Bronezhilet

Halving the available reaction time and the actual intercept time is pretty huge. Especially since, as you already pointed out, it isn't easy to degrade a penetrator's effectiveness, but it is possible. The most common method (and to be honest, its the only feasible method at the moment) is to introduce yaw in the penetrator by having an explosion push on the stabilising fins. And since the thing is moving at ~1500-1600 m/s, you don't have that much time to actually do so.

The program name is SPEED and is a multi-material Eulerian / Lagrangian hydrocode with explicit solver technique.

Oh boy, we already had Uralvagonzavodskis vs Kharkovites, now we got KMW vs IBD as well? Nice!

New here, but I've followed this thread (and Mech Warfare) for a good while.
 
I attend the United States Military Academy and it is branch week here. Armor brought an M1A2 SEPv2 which, while awesome and cool to get inside of, was nothing new. However, they had a cutaway of a M829A4 round, which was on public display so it's not breaking OPSEC. Thought it would interest you guys.
 


 
Edit: I have no official measurements but I've looked at some photos of M829A3 and the penetrator definitely seems longer based on the sabot petals seeming to be longer at the top.

On this day, 15 years ago.

 
 

 
 
 

 

   Leonid Rashal (very well known doctor) in Beslan, Sept 1st/2nd.
 

   Ruslan Aushev walking to school
 

 

   Gym - in the middle, workshops - on the left, Acting hall - left, near corner of building, library - right side.
 
 

 
 

 
 

   FSB unit "White coal" from Essentuki
 
 
 

 

 
 
 

 

 
 
 

 
 
 

 
 

 
 
 

 
   NSFW
 
 

 
 
 

 
 

   After operation.
 
 
   Soldiers that died during those events:

 
   1. Dmitry Razumovsky ("Major") - lieutenant colonel, head of the Directorate "V" of the TsSN of the FSB of Russia. He was awarded the star of the Hero of the Russian Federation (posthumously). During assault killed 2 terrorists that were shooting at fleeing hostages. Was killed during room-to-room combat inside of the school.


 
 
2. Alexander Perov (“Pooh”) - Major, Head of the Task Force of the 1st Division of the Directorate “A” of the TsN FSB of Russia. When the brutal battle suddenly began on September 3, 2004, Alexander Perov, acting decisively and courageously, personally destroyed one of the four bandits who fired at the hostage children. During combat inside of the school, Major Perov was covering special forces group, but suddenly a terrorist appeared from the opposite side and opened fire in the back of the officers. He destroyed terrorist, but he himself was mortally wounded. He was awarded the star of the Hero of the Russian Federation (posthumously).
 

 
 
3. Oleg Ilyin (“Skala”/ "Rock") - lieutenant colonel, head of 4th fireteam of 3rd department of the Directorate “V” of the TsSN FSB of Russia. Initially acting in the schoolyard, Oleg Ilyin with his subordinates diverted the fire of terrorists who shot at the escaping hostages. In this battle he was wounded, but remained in action. Then he burst into the school building, where he discovered another group of terrorists ready to break out of school. In a fierce battle with point-blank fire, he destroyed two militants. Distracting the attention of the bandits on himself, he saved the life of the soldiers following him and ensured by his actions the complete destruction of this group of terrorists. In this battle, Colonel Ilyin was killed. He was awarded the star of the Hero of the Russian Federation (posthumously).

 
 
4. Andrey Turkin ("Cherkess") - lieutenant, operative of the 2nd department of the Directorate "V" of the TsSN FSB of Russia. Andrei Turkin, as part of his unit, burst into the school building under fire of militants. He was injured, but did not leave the battle. Covering the hostage rescue with fire, he personally destroyed one terrorist. When one of the terrorists, hiding in the pantry, threw a grenade at the hostages, the officer rushed and covered grenade with his body. He was awarded the star of the Hero of the Russian Federation (posthumously).

 
 
5. Mikhail Kuznetsov ("Domovoy") - FSB major. During the special operation, he evacuated more than 20 wounded hostages, mainly children. Covering his group, Mikhail joined the battle with two terrorists and, having destroyed them, died. Order of Merit for the Fatherland, 4th class, with swords (posthumous).

 
 
6. Vyacheslav Malyarov (“Malyar”/"Painter") major, senior detective of Department 1 of Directorate “A” of the CTsSN FSB. During combat inside the building, he blocked the direction of the fire, which was carried out by four bandits in direction of room with the hostages. Having been mortally wounded, Vyacheslav continued to fight, wounded two terrorists and forced them to retreat.
   Cavalier of the Order "For Merit to the Fatherland" IV degree with swords (posthumous).

 
 
7. Andrey Velko - Major, employee of the Directorate “V” of the TsSN FSB of the Russian Federation. As part of the assault group, he entered the school building. Destroyed one of the Basayevites and ensured the actions of the group. Then he came into fire contact with another terrorist and destroyed him. The officer received multiple fatal injuries, covering hostages. Posthumously awarded the Order of Merit to the Fatherland, IV degree.

 
 
8. Roman Katasonov - major, senior operative of the 4th department of the Directorate “V” of the TsSN FSB of Russia. Major Roman Katasonov during the assault penetrated the building and destroyed two terrorists. In one of the rooms he found two hidden children. Rescuing them and covering up the assault group's employees, Roman was fighting with a terrorist's machine gun crew and was mortally wounded.
   Cavalier of the Order of Merit to the Fatherland, IV degree, with swords (posthumous).

