Bronezhilet

Calliope on a budget.
 

Interesting choice really. You seldom see photos of them that weren't either taken in Korea or on the roof of a gas station in LA.

*cracks fingers*

Something that has interested me for a while, are shape stabilised projectiles. As in, projectiles that are stable due to their shape. Everybody has heard of rotation stabilised and fin stabilised projectiles, but shape stabilised is kind of different. I guess most of you here have seen shape stabilised projectiles without actually knowing how and why they work.

Geek sidenote: Fin stabilised projectiles are actually fin and rotation stabilised.

As I said, shape stabilised projectile have a stable flight path due to their unique shape.

Figure 1: A 84mm Carl Gustav shape stabilised HEAT-round

Note the slightly ogive front and the stand-off, which are characteristic of shape stabilised projectiles (SSP). Both features are absolutely crucial for the SSP to work.
I'm going to throw you guys into the deep end by showing a .gif of the airflow in front of an SSP.
Here's a link because I can't embed .gifv apparently
The first thing you should notice is the air circulating in some-sort of pocket, and that this airflow is subsonic. Before I continue, here's the airflow in front of a blunt projectile: Clicketyclick
While that projectile has a subsonic airflow in front of it as well, it is not circulating.

Here's the airspeed of both projectiles as a normal picture:

Figure 2: Airspeed in front of an SSP


Figure 3: Airspeed in front of a blunt projectile

It's clear that an SSP has a ogive-shaped subsonic airpocket in front of the projectile. This basically emulates the ogive of a normal rotation stabilised projectile. In other words, it makes it more aerodynamic. But does that airpocket stabilise the projectile?
No it does not.

So why is this projectile stabilised? The key is in what happens when it starts to tumble. Right now, there is nothing stopping the projectile from tumbling, and that's the interesting thing. There is literally nothing stopping the projectile from tumbling, except...


the projectile itself.

Lets take a look at what happens when an SSP starts to tumble. (If I remember correctly, I rotated the projectile 10 degrees)
First off, the airflow in front of the projectile. It's fairly obvious that the airflow has changed. Lets check that again, but this time as a picture.

Figure 4: Airflow in front of a tumbling SSP

Again, it's obvious that the airflow has changed. The subsonic pocket has mainly shifted to one side and the air itself isn't really circulating in the pocket. This change causes a huge change in the Cd of the projectile. Let me show you why.

Figure 5: Pressure in front of a tumbling SSP

Next, the pressure in front of an SSP flying straight.

Figure 6: Pressure in front of an SSP flying straight

Please note the approximate pressure in front of both projectiles. The tumbling projectile has, on one side, twice the pressure as the projectile that's flying straight. Very interesting. What's even more interesting is that the pressure occurs on the opposite of the side it's turning to! The projectile is turning upwards, but the pressure builds up at the bottom. This pressure forces the projectile to start turning down again, forcing the projectile in a state where the pressure on all sides is equal.

Voila, a shape stabilised projectile.


But... why does it work?

The subsonic airpocket is created by the stand-off and that little flange, or whatever you want to call it. The dimensions and placement of both are equally important. The stand-off and its side create the airpocket and the flange give the airpocket the required shape. The stand-off size can vary, but the flange size and placement is very important. If the flange is too far forward or too far back, the airpocket will be either too small or too big. Why does the size of the pocket matter? Because of this:

Figure 7: Subsonic pocket in front of an SSP

I changed the parameters slightly and made all airflow above Mach 1 red. Whatever is not red, is trans- or subsonic. The interesting thing to note here, is the pocket extends to the edge of the projectile (if I made the projectile better it should be exactly on the edge). (Sidenote: Here's the same picture of an SSP at a 10° angle)
While the airpocket does not start at the flange, the flange determines where the pocket starts. If, at this velocity, the flange was further back, there would be supersonic flow hitting the front of the projectile, massively increasing drag. If the flange was further forward, the airpocket would be further forward too. This would mean the airpocket would not end at the edge of the projectile, but further out. Creating an airpocket which is wider than the projectile. This would allow the projectile to tumble a bit, because pressures wouldn't change much unless there is supersonic flow hitting the projectile.

