That_Baka

Based on the graphs you posted earlier, the 120 mm DM13 and 120 mm DM23 APFSDS have rather short penetrators, but also a rather large diameter. This is relevant, since penetration increases with diameter for a given length (more accelerated mass = more kinetic energy; penetration scales with kinetic energy). A slightly thinner rod with greater length would overall be superior, but technology and/or other requirements resulted in a diameter of 32 mm for the DM23 APFSDS (thinner tungsten rod with the available alloys did shatter too often).

 
The velocity of the DM23 after traveling 2,000 m is 1,529 m/s according to Swiss firing tables, but these list the muzzle velocity at only 1,640 m/s. So either the DM23 has a muzzle velocity of 1,640 m/s rather than the usually reported 1,650 m/s or the differences are caused by the Swiss measuring methology or are result of a local modification to the 12 cm PzKan 87 (Swiss designation for the DM23). If the latter cases are true, the impact velocity should be ~1,539 m/s instead.
Given that the penetration efficiency of shorter, thicker rods is more, it seems that the DM23 might achieve a penetration per length of above 1 against German HzB A steel:

(from Anderson and Riegel III, 28th International Symposium on Ballistics, "Estimate of penetration/perforation performance based on semi-infinite penetration data")
 
The problem is that exact informations regarding the specific steel alloy are rather scarce. HzB. A (and other steels of the HzB classification) existed in several versions with different alloys and hardness levels. In so far it is hard to convert the exact penetration data into RHA penetration. For the graph from the previous post, the steel hardness was said to be 255 on the Brinell scale.
 
Based on the plotted data, the DM23 might achieve between ~ up to 1.05 P/L, so its 360 mm long penetrator would result in a penetration of 378 mm into semi-infinite HzB. A steel. I don't have access to the source from which the data is taken (research paper by Hohler and Stilp, who apparently work for the German Fraunhofer institute), so it is unknown to me wether the steel target was sloped or not. The penetration against sloped targets would be higher than unsloped ones. As this is semi-infinite penetration, the perforation should be higher (meaning: DM23 would probably punch a hole through a 390 mm thick  HzB. A steel plate under the same conditions).
 
 
As for the 120 mm DM13: It is hard to say due to its unconventional construction. The BM-42 Mango APFSDS (which seems to be the closest thing in terms of internal penetrator construction) supposedly achieves a penetration slightly greater than the combined tungsten penetrator length; it has a higher muzzle velocity, but due to the fin construction a greater V-drop (Fofanov lists V-drop of Soviet 125 mm APFSDS ammo as between 60 and 140 m/s/km; given that Mango has full calibre fins, it should be significantly more than 60 m/s/km). Maybe the steel sheat helps increasing the penetration efficiency by simulating a thicker rod/lower L/D ratio?
 
The DM13 should have slightly above 1,500 m/s velocity at 2,000 m distance according to the US graph from the last post (probably 1,510 - 1,520 m/s). That and its shorter rod should lead to a lower penetratioon than DM23 by quite a bit... how much? I don't know. Maybe it is 320-350 mm, if the steel has any positive effect on armor penetration. Otherwise it would again be close to a P/L of 1 (if DM13 behaves like a conventional monoblock penetrator), which would lead to a penetration of only ~310-320 mm. Perforation and penetration against sloped targets might again be higher.
 
The penetrators of both the M833 and the 120 mm DM23 APFSDS have rounded tips, which performs slightly worse than flat-tipped penetrators against sloped target (but penetration still should be higher than against unsloped ones). 

 
 
Source is a Rheinmetall presentation from 2002. It used to be on DTIC, but I cannot find the full presentation at the moment... maybe the link expired or it was removed...
 
The M111 Hetz was capable of penetrating the original T-72's hull armor at very short ranges (some sources say 500-800 metres maximum). The T-72 had a glacis consisting of 80 mm steel, 105 mm stekoplastika (glass-fibre reinforced plastic) and 20 mm steel sloped at 68°. The T-72A had a different layout: 60 mm steel - 105 mm stekoplastika  - 50 mm steel (this is also 10 mm more steel), which was more effective against AP(FS)DS ammo. On later models, a 16 mm thick steel plate was added to the hull, improving protection further. The late production model of the T-72A featured spaced hull armor.

