Case Head Separation

[Casimirblue]

Ever since my first one , I now try to inspect for possible case head separation. Generally comes from over bumping the shoulder which I am guilty of. These are just at 5 firings. 6XC Peterson Case. Its completely my fault.

Borescope / No Mirror. When I see the line on the outside of the case, I weed out for a look.

 

[MagnumManiac]

It's not just overworking the shoulder length, it's also overworking the case body that causes this too.
A body die can eliminate this, they do not displace brass the same way as a conventional die and also work them less.

Redding dies seem to work the brass the least, both in body sizing and neck sizing, mine move the neck .002" on average. Which is what I want when I order Forster dies with honed necks. They also size a minimum amount in the body too.
When you overwork the body, that brass is displaced into the shoulder, where it is then worked more to push it back.

Cheers.

 

[Seabeeken]

I recently wore out some hornady brass. Got some lapua and its a tack driving rifle again. Had 2 seps with it

 

[Hugnot]

Great pics - shows what's happening.

Upon repetitive sizing brass become more "work hardening" and cases need to be trimmed because it gets longer. The brass flows forward increasing length. How many firing cycles to get to ,the point where brass thickness just forward of web is reduced to the point of separation occurs is sort of speculative but logically it should happen. Upon all that sizing the brass become less ductile and thinner because of work hardening and stretching then - separation.

I have not made comparisons of the degree various dies work cases. I use a Redding small base body die for resizing once fired .223/5.56 brass for my .20 P rodent rifle & I only do this 1 time. The body die does not size the neck. The Redding type S F/L .223 sizer with a .226 bushing does not size the base enough and 1 out of 10 used once fired .223/5.56 cases get stuck in the chamber enough so the rim gets ripped off & extraction needs to be done with a cleaning rod. My RCBS .223 F/L die sizes the once fires bases enough to enable normal extraction.

I like Forster F/L dies & after I check things out with brass & chamber I send them back to be honed out. Forster apparently has increased their charge to do this - just under $30. Lapua brass is real pricy but cost differences are mitigated when brass life is considered.