 
 
9. Denis Pudovkin (“Gusar”) - ensign, senior instructor of the 3rd department of the Directorate “V” of the TsSN FSB of Russia. He destroyed one of the bandits who was shooting at the children. He carried wounded schoolchildren under fire. Having received a shrapnel wound, he continued to save people. Cavalier of the Order "For Merit to the Fatherland" IV degree (posthumous)
 

 
 
10. Oleg Loskov - ensign, senior instructor of the 1st department of the Directorate “A” of the TsSN FSB. As part of an assault group, he encountered four bandits trying to escape from the school building under the cover of fleeing hostages. He wounded one of the terrorists and, obscuring the hostages, blocked the bandits from escaping. Having been mortally wounded, Oleg continued to support the actions of the assault group with fire. He was awarded the Order "For Merit to the Fatherland" IV degree (posthumous).

   In Beslan
 
 
 

If they consider themselves vessels, I suggest they should be decommissioned and sold for scrap. You can do that with US vessels, can't you?

Jagdpanzer IV/70(A).  Not a lot of wartime pictures of this where it's not blown to smithereens or captured. 
 

 

 

AAV-P7A1 CATFAE (Catapult launched Fuel Air Explosives).  Troop carrying capabilities were exchanged for 21 fuel-air ordnance launchers for the purpose of clearing minefields and other obstacles during an amphibious assault.
 

This concrete cross in the middle of the Arizona desert is mute testimony to the American spirit of can-do and getting things done, even if it's hard.
 
In the 1950s, the United States had taken upon itself the essential task of spying on the Soviet Union.  Why the hell they wanted to spy on a bunch of miserable commies waiting around in bread lines is beyond me, but the point of this story is that Americans can do anything they set their mind to, regardless of whether it's a good idea.
 
To this end the US contracted Lockheed to design the elegant U-2 spyplane.  This worked for a while, but eventually the damn commies developed a habit of shooting these things down.
 

 
Clearly, the commies weren't going to make it easy to spy on them.
 
The solution was to put the commie-spying-on camera on a platform that was both unmanned and in space.  To this end, the Corona satellite family was developed:



There was just one problem; while the astrogation systems (star trackers that could keep the satellite pointed at Earth), calibration systems (the big concrete crosses the satellites could focus on), and launch systems were all mature, digital communications had not yet been refined to the point where the satellites could beam over the images as a series of radio signals.  Film images from the satellites were printed on physical film.  The solution?  Shoot the film canisters out of the satellite and catch them mid-fall with a cargo plane.  Seriously:


 
These two films describe the process in more detail:
 
 
 
Eventually, high-bandwidth radio communications would be developed which would obviate the need for the mid-air snatch operation.  This was significantly less awesome, but also much more practical.

Very interesting vehicle with impressive UFP LOS armor thickness even at preliminary project stage

OBM vol.3 p.342 says it was able to withstand some 122mm KE round, and provided protection against 600mm CE.
The thing is - there is a difference between drawings of preliminary project (p.227), and another drawing (p.341), with later having more sloped armor at around 74 degrees

which leads to even more impressive LOS thickness of 90,7 cm,
however I wish there was some better source for that than my measurements using those drawings scaled by their T-64 type roadwheels and 5TDF engine.
 
...
This thing also had sight cover doors, unlike some other russian vehicles of not-so-distant-past:

...
It also had some sort of periscopic device for commander (which, obviously, was located in hull and had rather limited observation via perisopes in his hatch)
here, protruding on the starboard side of the vehicle:

inside:


Upd:
btw, btvt.info's web version of OBM vol.3 article on 287 has same image in somewhat different quality. Upscaled:



And another thing i should've remembered earlier. Btvt.info's article on soviet ERA development history, among other things, talks about ERA which was tested in 1968 with 3 vehicles in mind - obj. 434 (T-64A), obj 775 and obj. 287. For some reason i've always forgot about 287.
Anyway, that article has this drawing of 287 ERA UFP (as anyone can see,  in very bad quality):

and it says that shape of composite armor UFP+LFP is also shown, and that it was taken from drawing of obj.287-50-assembly2. And that this ERA-hull configuration was tested against Falanga ATGM (IIRC 500mm CE) and was also able to protect against up to 800 mm CE treats. (Which leads to a question of whether composite armor version was tested, and able to withstand, against same treats or not)
Anyway, it shows that angle in question is 75 degrees,
and that alone would lead an UFP of 90+130+30mm to having a LOS thickness of about 96 cm.


...
Another interesting feature of 287 is that people in 1940s-1960s were not satisfied at all 
with the way all that slat armor and other means designed to increase standoff distance from shaped charge weapons
also increase vehicle's dimensions and could be torn away by obstacles.
So both in US and USSR there were some developments on how to fold those things when there are no imminent danger. Gill armor on T-72 is rather well-known, and described there https://thesovietarmourblog.blogspot.com/2017/12/t-72-part-2-protection-good-indication.html in length (in part "GILL ARMOUR")
but there were other things which were proposed, tested, and apparently rejected - and 287 got two of those.

There were some thin presumably metal sheets which look similar to some of the prototypes which were tested in early 60s and later apparently lead to "gill armor"


and even earlier 287 had some netted armor - made using steel wire -

which by the way was also proposed for preliminary project of Obj. 432 in 1961

 

Possibly last post dedicated to the fortification but a very long one dedicated to the heavy fortifications. I hope that a lot of those peculiar details are new for you. Most of the info comes from very knowledgeable staff of heavy infantry casemate N-S-82. If you ever want to visit some object of Czechoslovak fortification system you must not miss this one because this is the only one fully equipped as it shall have been (in fact it's a bit better equipped than in September 1938 then it was not totally finished inside). All photos are from my phone (it's allowed to take photos inside). 
 
N-S-82 is a stand alone infantry casemate located in a line on a slope upon the border crossing Náchod-Běloves. It was built in 1938 in a resistance class II. Which means that it had 2,25 m thick frontal wall (with a stones and earth cover). The roof was 2 m thick and the side and rear facing walls were 1 m thick. The border crossing is down bellow while roughly 1,5 km away on the hill there is an artillery fortress Dobrošov. It was guaranteed to withstand 240 mm artillery shells and 250 kg bombs (according to many authors Luftwaffe had no 500 kg bombs fielded at September 1938 yet) however during weapon testing on a casemate Jordán (experimental one used for fortification and weapon development) which had same resistance class even 305 mm heavy mortar hit didn't penetrate the roof (there were volunteers inside during the test fire!). It is said that there was some damage to the equipment but I don't know more details. 
 