 
The M111 Hetz could never defeat the turret armor except for maybe a direct hit near the gun mount, where the armor thickness was only ~300-350 mm. The turret reaches a thickness of more than 475 mm at the well armored cheeks.

Dean Speir covered this over at "The Gun Zone" back when it happened in 2001.

Initial Report
https://web.archive.org/web/20160317190046/http://www.thegunzone.com:80/m1akb.html

Shooter's Reply
https://web.archive.org/web/20160315120725/http://thegunzone.com/m1akb/762d2.html

Necropsy
https://web.archive.org/web/20160315121736/http://thegunzone.com/m1akb/762r.html

And there is a livejournal post about AMX-30 test with Radar FCS(in Russian)
https://strangernn.dreamwidth.org/1786004.html
 

Heh, always knew that.

@LoooSeR @EnsignExpendable

 
Edit: I mentioned our resident Russian spies, but for the capitalist pigs, the title of the book reads "girl on the train".

And people thought stepped hulls went out of fashion half a century ago! Hah! (Just... why does this exist in this form...)

300rpm 76mm autocannon
i bet this is how this thing sounds like when it fire
 

Damn Americans can't stay away from our bacon hot dogs!
Just don't get massacred by cocky elementary school children with snowballs....

A perforated armor scheme for use against a long rod penetrator wouldn't work quite the same way as perforated armor screens on APCs work.  Those are mainly to stop 12.7mm and 14.5mm AP projectiles, and the defeat mechanism is often by breaking the penetrator in half.
Against a long rod penetrator the mesh would be designed to take advantage of the fact that LRPs yaw into sloped surfaces:

 
Even a very slight angle of attack of the LRP would enormously reduce its sectional density and make it much easier for the rest of the armor array to stop the penetrator.

I suspect that the metal in the NERA package does make a difference.  The latest M1 variants and IIRC latest T-90s are supposed to use titanium in the fancy tryhard frontal composites.

The full title of this work is "Weaponeering - Conventional Weapon System Effectiveness" by Morris Driels, who teaches at the USN Postgraduate School, and the cover of the edition I have in hand can be seen below.


 
The book aims to "describe and quantify the methods commonly used to predict the probably of successfully attacking ground targets using air-launched or ground-launched weapons", including "the various methodologies utilized in operational products used widely in the [US military]." Essentially, this boils down to a series of statistical methods to calculate Pk and Ph for various weapons and engagements. 

The author gave the book to my mother, who was a coworker of his at the time, and is of the opinion that Driels is not as smart as he perceives himself to be. But, hey, it's worth a review for friends.

I will unfortunately be quite busy in the next few days, but I have enough spare time tonight to begin a small review of a chapter. I aim to eventually get a full review of the piece done.

Our dear friends @Collimatrix and @N-L-M requested specifically chapter 15 covering mines, and chapter 16 covering target acquisition.

Chapter 15
Mines

The mine section covers both land mines and sea mines, and is split roughly in twain along these lines.

The land mine section begins with roughly a page of technical description of AT vs AP, M-Kill vs K-Kill, and lists common US FAmily of SCatterably Mines (FASCAM) systems. The section includes decent representative diagrams. The chapter then proceeds to discuss the specification and planning of minefields, beginning with the mean effective diameter of a mine. Driels discusses a simplified minefield method based on mine density, and then a detailed method.

The simplified method expresses the effectiveness of the minefield as a density value. Diels derives for the release of unitary mines from aircraft

NMines = Fractional coverage in range * fractional coverage in deflection * number of mines released per pass * reliability * number of passes

and for cluster type

NMines = FRange * FDefl * NDispensers * Reliability dispenser * NMines per Dispenser * Reliability Submunition * number of passes

and then exploits the evident geometry to express the Area and Frontal densities. Most useful is the table of suggested minefield densities for Area Denial Artillery Munition and Remote Anti-Armor Mine System, giving the Area and Linear densities required to Disrupt, Turn, Fix, and Block an opponent. 


Whereas the simplistic method expresses effectiveness as a density, the detailed model views the targets and mines individually, assuming the targets are driving directly through the minefield perpendicular to the width and that there is only one casualty and no sympathetic detonations per detonation. The model computes the expected number of targets destroyed by the minefield, beginning with the Mean Effective Diameter and the PEncounter based on distance from the mine. 