It is also possible to change the size of the airpocket by changing the front of the projectile itself. If the radius connecting the front and the stand-off is too big, the airflow inside the pocket would disrupt the circulation. The same would happen if the radius is too small. The angle of the front is important as well, but I haven't expermented that much with it so I don't know how important it exactly is, but it has an effect on the airflow.

By the way, if the flange did not exist at all, the airpocket would start at around a third to half of the stand-off. Which would completely ruin the airpocket. Without a flange, the stand-off itself would have to be way bigger and longer to create the same kind of airpocket.

But Bronezhilet, I hear you cry, if the airspeed changes, the pocket changes as well!

I'm glad you brought that up, because you are right.

A shape stabilised projectile only works properly within a certain flight envelope. If the projectile is moving too fast, the airpocket would compress allowing supersonic flow to hit the front of the projectile. Which in turns increases drag. By a lot. If the projectile is moving too slow the airpocket widens, allowing the projectile to tumble a bit before it would stabilise.

I've been brainstorming with Colli a bit, and we've come to the conclusion that is why some projectiles are both shape stabilised and fin stabilised. When the projectile is moving too slow for shape stabilisation, the fins would keep it pointing in the right direction.



And that concludes today's lesson. Thank you for reading.

Rebuttal 2: The Rebuttening goes up next Tuesday, but yeah I'll repost it after that.

My sturm was picked up off of a dead kraut on the Western Front according to the widow of the old dude who sold it.
 
I also was at our local high end gun store one day (that always has a sturm or two) and an older guy and his ancient father came in. The father pointed to the sturm, muttered something, and his son said "hey, my dad says he was issued one of those". The store froze and my ears perked up to hear what was going on. The old man spoke very bad English but they gave him the rifle to hold and he knew the controls by heart and his son was translating things like how many magazines he was issued, where he kept them on his person, and that they were ordered to never use full auto. If I recall correctly his son said he was 17 when he fought.
 
It was eerie to see, but it was the only time I have ever seen a German WWII vet talk about their experience in person.

It's akin to "who had the best pistol of WW2".. The proper answer is "Does it matter?".

Ian and Karl are putting far too much stock in a weapon that offered a small firepower advantage in a war where 80% of causalities were caused by artillery and aerial bombardment.

Oh deer.

Pfff.  I don't believe that Putin has the stones to nuke California.  I dare him to.  He can go right ahead and try.

alright heres my official write-up, im drunk on cheeseburgers and liquor so excuse the spelling
 
1. "Mp-44 was fielded in large enough numbers to change combat doctrine"
 
- in what way other than having sub-machine gun armed troops having more accurate fire did it change jack. Now ian and fuckface are coming at this from a tatical standpoint, and i would agree that a German infantry squad quibbled with stg-44s does have a noticably large increase in volume of fire.
 
But the problem is that infantry on the modern battlefield are so fucking unimaginably fragile that unless millions of said infantrymen have this amount of volume of fire increased, its not going to change shit
Unlike the Americans who could issue the M1-garand in the millions, and the Russians who could issue far larger numbers of sub-machine guns than the Germans
 
You just have to think of this in strategic terms, not tactical
 
Lets say your assaulting a town, you infantry have to attack from outside of a forest about say 600 meters away from the first lines of defense for the town. How many of those infantrymen are going to be dieing from machine-gun fire alone
How many from rifle fire?
 
