Helping for solving a problem with 12.7 mm

I got some photo from my friend.

Headstamp?

Why do these problems occur?

Case head separation (the lower image with the short piece of case) is usually the result of too large head space.
Mainly due to lack of maintenance or to be exact wear of guns. Not unusual in scenarios with non-state actors.

The case on top which appears longer is somewhat unusual. In my view not typical for a too large headspace but maybe the true experts here can shed more light on this one. Unless this one was cut off by somebody and it is no gun failure.

Why do these problems accur?

As said:

Headspace.
The distance from the bolt face (when locked) to the shoulder in the chamber is too large.
The gas pressure pushes the forward part of the case against the shoulder, while the cartridge base is pressed rearward against the bolt face. The steel of the cartridge case is by far not strong enough to take up this force alone and as a result the case ruptures in the way you show.
The cause of too much headspace usually is a worn wepaon or using a bolt that does not belong to the weapon.

To illustrate it a bit:
https://www.google.de/search?q=case+head+separation&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjs6bHYxPXeAhVLzKQKHSOPA0AQ_AUIDigB&biw=1920&bih=959

Another possible scenario for cases separating, especially with steel cases, would be the gun chamber. If the chamber is not hard-chromed and is getting rusty(especially with corrosive priming) from lack of proper maintenance, cases begin sticking badly. Sometimes, so stuck that, with a strong extractor and thick enough rim design, the case can be pulled apart.

BTW, were the shown cases inside this crate???

Thanks for your helping.

I did not understand your question, EOD

He’s asking if the rounds of ammunition in the pictures comes from the wooden crate marked 12,7 B-32.

Ole

Yes.it belongs to wooden crate.

Do you have photos of the 2 tins that were inside ?

I dont have them because I got photos from my friend and have to want him that send me.