Driels derives the number of mines encountered which will be encountered, not avoided, and will engage the target. I can't be arsed to type the equations in full, so here you go.



The section concludes with an example calculation using the detailed mine method. Overall, this shows the strengths and weaknesses of the book fairly well - it is a reasonable derivation of open-source statistical methods for predicting Pk and Ph and the number of sorties required, but US-specific and limited in scope and depth. 

The treatment of Sea Mines  begins by describing the various types and uses of said mines, importantly noting that they have both defensive and offensive uses, and that the presence of the threat of mines is equally important as the actual sinking which occurs. There are three classifications of sea mines, contact, influence, and controlled.

Shallow water mines are treated trivially, considering them equivalent to land mines with Blast Diameter in the place of MED, and assuming that the mines cannot be avoided.

Deep water mines are approached in a similar manner, with the desire to determine the number of mines needed to achieve the required probability of damage, and planning missions from there. Two features of sea mines must be considered, however - mine actuation by passing of the target, and mine damage to the target. The probability of activation is, unfortunately, dependent on the depth of the mine and distance, forming a series of stacked bowls as below.


The mean value of PActivation is the statistical expectation of the curve. Because I don't feel like screencapping another equation, the Width of Seaway where an actuation can occur is qualitatively merely the area under the actuation curve calculated for a specific mine and target combo.

The damage function is also of interest - because we require the mine to both actuate and damage the target, this limits our earlier area under the curve to that area integrated to the limits of the damage function. The selection of mine sensitivity plays a very large role in the effectiveness of our mines. A high setting will lead to many more actuations than damages, which can be indicated by the ratio of the actuation area and the damage area from earlier. Setting the actuation distance equal to the damage distance means that every actuation causes damage, but the probability of actuation is only around 42%. The compromise which selects some Areadamage / Areaactuation of around .8 to .93 is generally preferred. This gives us several useful terms -
PA+D = Reliability * Areadamage / Widthminefield . The probability that the first ship to transit a minefield is referred to as the threat, or
Threat T = 1 - (1 - PA+D)^NMines = 1 - (1 - Reliability * Areadamage / Widthminefield ) which can obviously be solved for NMines to get the desired number of mines for a desired threat level.

Anti-submarine mines are an interesting subset of deep sea mines, as they turn the problem from two-dimensions to three. Driels accounts for this by replacing the mine damage width with the mine damage area, to no one's surprise. Driels claims that the probability of actuation and damage is 

PA/D =  Damage Area / (Width * Depth of minefield). Despite my initial confusion, the reliability term safely reappears in the threat definition below.

T = 1 - (1 - (Reliability * Area damage)/(Width * Depth of minefield))^NMines, with a solution for number of mines for given threat level fairly easily taken out as before.

Lastly, there is a summary of topics for each chapter, though unfortunately they are qualitative descriptions. Including the final derived equations in this part would be a major benefit, but is overlooked. Ah well. They are quite good for review or refreshing the material.

As before, this is a relatively interesting if shallow engagement with the statistical methods to calculate Pk and Ph and the number of sorties required. Going more into detail regarding selecting Threat values or common (unclass) parameters would be interesting, but is lacking. Assuming I don't slack off tomorrow, I should have most or all of the Target Acquisition chapter covered.

guided artillery shell and GLATGMs

The bolt group of this carbine repeats the bolt of the Garand rifle.
 

Thank you for continuing your work in teaching us how to root out Kharkovite saboteurs.

Baller as fuck.
 

T-90MS side turret is actually well protected (at least it is protected, compared to plain steel T-90A turret sides)

I like how everyone believes that bullshit about SDI even though it has no basis in reality:

Kharkov in1980s designed a crew capsule just for 2.
 

 
We know what they will be doing there...
 

Turns out the traditions of tanks in Russia went further back than anyone originally thought.
 

 

The anti-tank pitchfork, three-tined, six-tined and eight-tined varieties, proved completely ineffective.

it gets better every god damn time 

Dragoon is for export, BMP-3 with Baikal turret is probably upgrade package for our Army and for export (maybe). BMP-3 with normal turret have better firepower and selection of weapons.