On the same picture you can see also a combined anti-tank/infantry obstacle made of steel U-shape profiles welded together and stuck in a concrete base. Behind them there is anti-infantry barbed wire and a line of steel hedgehogs. Anti-infantry barbed wire could have been placed also in front of those rods. At certain place with high danger of tank attacks concrete anti-tank moats wete built too (sometime they can still be found). 
 
 
In 1938 you could find also these older concrete hedgehogs in the area. Those were used only earlier because they had two importnat drawbacks. The first one was that they offered better cover for the attacking infantry and the second was that their large area made them easier to move by shockwaves from artilery. 

 
A historical image showing how such line looked like in the September 1938 (where it was finished). This picture shows a heavy object K-S-35. 

 
N-S-82 was armed with one 47 mm AT gun, 5 HMG and 5-6 LMG. AT gun with coaxial HMG and a twin HMG were pointing down the valey towards the border crossing. On the opposite side (uphill) there were two single HMGs. LMG were used only in observation cupolas and for close defence of the object (normally the priority was to defend the neighbouring object with primary weapons). 
  
 
Let's go inside. There are three door covered by 2 LMG fire posts and one fire post for personal weapons directly in the entrance which alone had S-shape to prevent any direct fire into the object and on the main door. The first cage door are 200 kg heavy and on the left side behind them there is a fresh-air intake. On the right side there is armored door 600 kg heavy. Behind another corner there is third presurrized door 450 kg heavy. Both heavy door had emergency hatches in them so that the crew could get out if the door were deformed and stuck. 

 
The casemate has two floor. The top floor is combat and the bottom one is technical and living one. Every single heavy object had its own water source which must have been able to deliver at least 1,5 litres per minute. In this particular case it was around 4 litres per minute.

 
This is the electric generator which was pretty noisy. It's in fully working state. It's cooling was used for heating the interior but even in summer the inner temperature didn't get upon 17°C and the soldiers often suffered from respiratory or rheumatic issues. 

 
This is the filtering and air venting room. On the left side there is the ventilator with back-up handles for manual operation (I tried it myself and it's quite tough). On the right side there are filters which were used only in case of gas attack. The whole object had an overpressure in it which was used also for extracting the fumes from gunnery rooms. 

 
This particular object had 32 men crew (only the commander was an officer). The soldiers had one bedroom (see bellow). The sub-officers had their own room with own bed for each one and the commander had also his own room but located on the combat floor. Only Czech or Slovak nationals were allowed to serve in the permanent boarder units manning the heavy fortifications (no German, Poles or Hungarians because low loyality was expected with them). 

 
This is part of the bathroom (it's difficult to take some photos inside because it's quite cramped and I don't want to post gazillion of photos, rather only millions). The lavatories had a water filtration station used to prevent pollution of the main water source and a ventilation preventing methane acumulation). 

 
Down bellow there was also a food storage, hand granade storage (275 pieces) and a telephone room (on the picture). The bunker had several external telephone lines leading to the neighbouring objects and to the sector command post. As a backup a ground telegraph was used with cable antenas dug underground. Depending on the particular soil composition it was capable of morse communication to the range of 5-10 km. Ground radio antenas for voice communication were not installed by September 1938 (the radio was developed and tested but not fielded). 

 
Here you can see some internal communication means in the gunnery room. A simple speaking tube and a telephone. 

 
There was another way how to communicate between the observation cupolas and the gunnery rooms and that was a color code (in case of big noise from bombardning for example). 

 
With that we got onto the combat floor. This is the LMG firing post for the defence of the rear side. You can see observation insert on the left side which was interchangeable with the LMG. The LMG is vz.26 which I don't need to introduce to you for sure. There were 120 ready-to-fire magazines for each LMG in the object! 

 
Here is similar firing post with the observation insert mounted and a removable periscope to the right side of it. That was used to observe the close surroundings and the moats at the weapons. Under the periscope there is a tube for hand grenades used for close defence. 

 
A view inside the observation cupola from bellow. The very peculiar thing here is that the floor worked similarly to the office chair and the soldier could very simply adjust the floor position to his height. The middle column was also used for evacuation of spent cartridges. The cupola is made of 200 mm thick cast steel and the inner diameter is 1,35 m. 

 
This is a periscoipe which could have been errected through the cupola roof for 360° observation.

 
A simple lift was used to transport LMG mags to the cupola.

 
Some more details before we get to the main weaponry. These are JIGs for MG loading. Top is belt-loading JIG for HMG vz.37 and bellow is a one for mag loading of LMG vz.26.

 
This is the kitchen, gentelmen. Yes, for 32 people! The bunker had food reserves for 14 days but I can hardly imagine to fight 2 weeks inside without getting crazy. 

 
This is one very peculiar detail. When the bunker was bombarded by heavy weapons the ceiling could elastically deform. To prevent internal much thinner walls from collapsing they had on top of them a cork layer which worked like a spring reducing the pressure on the walls.

 
Except for the grenades all ammo was stored in the combat department close to the weapons. The capacity of this object was 600 47 mm shells and 600 thousand 7,92x57 rounds. Now imagine that 263 heavy and nearly 10000 light objects were actually built before Münich. What an insane amount of ammo stored in the fortification system!  In reality around 3/4 of the ammo was delivered at 28th September but I would say that it's still huge achievement of the army logistics. On the picture you can see AP and HE-FRAG round of the AT gun (from later war production). A third anti-infantry round was being developed but wasn't fielded. I don't know how it's called in English when the round is filled with steel balls. Can you help me?  

