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17 hours ago, TWMSR said:

Great idea ;) It is so silly to put parasitic mass into design, why do not use zero-mass sabots instead? And why waste so much energy on muzzle blast? All energy should go into penetrator, it must be easy task.

 

I know all about the issues of parasitic mass and the like, 35% just seems to be a very high mass fraction for a modern 120mm (obviously, bore size plays a huge role in 'proper' sabot mass fraction) sabot made using a composite material. Old Soviet 125mm metal sabots had a *superior* mass fraction (approx 30-31%), with a wider bore requiring a larger sabot.

 

For what it is worth, the sabot mass fraction is ~20% of total projectile (Sabot + Rod) mass on 829A3. (Approx 2 kg sabot, calculated from the 4.4kg sabot of 829A1 plus AMPTIAC's numbers of Sabot weight savings generation over generation. 829A2 Sabot was 35% lighter than 829A1's Sabot, and 829A3's Sabot is 30% lighter than A2's.)

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For the mean time:     Updated Special Armor Locations:                            

French 140 mm smoothbore gun firing :      

AMX Leclerc Series 1 Special Armor distribution in the hull and turret (not including the spaced heavy side skirts). Once the model is complete i will use it to do some vulnerability modelling along t

Bore size plays it's role, but double-ramp sabots, developed for high elongation penetrators, needs to be long to properly support the rod during firing. Sabot design is not all about reduction of parasitic mass, it should be light enough, but it has other important tasks. Old Soviet 125 mm metal sabots got it's merits, but using ring sabots and full-bore fins and low elongation penetrators today might be considered as suboptimal.

 

Changing sabot material, as in case of M829A1>M829A2, is one way to go (btw. where did you find information that sabot of M829A3 is 30% lighter than one of shorter's M829A2). The other is novel sabot design. And this is the way that Rheinmetall is said to choose in new developments (DM 73 probably not, KE2020Neo probably yes).

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3 hours ago, TWMSR said:

Bore size plays it's role, but double-ramp sabots, developed for high elongation penetrators, needs to be long to properly support the rod during firing. Sabot design is not all about reduction of parasitic mass, it should be light enough, but it has other important tasks. Old Soviet 125 mm metal sabots got it's merits, but using ring sabots and full-bore fins and low elongation penetrators today might be considered as suboptimal.

 

Changing sabot material, as in case of M829A1>M829A2, is one way to go (btw. where did you find information that sabot of M829A3 is 30% lighter than one of shorter's M829A2). The other is novel sabot design. And this is the way that Rheinmetall is said to choose in new developments (DM 73 probably not, KE2020Neo probably yes).

 

Oh, I am aware of the limitations of soviet APFSDS and Sabot design - it's just that it beggars belief that ye olde soviet metal sabots had a better mass fraction despite the shorter rods and the fin situation. The Soviet ones were not made of a particularly weight-efficient material, having been primarily chosen for manufacturability and durability. I also didn't criticize the 130mm Sabot having such a high mass fraction as that thing is still in development, works at unprecedented pressures, and has a notably wider bore.

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5 hours ago, SH_MM said:

The M829A3 sabot mass is 3 kilograms.

 

I am not sure how to square that with the numbers above from AMPTIAC given the ~4.4kg sabot mass of 829A1.

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10 hours ago, BaronTibere said:

Weren't the old soviet sabots also much smaller because the use of steel for the projectile didn't require nearly as many teeth/groves between the sabot and perpetrator? Seems like a totally irrelevant comparison.

 

Yes, the old ring sabots were a lot smaller due to material choices for the penetrator and the use of full bore fins, but on the contrary they were made usually of mild steel - an extremely weight-inefficient material, and they had to cover a wider bore (so wider if not as long).

 

I would think that the use of mild steel and a wider sabot would more than make up for the sabot length difference, given the strength/weight ratio of laid-up composites versus mild steel.

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TokyoMorose, thanks for that article. If those numbers are correct, level of mass reduction is phenomenal.

