First case head separation

[Dmagna]

First one, 257 bee. Shooting Berger 133 EH with retumbo. 3200fps

 

[parshal]

That separation looks way high up on the case. They're usually just above the case head where the brass sticks out of the chamber. Something looks very weird about that one.

 

[Dmagna]

Yeah. I don't get it. Bad brass maybe

 

[nhenry]

Is it headspaced on the shoulder or the belt?

 

[Dmagna]

Belt

 

[RegionRat]

The belted magnums often fail right there, so I wouldn't say it is unusual.

Depends on your chamber, dies, and sizing habits, as well as the brass.

The third case in the photo would be a cool candidate to section if you have the facilities.

How many cycles on this brass?

 

[Dmagna]

The belted magnums often fail right there, so I wouldn't say it is unusual.

Depends on your chamber, dies, and sizing habits, as well as the brass.

The third case in the photo would be a cool candidate to section if you have the facilities.

How many cycles on this brass?

5

 

[Turpentine21]

I ran into that years ago using machine gun fired military brass and not having enough lube in the neck when I full length sized. I would struggle to get the expander ball to come back through. Thus stretching the case at that point. Plus the machine gun had already worked some of it pretty hard with excessive headspace. Possibly not the issue but I figured I would share.

 

[can1010]

seen this many times with belted mag cases. usually when the brass is new with a really short shoulder datum measurement, the case stretches real bad right there instead of taking brass from the neck to make up for the short case that head spaced off the belt.

necking the new brass up and adding a false shoulder will help with this problem as well as setting your dies to headspace off the shoulder as if the belt don't exist.

 

[Teekerguy]

another option is to neck size and bump shoulders as needed not ideal but will work

 

[memtb]

I had one on my AI, very similar location, about 10 years ago….my first and knock on wood, my last!

I had 10 firings on it…..how many times for yours? Never mind, didn't read all posts very good! memtb

 

[MagnumManiac]

Classic separation caused by bumping the shoulder too much. The double radius shoulder always measures incorrectly with a comparator. Try reducing the amount of bump, .0015" is what my measurements are on 257, 270, 300, 340 & 375…any more than that is too much.
I neck size only for 3 firings on all belt d mags, I don't get separations.

Cheers.

 

[Aussie Hunter Steve]

Looks like your necks have grown too, backing up what Magnum has just suggested.

 

[Mike Matteson]

That separation looks way high up on the case. They're usually just above the case head where the brass sticks out of the chamber. Something looks very weird about that one.

That is my thinking, but what do I really know. Most of case separation I have are just above the belt or at it. Never seen anything like that. On my belted mag I genereally only neck size until the brass won't chamber, and only set the should back on a .002 thousands. I generally lose my case to primer pockets enlarging.