 
This is the right gunnery room with two single HMG vz.37 and one LMG vz.26 for close defence. Notice that all frontal and side walls and also the ceiling had metalic anti-spall and anti-vibration layer.

 
All main weapons (AT gun and the HMGs) had sights with 2x zoom (upon the gun there is a drawing of the surroundings). Unfortunately not a single original support for the single HMG was preserved and the plans shall be dug somewhere in the German archives. Therefore these are just approximate replicas. The HMG vz.37 (ZB-53) alone is basically what the Brits know as BESA (rechambered to 0.303). Each single HMG had 2 men crew, the shooter and the loader. 

 
This is one of only three preserved heavy barrels for the HMG vz.37 in Czechia. This barrel would be used exclusively in fortifications. 

 
This is a view into the left gunnery room with an AT gun with coaxial HMG and a twin HMG. Both weapons and supports are original. 

 
Both the HMGs and the AT gun could have been quickly aimed by the body force alone without using elevation and traverse screws (that was also a possibility). The twin HMG vz.37 on the picture had a crew of three (one shooter and two loaders). 

 
I believe the most interesting thing is the AT gun Škoda vz.36. This particular gun was moved to Atlantic Wall in Norway and in 2002 returned back into N-S-82 and moreover with a spare barrel. There are only around ten of such guns preserved worldwide and very few spare barrels (only one or two in Czechia) and these two have matching serial numbers (173 + 2173; 2173 means second barrel for 173) and moreover they originally belonged to this particular bunker!
 
The gun was capable of very rapid fire. Normally 20-30 aimed shots per mimute (depending on the skill of the crew) or up to 40 rounds per minute in autofire mode. That meant that it fired automatically once it was loaded (this was possible max. for 3 minutes and after a water cooling up to 6 minutes long was needed). The shooter could fire both the AT gun and the HMG by the same hand and he could use his second hand and his body to aim like with a gigantic rifle in a ball joint without using traverse and elevation screws. The gun had three loaders - two for the AT gun and one for the HMG. The gun penetration values vary in sources I saw but it shall be around 50 mm of cemented steel at 500 meters and 30°, i.e. more than enough for 1938. Later in the war special ammo with claimed double penetration values was developed by Škoda but I don't know if ever used anywhere.  

 
 
Well, that was N-S-82. Now some more peculiar things from other objects. This is a 15 cm Röchling shell still being stuck in a frontal wall of N-S-91. This object was built in class III therefore the wall on the picture is 2,75 meters thick and if the object was fully completed it would be covered by stones and earth (those would have likely little effect against the Röchling anyway). The wall was not penetrated. Czech fortifications were used for Röchling development just like later also the Belgian ones. However there is an important difference. I believe there is no Röchling hit in the roof in any Czech object while in Belgium the Germans tried the indirect fire and they achieved some very spectacular penetrations. The direct fire used against Czech fortifications was much less effective in terms of penetration but with the indirect fire it was close to impossible to actually hit something. 

 
I believe that this is another Röchling hit in the wall of N-S-49. Maybe a larger calibre for 21 cm guns, honestly I can't recognize. This is an object of an unfinished artilery fortress Skutina and the wall is 3,5 meters thick. It was too high to actually see inside and the object is not accesible from inside for public but it looked like it's not a penetration. Fun fact about this unfinished fortress. The guys who take care of it plan to connect the underground corridor betwen the existing objects where 27 meters were missing by the time when it was abandoned. 

 
Last thing is a replica of .380 ACP SMG vz.38 which was never fielded (on display in the object N-S-84). The SMG was basically developed in one month! It had two magazines, straight for 24 and drum for 96 rounds. 3500 pieces were ordered by the fortification command to be used to protect the entry door or in some light objects which were close to each other in difficult terrain instead of the LMG. The SMG was roughly 4x cheaper than the LMG. Only 15 were made before the order was canceled after Münich. Strangely Czechoslovakia which was very successful in small arms development never fielded an SMG in the interwar period. When the army realised it would be good to actually have one it was too late and moreover it had no money for it (at least the cavalery and artilery wanted it). 
 
Under the SMG You can also see Czechoslovak handgrenades from 1930'. 

 
  
 
 
 
 
 

I like books about tanks so much that I even wrote one myself.
 
https://www.mortonsbooks.co.uk/product/view/productCode/15014
 

good photo showing gap between turret and hull




 
 
"https://www.flickr.com/photos/131561895@N06/27828646347/in/photostream/"
 
 
btw, this APFSDS displayed at WTD91, i think this is 105mm APFSDS for smoothbore(or early design of 120mm DM13, look at fins)
 
i think @SH_MM even posted patent for this APFSDS some time ago

I don't think you're going to get a neat, single answer for all of this.  Penetration is very complicated even when you focus only on rigid OR eroding regimes.   APFSDS occupy a transitional region between those two, meaning it is likely to be even more complex. 
 
For example I did more digging by changing search parameters.  One thing I turned up came from army-guide and this interesting point:
 


 
Completely unsourced but it shows a the potential for multiple factors at work.    I've found sources that allude to nose shape influencing interface defeat, transitions from rigid to eroding penetration and velocity thresholds, and so on.  I'll share the various things I ran across in the hopes it will prove useful.  In no particular order:
 
CTH hydrocode predictions on the effect of rod nose-shape on the velocity at which tungsten alloy rods transition from rigid body to eroding penetrators when impacting thick aluminium targets
 
Abstract:


Design of hard-target penetrator nose geometry in the presence of high-speed, velocity-dependent friction, including the effects of mass loss and blunting
 
Abstract


 
INTERIOR AND TERMINAL BALLISTICS OF 25g LONG ROD PENETRATORS
 
Introduction:



Investigation of Oblique Penetration I: The Effects of Penetrator Leading End Shapes on Unyawed and Yawed Impacts
Abstract



TERMINAL BALLISTICS TEST AND ANALYSIS GUIDELINES FOR THE PENETRATION MECHANICS BRANCH
 
Introduction:


 
Penetration of 6061-T6511 aluminum targets by ogive-nosed VAR 4340 steel projectiles at oblique angles: experiments and simulations
Abstract



The Effect of Nose Shape in Long Rod Penetration
(link to free PDF download)
Abstract:


 
This one seems related to the one below, so I included it more for completion's sake and informative purposes. 
 