How many from any support assets (tanks, mortars, planes) 
 
How many infantrymen will fall before they even get a chance open fire at their enemies at any range where it matters
 
Infantry are useful when it comes to creating and occupying territory
 
A joke among me and my friends is that "Infantry create the lines, everything else is made to break them"
 
So when you get into ranges that it matters, if you exclude all other factors, the side with the greater volume of fire usually wins out
 
Think of it like this
 
Its a AH civil war battle, where one side, is predominately fielding muskets, with some level action repeating rifles spread in-between them here and there
 
And the other side is fielding bolt action rifles
Fact is, the side that is stacked full of soldiers with more rifles that can fire faster is usually going to beat the side with a few rifles that can fire extremely fast mixed in with a bunch of sluggers
 
But non of this matters if one side has such an advantage in artillery, positioning, tanks, machine guns or any other factors that chew infrantry up much, much faster than rifle rounds
 
So unless every other grunt who would be stuck with a Mauser gets his hands on a STG, its not going to matter. Because chances are the bloke with the STG is going to die to shrapnel or machine gun fire or the fact that the rest of his squad is still armed with mausers that just cant put out a large enough volume of fire
 
And even if every nazi under the sun had an stg, its still not going to guarantee them jack 
 
Look at Korea, where the US army learned the hard way that having lots of submachine guns is really useful, and having every rifleman trying to be some type sharpshooter isnt
 
The chinese still toke many, many more casualties. They had less artillery, less tanks, less aircraft and they never could compensate
 
It dosent matter if your high volume of fire ambush whips out a whole platoon, if the other guy can call artillery down to wipe out 5 platoons of your own, and you cant do jack
 
2. he said it was situational, which its is 
 
Though im a proud member of the full auto master race, thats with shooting groups of soda cans with 5.45, the round the STG-44 fires kicks up a hell of a lot more recoil. 
So the idea that your going to be doing anything but suppressible fire and door kicking with this is crazy
 
3. the 5 guys with garands vs 1 guy with an STG
 
Thats just not how wars are fought son, i dont know who told you otherwise
 
they are fought by the 3,000 guys with garands versus the 60 odd guys with STGs, and the rest with Kar-98s (this is excluding machine guns and submachine guns)
 
 
and since both sides are going to be losing alot of those guys before they infrantry even get in small arms range, i rather be on the side of the freedom 
 
And sure, i would choose the Stg over the Garand in a heartbeat
 
I would also choose the Panther over the Sherman
 
But this is for a 1v1 fantast fight
 
in real wars, you have other people behind you
 
and the side that wins is the side with the 10 or so garands for every STG and the side of 20 or so Shermans for every panther
 
and since i dont like the idea of surrending, sign me up for the m1 
 
4. "if you look at any other assualt rifle afterwords"
 
ah yes
 
The old "the Germans invented everything because post war arms look like them" line
 
Well there fuckface, i assume you would agree with the fact the germans invented the main battle tank
Because like the panther, future MBTs have slopped armor and torision bar suspension
 
But the fact is, much, much more goes into design than that
 
Just like though an AK looks like an STG, its the parts inside of it that count
 
5. "Russians cant stamp anything"
 
 
go fuck yourself
 
 
6. "Russians only use human wave attacks"
 
Its at this point i was embarrassed to learn i had missed the ten gallon hick hat fuckface was wearing, and i was still attempting to be objective with this video 
 
7. Would be useful today   Expect you would have the recoil of the commie with the AKM but you lack the realibality, you have the fragility of the guy with the m16 but lack the accuracy, and you lack the accuracy, recoil control, and satan approved wound profile of the commie with the AK-74   oh ya, totally close 

Lets just say ian and fuckface mcweridbeard are damn lucky they live in a different country than i do, or else i would be making some very drunk, very angry call ins during their show 

Ukrainian self-propelled armored bank office for use in Donetsk and Luhansk regions.

 

 

 

 

Assault rifle is a very arbitrary term. Were it not for the fact that it is a handy way to describe a bunch of semi-automatic rifles with detachable magazines, I'd say get rid of the term.
 
Also, the fact that the "intermediate cartridge" is the defining characteristic is also hilarious.

Did they really say that its the first true assault rifle because Hitler himself said so, or did I misunderstand?
 
If I understood correctly: That's bullshit logic. Hitler approved the mass production of the 188-ton Maus tank. I'm not sure what the opinion of a batshit insane dude has to do with this.