 

There are however some points about that. First of all, M829A1 and A2 are very similar rounds, that got very similar penetrators and

hence both uses sabots that are comparable in size. So if A1 sabot indeed weights 4,4 kg and it is stated that A2 sabot is 35% lighter, than it is easy calculation for A2 sabot.   

 

M829A3, on the other hand, is very different animal. It got long rod that is longer than just long ;) If it's sabot is made of aluminium it would be heavier than A1 sabot. This is, probably, why in that article exact wording is 'additional 30% equivalent sabot mass reduction'. It does not sounds so simple like 'A2 sabot is 35% lighter than A1 sabot, and A3 sabot is 30% lighter than A2 sabot'. For me, at last, it sounds more like 'A2 sabot is 35% lighter than A1 sabot, and A3 sabot is 30% lighter than A2-technology level sabot if made for A3 projectile'. This makes calculations a bit more tricky, as we do not know mass of A3 sabot if made in A1-technology (aluminum), of A3 sabot if made in A2-technology (1st gen. carbon composite), and as it was eventually made.

 

The other point now, 30% equivalent mass reduction between A2 and A3 sabots. Damn, how they did that? Both sabots are double-ramp design, A3 probably pinnacle of that design, with no easily visible means to reduce mass other than change of material. This suggest that 2nd gen. laminate of A3 sabot got much lower density - up to 30%. I would love to have a good read about that new carbon composites, anyone?

 

  

 

 

 

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17 hours ago, TokyoMorose said:

I would think that the use of mild steel and a wider sabot would more than make up for the sabot length difference, given the strength/weight ratio of laid-up composites versus mild steel.

 

I don't know if 5mm of extra bore and steel can make up for all this extra volume (excuse the use of steel beasts):

 

Spoiler

670px-3BM-22.png

 

670px-M829.png

 

 

 

 

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On 4/16/2021 at 12:17 PM, SH_MM said:

 

At the current time, this remains speculation. Nexter has not revealed any specific details regarding the ASCALON concept, not even the caliber/bore diameter (Jon Hawkes initially tweeted that it would be a 140 mm gun, but he later corrected this claim).

 

As stated by Nexter, the 10 MJ muzzle energy are achieved at pressures below the current operational pressures of the 120 mm smoothbore gun family.

From Rheinmetall 

https://www.edrmagazine.eu/why-130-mm-and-not-a-bigger-calibre

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13 hours ago, BaronTibere said:

 

I don't know if 5mm of extra bore and steel can make up for all this extra volume (excuse the use of steel beasts):

 

  Hide contents

670px-3BM-22.png

 

670px-M829.png

 

 

 

 

 

See, I have never understood why spool sabots weren't cast (metal) / molded (for a resin sabot) with an internal hollow. APFSDS rounds are quite pricey things, and you would think that the extra cost of making them hollow wouldn't be much compared to the weight savings. In ballistics, much like rocketry, every gram counts.

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The clue seems to be that sabots cannot be considered only or primarly as parasitic mass. Every gram counts, of course, but the most important task of sabot is transfer of acceleration load to projectile, and to do it in such way that would not interfere launching of that projectile and, as result, the bang it would do at the end of it's trajectory.

 

There are many other issues about sabots, also of high importance as a problem of mass, and in many cases interconnected: sealing the bore, stiffeness of sabot, penetrator-sabot interface, ration of bore erosion, risk of projectile balloting, sabot separation. Decreasing of sabot weight must be made with all those mentioned above things in mind. The art of firing a projectile lies in efficiency of terminal ballistics, not pureness of interior ballistics or aesthetics of exterior ballistic.

 

As for hollow design there were many such designs during APDS era. I recall also that 152 mm  APFSDS XM578/XM579 got sabot with hollow area. Some modern sabots got external grooves or ribs that both increase stiffeness and decrease weight. But the limit for that designs remains in material behaviour during very high G acceleration, when any asymetric load could lead f.e. to asymetric sabot separation, which then could ruin accuracy or even cause projectile goes wild.

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