Comparative Study of Nose Profile Role in Long-Rod Penetration
Abstract:


 
Honestly I'm not sure this is very relevant.  It seems more about eroding-penetrator processes and mushrooming vs non-mushrooming.  But it's also about EM guns specifically, so it was worth mentioning.
 
Interface Defeat of Long-Rod Projectiles by Ceramic Armor
Abstract:


 
This is mostly about interface defeat in general vs ceramics, but there is a bit in there about nose shape.  So nose shape may be a factor here.
 
Interface defeat studies of long-rod projectile impacting on ceramic targets
 
Abstract:


 
Analysis of the Noneroding Penetration of Tungsten Alloy Long Rods Into Aluminum Targets
Abstract



 
This one seems to be more about rigid penetration, but its also about about LRPs. Worth noting for that 'transitional' aspect I mentioned and the fact nose shape has a huge impact in rigid penetration.
 
Modeling Threshold Velocity of Hemispherical and Ogival-Nose Tungsten-Alloy Penetrators Perforating Finite Aluminum Targets
Abstract

Germany is a bad example for energy emissions because they decided to close all their nuclear plants and decided to take up the slack with...
 
 
Coal and lignite.
 
Can't really go worse emission-wise than those two.

Alright, I forgot about this.
 
I have a whole bunch of stories from the time my dad was in the army, for a reunion they made a little book with all sorts of stories from their time as hussars. I'll try to make a nice story from a bunch of them.
 
Over there in the Netherlands we don't have those massive training areas like they have in the US or Germany, we have to make do with smaller ranges or have areas where we can't fire weapons. The only area where tanks can fire their guns is on a range called "Vliehors", which is on one of our islands. Every once in a while they go there for training, and of course, there has to be a first time for everything. Now, back in those days (1966-67) we had conscription, and conscripts were just assigned a role and had to make do. This did not always turn out well.
 
So, the newly conscripted tankers arrive at the Vliehors for their first life fire shots. They line their Centurions up at the firing range, the commanders give their orders and the Cents point their barrels straight at and old tank used as a target.
 
Except one.
 
When the signal is given, all tanks fire, including the one aiming up. And of course he immediately gets the nicely asked question of "WHAT IN THE FUCK ARE YOU DOING YOU FUCKING MORONS!?".
 
Turns out the gunner heard "Target, brisance, 1800 meters" instead of "Target, armour, 1800 meters", so he aimed like he had an HE shell loaded (and seeing how it's written, he aimed poorly too). So basically he fired an AP shell at angles only used for long range artillery support. They never really figured out where that AP shell went. Probably somewhere in the sea.
 
And that's why we don't have more firing ranges! And it's also why that gunner immediately was a loader after that.
 
 
Anyway, during a later training...
 
My dad, as a fresh Hussar got the task of cleaning the gun of another Centurion. Of course, you can't have a live firing session with a dirty gun, now can you?
He 'happily' went on cleaning the gun, replacing oils, whatever you need to do to clean a tank gun. When he was done the tank was sent on his merry way to the firing range.
Seconds after firing a voice thundered over the range "HUSSAR BRONEEEEEEEEEEEEEEEEEEEEEEEEEEZ!!". To which my dad replied "Sir, I'll immediately get the end-caps of the recoil cylinders and get to cleaning, sir!".
 
I guess you can imagine how the inside of a tank looks when you forget to put the caps back on the recoil system of a tank gun, and fire it.

Alright, I forgot about this.
 
I have a whole bunch of stories from the time my dad was in the army, for a reunion they made a little book with all sorts of stories from their time as hussars. I'll try to make a nice story from a bunch of them.
 
Over there in the Netherlands we don't have those massive training areas like they have in the US or Germany, we have to make do with smaller ranges or have areas where we can't fire weapons. The only area where tanks can fire their guns is on a range called "Vliehors", which is on one of our islands. Every once in a while they go there for training, and of course, there has to be a first time for everything. Now, back in those days (1966-67) we had conscription, and conscripts were just assigned a role and had to make do. This did not always turn out well.
 
So, the newly conscripted tankers arrive at the Vliehors for their first life fire shots. They line their Centurions up at the firing range, the commanders give their orders and the Cents point their barrels straight at and old tank used as a target.
 
Except one.
 
When the signal is given, all tanks fire, including the one aiming up. And of course he immediately gets the nicely asked question of "WHAT IN THE FUCK ARE YOU DOING YOU FUCKING MORONS!?".
 
Turns out the gunner heard "Target, brisance, 1800 meters" instead of "Target, armour, 1800 meters", so he aimed like he had an HE shell loaded (and seeing how it's written, he aimed poorly too). So basically he fired an AP shell at angles only used for long range artillery support. They never really figured out where that AP shell went. Probably somewhere in the sea.
 
And that's why we don't have more firing ranges! And it's also why that gunner immediately was a loader after that.
 
 
Anyway, during a later training...
 
My dad, as a fresh Hussar got the task of cleaning the gun of another Centurion. Of course, you can't have a live firing session with a dirty gun, now can you?
He 'happily' went on cleaning the gun, replacing oils, whatever you need to do to clean a tank gun. When he was done the tank was sent on his merry way to the firing range.
Seconds after firing a voice thundered over the range "HUSSAR BRONEEEEEEEEEEEEEEEEEEEEEEEEEEZ!!". To which my dad replied "Sir, I'll immediately get the end-caps of the recoil cylinders and get to cleaning, sir!".
 
