Collimatrix

The side turret armor of the K2 has always thrown me for a loop. Maybe there's more than meets the eye but it's hard to say. 
 
Regardless here's a picture from one of the discussions on the Korean side of the internet on the protection of the side turret wall
 
And the unwatermarked slides that SH_MM posted
 

Not sure if this has been posted here before, if so, forgive me.
 
https://patents.google.com/patent/US6662726B1/en?oq=US+6%2c662%2c726+B1
 
This is a patent by General Dynamics Ordnance and Tactical Systems Inc for a kinetic energy penetrator. 
 
The initial filing date is 03/08/2000 and the patent was publicized 12/16/2003, which matches up very closely with the M829A3 program. I believe this patent shows the design behind M829A3, feel free to read through and draw you own conclusions. 
 
Things I noted:
The round is shown defeating what appears to be dual-flyer plate ERA It is said to have a tungsten tip and DU main rod, as opposed to the conventional idea that the tip is steel  

Depending on exactly what grade of steel it is, it may be weldable, or at the very least it could be riveted and used to carry loads.  Even extremely high hardness steel is a much better structural material than any ceramic, which is purely dead weight from a structural standpoint.

Rolled metal laminates are less limited in thickness than explosively bonded ones.  On the other hand, explosive bonding (at least if you do it right) has a stronger bond between the layers, and allows the bonding of highly dissimilar metals (like steel and aluminum).

One thing that the designer must be very careful with when making double or triple hardness steel laminates is that the different sorts of steel laminated together have the same martensite start temperature even if they do not have the same final hardness.  The martensitic phase transformation has a small, but extremely rapid volume change (and actually this is why katanas are curved back like that; when the edge transforms into martensite it actually gets slightly more voluminous and bends the entire blade backwards).  If the two plates don't transform simultaneously they can shear apart.

The AS21 is by no means based on the K21. It’s a completely new platform. 

Triple hardness steel and dual hardness steel is created by rolling multiple steel plates with different properties together in multiple stages.
 

This requires more stages of rolling (IIRC triple hardness steel requires four), hence it takes much more time to make.
 

Hi,
Just a head's up of a new book just published by the Tank Museum at Bovington. It is Richard Ogorkiewicz's autobiography which he had just completed before his death and which was brought to publication thorough the determination of David Willey, Curator of the museum. I received the book out of the blue  as a gift, through I think, the good offices of 
Richard's wife. The book is entitled "Observer of Cold War tank development", it is 78 pages long and richly illustrated and is full of interesting facts and personal anecdotes. 
Once available for general sale, it looks likes it will be a purchase well made.
Cheers
Marsh

Baryshev's day on Sofa experts.
 

 

 
 

 
 
   Upper picture - during a moment of shot, second - case extraction
 
 
 

 
 
 
 

 
 

 

 
 
 
 

 

 
 

Lift jet installation in the YAK-38

The AMX-40 was the first French MBT to feature NERA (a.k.a PAC in French ; shock-accelerated plates) :
 

 

During report of news channel people managed to spot radio-blocking device in airintake of an SU-57.

 
   Airintake

 
   Test model:
 

Photo of loitering munition, used by SAA in Southern Idlib (Ariha).

 
   Video of strike
https://radikal.ru/video/YUxWC3HcOQO
 
   Earlier this year:

   Possible Iranian made and fieldtested in Syria, or Syrian made using Iranian parts loitering munition.

Hopefully this has not been posted already:


 

Yeah, I think I see a problem.
 
The return spring for the bolt carrier has to be stronger than the bolt spring, or the bolt carrier cannot force the bolt into battery.  The return spring is exerting the least force when the bolt carrier is near battery, because that's how springs work (Hooke's Law, yo).  So there's a very fine balance between having the bolt spring be strong enough to do anything but having the bolt carrier return spring still be able to perform its job.


Needless to say, this is not a good way to do things.

GMerlon is correct but if you happen to experience a soft head failure the entire rifle is probably going to be wrecked and you are heading to the ER or undertaker.

 
Example of a soft head failure I investigated.  This happened on the sixth round in a M1 Garand.  I was contacted and told him to send me all the fired cases prior to it and he did.  Headspace was perfect on the first 5 and no 6 completely wrecked the Garand.
 
This round was loaded in Britain for the Greek Army in the 50s and found out this arsenal had these prior.  The bolt lugs held, the receiver held but the escaping gas broke the lower stock in about 5 pieces.
 
Soft heads occur when the cases go through the annealing line upside down and the flames are directed at the head of the case instead of the neck/shoulder and is one of the bad things that can happen on a manual loading line thus if you ever see a round of military ammo where the head is blue and the other ammo the neck/shoulder is blue this is your warning do not fire it under any circumstances.
 
This was known to occur on 5.56 ammo loaded on manual lines at LC, TW etc and we got a M16 in that had sustained a case failure about every four months when I worked in the Product Engineering section for the Army Small Cal Lab at Picatinny Arsenal.  The upper receiver is bowed outwards and is ruined.  We never had a case of lug faillure on the bolt or barrel socket.  It was estimated that this occurred once every 30 million rounds..