Thread: When a belted case head separates

Does this happen right at the junction of the belt and main body or is it a little way further forward like in unbelted cartridges ?

I'm wondering where you measure case looking for expansion of the base as a sign of too much pressure. Do you measure on the belt or on the body in front of it ? Just right at the edge of the belt under the step or a few mm further out ?

Case separation usually occurs about 10mm ahead of the internal web in the case, where the case walls are starting to thin. The case design (rimmed, rimless, or belted) doesn't make any difference.

I measure inside the extractor groove with a blade micrometer. Don't have any belted mags so cannot comment on them.
Be careful though you can draw incorrect pressure conclusions with this method.
I take 2 measurements in exactly the same places each time. Use the headstamp as reference.

you will usually see a line there first. or use a paper clip with a 90 degree bend on the end to feel for it. but I tend to see it on the outside first. I would of thought 5mm above the belt. somewhere about there.

For measuring case expansion on a belted magnum measure just in front of the belt.

About there somewhere

Take the cases into a dark room and shine a tiny single bulb led into the case. Any sign of incipient head separation will be easily seen as a dark recessed ring a few mm above the web.

Belted cases should be headspaced off the shoulder rather than off the belt.

Originally Posted by Ham 7mm

Attachment 143918
About there somewhere

How many times fired?

About 6 but combined with new hot batch of adi powder giving me an extra 100fps unexpectedly was the thing that caused it.