I guess you can imagine how the inside of a tank looks when you forget to put the caps back on the recoil system of a tank gun, and fire it.

Explosive ordnance types found in Afghanistan: https://jmu.edu/cisr/research/OIG/Afghanistan/high res/
Explosive ordnance types found in Iraq: https://jmu.edu/cisr/research/OIG/Iraq/highres/

Zumwalt's AGS gun mounting overview

 
Magazine overview

 
 

@N-L-M@Collimatrix
 

 
Presentation about big caliber guided shells from an AC-130. This isn't the complete presentation but I wasn't going to screencap and upload 52 sheets. This is most of the interesting stuff anyway.

Compared to the most well known Japanese fighter of World War 2, the A6M “Zero”, the J2M Raiden (“Jack”) was both less famous and less numerous. More than 10,000 A6Ms were built, but barely more than 600 J2Ms were built. Still, the J2M is a noteworthy aircraft. Despite being operated by the Imperial Japanese Navy (IJN), it was a strictly land-based aircraft. The Zero was designed with a lightweight structure, to give extreme range and maneuverability. While it had a comparatively large fuel tank, it was lightly armed, and had virtually no armor. While the J2M was also very lightly built, it was designed that way to meet a completely different set of requirements; those of a short-range interceptor. The J2M's design led to it being one of the fastest climbing piston-engine aircraft in World War 2, even though its four 20mm cannons made it much more heavily armed than most Japanese planes.
 
 

 
Development of the J2M began in October 1938, under the direction of Jiro Hirokoshi, in response to the issuance of the 14-shi interceptor requirement (1). Hirokoshi had also designed the A6M, which first flew in April 1939. However, development was slow, and the J2M would not make its first flight until 20 March 1942, nearly 3 ½ years later (2). Initially, this was due to Mitsubishi's focus on the A6M, which was further along in development, and of vital importance to the IJN's carrier force. Additionally, the J2M was designed to use a more powerful engine than other Japanese fighters. The first aircraft, designated J2M1, was powered by an MK4C Kasei 13 radial engine, producing 1430 horsepower from 14 cylinders (3) (compare to 940 horsepower for the A6M2) and driving a three bladed propeller. The use of such a powerful engine was driven by the need for a high climb rate, in order to fulfill the requirements set forth in the 14-shi specification.
 
The climb rate of an aircraft is driven by specific excess power; by climbing an aircraft is gaining potential energy, which requires power to generate. Specific Excess Power is given by the following equation;
 
(Airspeed*(Thrust-Drag))/Weight
 
 
 
It is clear from this equation that weight and drag must be minimized, while thrust and airspeed are maximized. The J2M was designed using the most powerful engine then available, to maximize thrust. Moreover, the engine was fitted with a long cowling, with the propeller on an extension shaft, also to minimize drag. In a more radical departure from traditional Japanese fighter design (as exemplified by aircraft such as the A6M and Ki-43), the J2M had comparatively short, stubby wings, only 10.8 m wide on the J2M3 variant, with a relatively high wing loading of 1.59 kN/m2 (33.29 lb/ft2) (2). (It should be noted that this wing loading is still lower than contemporary American aircraft such as the F6F Hellcat. The small wings reduced drag, and also reduced weight. More weight was saved by limiting the J2M's internal fuel, the J2M3 had only 550 liters of internal fuel (2).
 
Hirokoshi did add some weight back into the J2M's design. 8 millimeters of steel armor plate protected the pilot, a luxurious amount of protection compared to the Zero. And while the J2M1 was armed with the same armament as the A6M (two 7.7mm machine guns and two Type 99 Model 2 20mm cannons), later variants would be more heavily armed, with the 7.7mm machine guns deleted in favor of an additional pair of 20mm cannons. Doubtlessly, this was driven by Japanese wartime experience; 7.7mm rounds were insufficient to deal with strongly built Grumman fighters, let alone a target like the B-17.
 
The first flight of the J2M Raiden was on March 20th, 1942. Immediately, several issues were identified. One design flaw pointed out quickly was that the cockpit design on the J2M1, coupled with the long cowling, severely restricted visibility. (This issue had been identified by an IJN pilot viewing a mockup of the J2M back in December 1940 (1).) The landing speed was also criticized for being too high; while the poor visibility over the nose exacerbated this issue, pilots transitioning from the Zero would be expected to criticize the handling of a stubby interceptor.
 

Wrecked J2M in the Philippines in 1945. The cooling fan is highly visible.
 
However, the biggest flaw the J2M1 had was poor reliability. The MK4C engine was not delivering the expected performance, and the propeller pitch control was unreliable, failing multiple times. (1) As a result, the J2M1 failed to meet the performance set forth in the 14-shi specification, achieving a top speed of only 577 kph, well short of the 600 kph required. Naturally, the climb rate suffered as well. Only a few J2M1s were built.
 
The next version, the J2M2, had several improvements. The engine was updated to the MK4R-A (3); this engine featured a methanol injection system, enabling it to produce up to 1,800 horsepower for short periods. The propeller was switched for a four blade unit. The extension shaft in the J2M1 had proved unreliable, in the J2M2 the cowling was shortened slightly, and a cooling fan was fitted at the the front. These modifications made the MK4R-A more reliable than the previous engine, despite the increase in power.
 
However, there were still problems; significant vibrations occurred at certain altitudes and speeds; stiffening the engine mounts and propeller blades reduced these issues, but they were never fully solved (1). Another significant design flaw was identified in the summer of 1943; the shock absorber on the tail wheel could jam the elevator controls when the tailwheel retracted, making the aircraft virtually uncontrollable. This design flaw led to the death of one IJN pilot, and nearly killed two more (1). Ultimately, the IJN would not put the J2M2 into service until December 1943, 21 months after the first flight of the J2M1. 155 J2M2s would be built by Mitsubishi (3).
 
