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   TsNIIToChMaSh (part of Rostec) plans to resume work on promising 45 mm caliber telescopic munitions for small-caliber autocannons on light armored vehicles, Buckov said.
   "We also want to decide on telescopic shots of 45 mm caliber. These works, unfortunately, have been stopped. So far, we have not solved the task for a small-caliber gun. The issue is under development," said Bakov.
   To equip the Russian light armored vehicles, either automatic 30-mm caliber guns or 57-mm ACs in combat modules developed by the TsNII Burevestnik (part of Uralvagonzavod) are now being offered. According to Bakov, guns of 45 mm caliber have an advantage over them in the amount of ammunition on board and a more rational ammunition storage.

 

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45 minutes ago, Militarysta said:

 

I don't see pict

 

Any external link pls?

   Reuploaded this picture to imgur, should work now (vk pics are not displayed for some users for some reason)

tVhVR4x.jpg

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I found an interesting doc on DTIC, about the performance of DU alloy, long rod penetrators at high velocity (>2000m/s). 

 

https://apps.dtic.mil/dtic/tr/fulltext/u2/a236191.pdf 

 

in brief, it states DU is noticeably better than tungsten alloy rods below 2000m/s, but above that velocity, their penetration seems to converge (for a given penetrator design).

 

I thought DU performed best at lower velocity, and WHA maintained its performance at high velocity - or, at least, that’s what I heard. Would this mean that if the 120mm L/55 users stopped being hippies and used DU rods, they would have better performance? Is there something else going on (I remember something about DU ‘self sharpening’ at ~1600m/s or below) that makes DU less suitable for high velocity long rods? Is the ‘Ban DU Weapons’ crowd so strong that they can handicap the military of some countries by forcing them to use sub-optimal materials? 

 

 

Also, the Ballistics Research Laboratory has (or had) a 120mm “Double Travel” gun with a barrel length of 9.4m (L/78), and all I want in life is to see that behemoth slapped on a Uralmash-1 (Su-101) like tank, and test fired :) 

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On 5/17/2019 at 6:58 PM, Lord_James said:

in brief, it states DU is noticeably better than tungsten alloy rods below 2000m/s, but above that velocity, their penetration seems to converge (for a given penetrator design). 

 

I thought DU performed best at lower velocity, and WHA maintained its performance at high velocity - or, at least, that’s what I heard. Would this mean that if the 120mm L/55 users stopped being hippies and used DU rods, they would have better performance

 

Yes and no. The problem regarding the supposedly superior penetration capability of DU is largely related to the measuring methodology - I posted about this earlier in the topic. I.e. while the armor penetration is higher (and "penetration" in this case meaning penetration into a semi-infinite target until the rod is completely eroded) the armor perforation (punching a hole through a target) of DU is not superior to WHA, but rather on par. This is related to the "break-out effect", i.e. the fact that steel plates can break apart at the inner side before the penetrator reaches them - this effect is stronger for WHA penetrators, because the rod erodes slower.

 

In the data summarized in this document, there is also another problem: in figure 6 the authors are comparing the penetration per velocity for different rods (i.e. a 730 gram DU rod is compared to data from other tests, using 65 gram DU, 65 gram WHA, 1 kg WHA and 2 kg WHA penetrators, which also happen to have different L/D ratios) - here it is a problem that penetration per length is dependent on various factors, not only on velocity and material:

Hqsv5rJ.jpg

 

Figure 5 is more relevant, as it compares two test projectiles of equal L/D ratio and equal density, hence equal mass. However such dense tungsten alloys aren't used anymore since the early 1980s, as the combination of different mechanical properties of lower density tungsten alloys is better suited for penetration [of complex targets, but apparently also of RHA]. So it is again not a very useful comparison.

 

Here is a comparison of DU and WHA at equal impact energy and L/D ratio of 30, courtesy of W. Odermatt:

 

v_opt.jpg

 

Note that the higher density of the DU alloy means that for a given muzzle velocity, the data for DU is calculated using a shorter & thinner rod.

 

On 5/17/2019 at 6:58 PM, Lord_James said:

Is there something else going on (I remember something about DU ‘self sharpening’ at ~1600m/s or below) that makes DU less suitable for high velocity long rods?

 

I don't think so. DU penetrators have been used at the same velocities as their tungsten counterparts - with the exception of the M829A1 and M829A3/4. The French designed a version of DM43/OFL F1 with a DU penetrator, M829 and M829A2 were used at velocities comparable to contemporary WHA penetrators, the Soviet DU APFSDS rounds and the - supposed - new developments in Russia and China also operate at rather higher muzzle velocities (1,650-1,750 m/s), comparable to what is used for tungsten penetrators.