Nathaniel, thou hath been called out:
 
https://www.full30.com/video/e6d39490c7cbaf8a20a80fcdbc9f1c86

Simo's influence on the course of the war wasn't that big anyway. Implying Finland lost their territory and assets because a certain sniper used the 'wrong' caliber bullet is retarded.

100,000 rounds of .22 LR isn't prepping, It's an investment son!
 
Just you wait until it's always out of stock and hard to find in gun stores again and then see who's laughing!

Those are photos of the Dutch Army testing both the Leo 1 and Chieftain to determine the successor to the Centurion. These photos are from around 1968.
DBV means "Detachement Beproeving Voertuigen", which translates to "Detachment for testing of vehicles".

Time to make y'all jelly.
 

Less than 2 km away from base. Highlighted city is about 50% under control of SAA. Assault is conducted by Sukheil Khasan's brigade. 

Only one "system" with two methods of actuation on the Kitty. The electrical firing is just a solenoid that trips the mechanical release.
 
The vast majority of civvy arty loads are homerolled. If you're lucky you have some original cases, some projos that are sound, and from there it's "Figure it out".
In the case of the 76, most are taking the far more common 3" naval projos and turning down the obturator rings (The 3" runs at a higher pressure than the '76, even though the nominal shot size is the same.).
 
The projos are usually "set" in the case (You'll see masking tape used sometimes) and not solidly crimped (improves case life) which can cause a mess when dealing with a misfire or fouling . Seen more than a few times where the projo pulls out and you're left with a spill of propellant as the case is drawn out.  Then the cleaning rods come out and the projo is persuaded to back out the tube.
 
Priming can vary. A lot. Considering the number of misfires I've seen with original, supposedly "sound" arty primers, versus often homerolled primers I'm not going to guess as to what was used.
 
Propellant can be variable, and here is where I think there was an issue.  The stuff can absorb moisture which will change it's behavior to an extent. How it's stored will also cause issues. Too much heat will "cook" the volatiles from it (when you open a can of surplus ammo and get that sweet-ish nitro smell for example) and change it's burn rate and sensitivity.  So a weak primer plus a load of surplus propellant that was not well stored at some time in it's life, and you have potential problems.
 
Lastly is an issue with surplus armor in general, and that is most of it is old, and parts, especially for the noisy bits are incredibly scarce (By design).  We have no idea what state the lockwork was in and how sound or unsound it may have been.   We also do not know how well treated or mistreated they were in previous use, and these things saw LOADS of previous use (or abuse) . 
Unless you're very very wealthy and have scads of free time, you're having to rediscover everything about your chosen piece from scratch, as there is shockingly little hard info out there about them ( Also "By design"), and you're having to do this when you can, as you can.
 
All of which leads to the potential for accidents like we had recently. Any one of a number of potential things could have caused it, and eventually you can get so wrapped up in the safety that you're afraid to shoot the silly thing.  (kind of defeating the purpose of owing a live eargesplittenloudenboomer.)
 
It's definitely a hobby that has the potential to get messy. 
I'm just hoping some shitbird bureaucrat does not use this as an excuse to close the registry on DD's, because compared to some hobbies, it has a fantastic safety record considering the energies and potential for "oh shits" you're dealing with.

It looks like they are indeed some form of shape stabilisation. But I have my doubts on how effective the stabilisation actually is.
 
 
Yes, but then your accuracy goes to shit.
 
You cannot rotation stabilise flechettes. If you do try, your shot pattern at a few meters will look like this:

Not every effective at longer ranges.
 
So you're stuck with a more elegant version of your every day shot.

It looks like they are indeed some form of shape stabilisation. But I have my doubts on how effective the stabilisation actually is.
 
 
Yes, but then your accuracy goes to shit.
 
You cannot rotation stabilise flechettes. If you do try, your shot pattern at a few meters will look like this:

Not every effective at longer ranges.
 
So you're stuck with a more elegant version of your every day shot.

Time to make y'all jelly.
 

Well dont worry, Cancer has a much lower morality rate than German Tiger crews during world war 2