By the time the J2M2 was entering service, the J2M3 was well into testing. The J2M3 was the most common variant of the Raiden, 260 were produced at Mitsubishi's factories (3). It was also the first variant to feature an armament of four 20mm cannons (oddly, of two different types of cannon with significantly different ballistics (2); the 7.7mm machine guns were replace with two Type 99 Model 1 cannons). Naturally, the performance of the J2M3 suffered slightly with the heavier armament, but it still retained its excellent rate of climb. The Raiden's excellent rate of climb was what kept it from being cancelled as higher performance aircraft like the N1K1-J Shiden came into service.
 

 
The J2M's was designed to achieve a high climb rate, necessary for its intended role as an interceptor. The designers were successful; the J2M3, even with four 20mm cannons, was capable of climbing at 4650 feet per minute (1420 feet per minute) (2). Many fighters of World War 2, such as the CW-21, were claimed to be capable of climbing 'a mile a minute', but the Raiden was one of the few piston-engine aircraft that came close to achieving that mark. In fact, the Raiden climbed nearly as fast as the F8F Bearcat, despite being nearly three years older. Additionally, the J2M could continue to climb at high speeds for long periods; the J2M2 needed roughly 10 minutes to reach 30000 feet (9100 meters) (4), and on emergency power (using the methanol injection system), could maintain a climb rate in excess of 3000 feet per minute up to about 20000 feet (about 6000 meters).
 
 
 
 
 

 
 
 
 
 

 
Analysis in Source (2) shows that the J2M3 was superior in several ways to one of its most common opponents, the F6F Hellcat. Though the Hellcat was faster at lower altitudes, the Raiden was equal at 6000 meters (about 20000 feet), and above that rapidly gained superiority. Additionally, the Raiden, despite not being designed for maneuverability, still had a lower stall speed than the Hellcat, and could turn tighter. The J2M3 actually had a lower wing loading than the American plane, and had flaps that could be used in combat to expand the wing area at will. As shown in the (poorly scanned) graphs on page 39 of (2), the J2M possessed a superior instantaneous turn capability to the F6F at all speeds. However, at high speeds the sustained turn capability of the American plane was superior (page 41 of (2)).
 
The main area the American plane had the advantage was at high speeds and low altitudes; with the more powerful R-2800, the F6F could more easily overcome drag than the J2M. The F6F, as well as most other American planes, were also more solidly built than the J2M. The J2M also remained plagued by reliability issues throughout its service life.
 
In addition to the J2M2 and J2M3 which made up the majority of Raidens built, there were a few other variants. The J2M4 was fitted with a turbo-supercharger, allowing its engine to produce significantly more power at high altitudes (1). However, this arrangement was highly unreliable, and let to only two J2M4s being built. Some sources also report that the J2M4 had two obliquely firing 20mm Type 99 Model 2 cannons in the fuselage behind the pilot (3). The J2M5 used a three stage mechanical supercharger, which proved more reliable than the turbo-supercharger, and still gave significant performance increases at altitude. Production of the J2M5 began at Koza 21st Naval Air Depot in late 1944 (6), but ultimately only about 34 would be built (3). The J2M6 was developed before the J2M4 and J2M6, it had minor updates such as an improved bubble canopy, only one was built (3). Finally, there was the J2M7, which was planned to use the same engine as the J2M5, with the improvements of the J2M6 incorporated. Few, if any, of this variant were built (3).
 
A total of 621 J2Ms were built, mostly by Mitsubishi, which produced 473 airframes (5). However, 128 aircraft (about 1/5th of total production), were built at the Koza 21st Naval Air Depot (6). In addition to the reliability issues which delayed the introduction of the J2M, production was also hindered by American bombing, especially in 1945. For example, Appendix G of (5) shows that 270 J2Ms were ordered in 1945, but only 116 were produced in reality. (Unfortunately, sources (5) and (6) do not distinguish between different variants in their production figures.)
 
Though the J2M2 variant first flew in October 1942, initial production of the Raiden was very slow. In the whole of 1942, only 13 airframes were produced (5). This included the three J2M1 prototypes. 90 airframes were produced in 1943, a significant increase over the year before, but still far less than had been ordered (5), and negligible compared to the production of American types. Production was highest in the spring and summer of 1944 (5), before falling off in late 1944 and 1945.
 
The initial J2M1 and J2M2 variants were armed with a pair of Type 97 7.7mm machine guns, and two Type 99 Model 2 20mm cannons. The Type 97 used a 7.7x56mm rimmed cartridge; a clone of the .303 British round (7). This was the same machine gun used on other IJN fighters such as the A5M and A6M. The Type 99 Model 2 20mm cannon was a clone of the Swiss Oerlikon FF L (7), and used a 20x101mm cartridge.
 
The J2M3 and further variants replaced the Type 97 machine guns with a pair of Type 99 Model 1 20mm cannons. These cannons, derived from the Oerlikon FF, used a 20x72mm cartridge (7), firing a round with roughly the same weight as the one used in the Model 2 at much lower velocity (2000 feet per second vs. 2500 feet per second (3), some sources (7) report an even lower velocity for the Type 99). The advantage the Model 1 had was lightness; it weighed only 26 kilograms vs. 34 kilograms for the model 2. Personally, I am doubtful that saving 16 kilograms was worth the difficulty of trying to use two weapons with different ballistics at the same time. Some variants (J2M3a, J2M5a) had four Model 2 20mm cannons (3), but they seem to be in the minority.
 