 

I guess the idea that DU would perform worse at higher velocities is born out of the fact, that having the highest possible muzzle velocity for a given gun/propellant system does not always result in the optimal performance, specifically against more complex targets. While a higher muzzle velocity increases the penetration/perforation per penetrator length, the problem is that for a given barrel length and propellant charge, the higher muzzle velocity has to be achieved by reducing penetrator weight (either using a thinner or a shorter penetrator). Dependening on the mechanical properties of the penetrator material and the target that the penetrator is ought to defeat, it might be a better idea to trade velocity for mass.

E.g. based on a patent from ATK describing a projectile that happens to have identical dimensions to the M829A3 (and the patent images show a design very similar to the M829A3), increasing the diameter of the penetrator from 22 to 25 mm improves the ability to defeat targets protected by heavy ERA by a significant amount, yet increasing the diameter leads to a reduction in muzzle velocity. So what is better? A thinner penetrator capable of defeating more steel armor or a thicker one, that likely offers more performance against targets protected by heavy ERA?

 

On 5/17/2019 at 6:58 PM, Lord_James said:

Is the ‘Ban DU Weapons’ crowd so strong that they can handicap the military of some countries by forcing them to use sub-optimal materials?  

 

There isn't exactly proof that WHA is "sub-optimal" compared to DU, it all depends on the targets and test conditions. As I previously posted, the US Army Research Laboratory has shown in tests with scaled down penetrators, that the perforation of WHA and DU is more or less identical, DU only appears to be superior when testing with the penetration against semi-infinite RHA targets, which isn't that relevant for actual real-life combat. However the whole focus on penetration into steel targets or the perforation of steel targets is rather misplaced, as no modern MBT relies on steel armor anymore. Rheinmetall announced that they do not test their ammunition against homogenous steel targets anymore, unless the customer pays extra. There are a few aspects that should be considered regarding performance of APFSDS against complex targets:

  • Is the penetrator easy to break/bend? If so, the material needs to be changed or the thickness might need to be increased.
  • Does "self-sharpening" (adiabatic shear) matter? The effect occurs during the eroding of the penetrator while passing through homogenous metal targets... does it happen when penetrating composite materials or ceramic tiles? How much does breaking/shattering of parts of the penetrator when being used against spaced armor diminish the effect? Given that modern armor is focused on deforming/breaking the penetrators of APFSDS rounds, the "self-sharpening" might be completely irrelevant for most of the penetration process.
  • What other optimizations have been made to the penetrator to enhance performance? This includes segmented penetrators, special tip constructions, etc. that can massively affect the ability to defeat complex armor arrays.

From what I've read, some of the current APFSDS rounds using WHA are likely to offer better performance/higher efficiency against complex armor arrays, as WHA's material properties are better (it has a higher stiffness, making it harder to break & bend) and there have been more known optimizations (Poland at least has segmented penetrators, Germany is speculated to use them based on patents, etc.).

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WHA's better stiffness also means slightly lighter sabot mass... or it did before the advent of segmented penetrators.  This paper has more.  Note that the paper is very out of date, as it mentions aluminum sabots as being the standard with no immediate replacement in sight.  But it does cover several of the relevant considerations.

 

On 5/21/2019 at 4:43 AM, SH_MM said:
  •  Does "self-sharpening" (adiabatic shear) matter? The effect occurs during the eroding of the penetrator while passing through homogenous metal targets... does it happen when penetrating composite materials or ceramic tiles? How much does breaking/shattering of parts of the penetrator when being used against spaced armor diminish the effect? Given that modern armor is focused on deforming/breaking the penetrators of APFSDS rounds, the "self-sharpening" might be completely irrelevant for most of the penetration process.

 

It almost certainly occurs in complex targets.  It's a function of how the rod material reacts to high rate loading.  The softening of the material exceeds the work hardening rate.  Doesn't really matter what it's smashing into, just that it's smashing really fast.

 

Based on the USAF paper on autocannon ammunition design, I think that DU penetrators are a no-brainer for small-caliber, armor-piercing autocannons.  The degree to which it simplifies projectile design, and the massive increase in behind-armor effect mean it is clearly superior.  I could buy that whether DU or WHA is better for tank ammo hinges on other considerations.

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https://apps.dtic.mil/dtic/tr/fulltext/u2/a139649.pdf 

 

“Fracture behavior of a uranium and a tungsten alloy in a notched component with inertial loading” 

 

Tl;dr, the rear section of a long rod can be damaged during launch, which can be solved by these simple tricks ballistic physicists don’t want you to know about: 

 

1. Increase ‘lug root’ (the zigzag structures holding the sabot to the rod) radius. 

 

2. Move the rod farther forward, relative to the sabot, so less of the rod is behind the sabot. 

 

3. Reduce the stiffness of the rod, especially the parts behind the sabot. 

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18 hours ago, TWMSR said:

Left to right:

125 mm 3BM-15, 120 mm DM 13, 125 mm 3BM-22, 120 mm DM 23, 125 mm 3BM-32, 125 mm 3BM-42, 120 mm DM 33, 120 mm DM 53, 125 mm 3BM-59.

 

bold - not 3BM29? DOI1985?

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