase in case length is a decent trade-off if stowed ammunition and rate of fire is worth trading. As is the 30% jump from the 76mm to the 105mm (at the cost of something like a 70% increase in weight), if you need the extra effectiveness against more modern armour.

 

Again; I'm getting the impression that small-bore APFSDS slingers show up more in second and third-tier armies because those are the forces where the floor of effectiveness is lowest. Zapping T-55s and T-62s instead of T-64s and T-72s just gives you a lot more leeway when it comes to choosing what other trade-offs are worth it. 

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1 hour ago, SH_MM said:

This is from a 2013 even held by the Verein Schweizer Armeemuseum. The man in the photo is Walter Lanz, who some may know from the Lanz-Odermatt formula.

 

https://www.armeemuseum.ch/thuner-schiessplatz-anekdoten-rueckschau/

Many thanks for your quick reply. Very interesting for the today's 130mm / 140 mm discussion!

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SIplpMJ.png

 

The RARDE 110 mm (Short) gun, also known as the EXP-7 fired its APDS at a muzzle velocity of 1387 m/s with a velocity drop of 62 m/s at 1000 m.

At this range it was able to penetrate a 152 mm armor plate sloped at 60° and thus the NATO heavy single target.

 

For comparison, the L15A3 APDS fired from the larger L11 120 mm tank gun of the Chieftain main battle tank had a muzzle velocity of 1370 m/s with a velocity drop of 60 m/s at 914 m and was able to penetrate, at this range a 150 mm armor plate at 60° (likely the NATO heavy single target).

 

In spite of its slightly smaller calibre, the EXP-7 could penetrate as much, if not more, armor than the 120 mm L11 tank gun.

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