 
 
In addition to autocannons and machine guns, the J2M was also fitted with two hardpoints which small bombs or rockets could be attached to (3) (4). Given the Raiden's role as an interceptor, and the small capacity of the hardpoints (roughly 60 kilograms) (3), it is highly unlikely that the J2M was ever substantially used as a bomber. Instead, it is more likely that the hardpoints on the J2M were used as mounting points for large air to air rockets, to be used to break up bomber formations, or ensure the destruction of a large aircraft like the B-29 in one hit. The most likely candidate for the J2M's rocket armament was the Type 3 No. 6 Mark 27 Bomb (Rocket) Model 1. Weighing 145 pounds (65.8 kilograms) (8), the Mark 27 was filled with payload of 5.5 pounds of incendiary fragments; upon launch it would accelerate to high subsonic speeds, before detonating after a set time (8). It is also possible that the similar Type 3 No. 1 Mark 28 could have been used; this was similar to the Mark 27, but much smaller, with a total weight of only 19.8 pounds (9 kilograms).
 
 
 
The first unit to use the J2M in combat was the 381st Kokutai (1). Forming in October 1943, the unit at first operated Zeros, though gradually it filled with J2M2s through 1944. Even at this point, there were still problems with the Raiden's reliability. On January 30th, a Japanese pilot died when his J2M simply disintegrated during a training flight. By March 1944, the unit had been dispatched to Balikpapan, in Borneo, to defend the vital oil fields and refineries there. But due to the issues with the J2M, it used only Zeros. The first Raidens did not arrive until September 1944 (1). Reportedly, it made its debut on September 30th, when a mixed group of J2Ms and A6Ms intercepted a formation of B-24s attacking the Balikpapan refineries. The J2Ms did well for a few days, until escorting P-47s and P-38s arrived. Some 381st Raidens were also used in defense of Manila, in the Phillipines, as the Americans retook the islands. (9) By 1945, all units were ordered to return to Japan to defend against B-29s and the coming invasion. The 381st's J2Ms never made it to Japan; some ended up in Singapore, where they were found by the British (1).
 

 
 
least three units operated the J2M in defense of the home islands of Japan; the 302nd, 332nd, and 352nd Kokutai. The 302nd's attempted combat debut came on November 1st, 1944, when a lone F-13 (reconaissance B-29) overflew Tokyo (1). The J2Ms, along with some Zeros and other fighters, did not manage to intercept the high flying bomber. The first successful attack against the B-29s came on December 3rd, when the 302nd shot down three B-29s. Later that month the 332nd first engaged B-29s attacking the Mitsubishi plant on December 22nd, shooting down one. (1)
The 352nd operated in Western Japan, against B-29s flying out of China in late 1944 and early 1945. At first, despite severe maintenace issues, they achieved some successes, such as on November 21st, when a formation of B-29s flying at 25,000 feet was intercepted. Three B-29s were shot down, and more damaged.

In general, when the Raidens were able to get to high altitude and attack the B-29s from above, they were relatively successful. This was particularly true when the J2Ms were assigned to intercept B-29 raids over Kyushu, which were flown at altitudes as low as 16,000 feet (1). The J2M also had virtually no capability to intercept aircraft at night, which made them essentially useless against LeMay's incendiary raids on Japanese cities. Finally the arrival of P-51s in April 1945 put the Raidens at a severe disadvantage; the P-51 was equal to or superior to the J2M in almost all respects, and by 1945 the Americans had much better trained pilots and better maintained machines. The last combat usage of the Raiden was on the morning of August 15th. The 302nd's Raidens and several Zeros engaged several Hellcats from VF-88 engaged in strafing runs. Reportedly four Hellcats were shot down, for the loss of two Raidens and at least one Zero(1). Japan surrendered only hours later.

At least five J2Ms survived the war, though only one intact Raiden exists today. Two of the J2Ms were captured near Manila on February 20th, 1945 (9) (10). One of them was used for testing; but only briefly. On its second flight in American hands, an oil line in the engine failed, forcing it to land. The aircraft was later destroyed in a ground collision with a B-25 (9). Two more were found by the British in Singapore (1), and were flown in early 1946 but ex-IJN personnel (under close British supervision). The last Raiden was captured in Japan in 1945, and transported to the US. At some point, it ended up in a park in Los Angeles, before being restored to static display at the Planes of Fame museum in California.
 
 

 
 
Sources:
 
 
https://www.docdroid.net/gDMQra3/raiden-aeroplane-february-2016.pdf#page=2
F6F-5 vs. J2M3 Comparison
http://www.combinedfleet.com/ijna/j2m.htm
http://www.wwiiaircraftperformance.org/japan/Jack-11-105A.pdf
https://babel.hathitrust.org/cgi/pt?id=mdp.39015080324281;view=1up;seq=80
https://archive.org/stream/corporationrepor34unit#page/n15/mode/2up
http://users.telenet.be/Emmanuel.Gustin/fgun/fgun-pe.html
http://ww2data.blogspot.com/2016/04/imperial-japanese-navy-explosives-bombs.html
https://www.pacificwrecks.com/aircraft/j2m/3008.html
https://www.pacificwrecks.com/aircraft/j2m/3013.html
https://www.pacificwrecks.com/aircraft/j2m/3014.html
 
 
Further reading:
 
An additional two dozen Raiden photos: https://www.worldwarphotos.info/gallery/japan/aircrafts/j2m-raiden/
 
 

For the mean time:
 
 
Updated Special Armor Locations:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fuel Tank Locations:
 
 
 
 
 
 
 
 
Main Gun Ammunition Locations:
 
 
 
 
 
 
 
Crew Locations:
 
 
 
 
 
 
Armament Locations:
 
 
 
 
 
Powerpack Location:
 
 
 
 
 
 

Here is a diagram with the crew (blue) and special armor volumes (red) highlighted. Spaced armor (i.e. mantlet, heavy side skirts, right front hull, etc.) is not highlighted: