What in the world?

Ive been partial length resizing since first started rolling my own 25ish years ago....the "how to " and why is in my 1st edition nosler reloading manual.my poohseventy HATES neck sized ammo.....suspect bore is slightly off centre from chamber.... and full length resizing works brass heaps and had led to head seperation early on...so have stuck to partial sizing...when I got the .223 and .308 it got same treatment....the BLR wont chamber brass unless its been full length sized and some of it needs to go through an older 30/06 die aswell to squeaze the base in enough for it to chamber easily....which makes me suspect the hornady new dimension .308 dies have generous chamber sizing.

For my 2 cets. I always like to have the rifle present when I'm doing my case sizing to ensure I do the minimum amount of brass working.
I have 243 lever that requires a full length resize to minimum specs everytime. This also means I have to trim the brass every time. Hence I only get about 5 loads out of my brass. I brought a set of picks to test for that internal crack and do so everytime. You can see that ring on the outsize.
Had a trail boss round separate which stated this.

My bolt 243 and lever 358 only get a neck sizing and I can go 5-6 or more uses before I have to trim.
Z

That couldn’t of happened on fireing unless the dents are in the chamber as rased Portions
The brass will always form to the chamber

Unless something happens during a case head Separation never had one
So wouldn’t know

That couldn’t of happened on fireing unless the dents are in the chamber as rased Portions
The brass will always form to the chamber that being said if there was dents in the case before fireing they should be gone now aswell

The case head separation is really bad is the rifle still in one piece if so id have it checked over by a Confident gunsmith
You could of damaged something pretty easy

The dents are the strangest bit
Unless something happens during a case head Separation never had one
So wouldn’t know

@gundoc @greghud might be able to help out more here

Unless Obviously it’s fireformed forward into the Throat which would be understandable as no case head stopping it from moveing forward

I would measure the shoulder headspace on an unfired round. I’ve had hornady brass before that was way too short (like 0.7mm!) underspec when brand new. Would separate or go very close to it on second or third firing. Weights were all over the shop too.

Horrible stuff, if I had to use hornady brass I’d probably quit reloading. With 7mm rem mag Norma is likely your only decent choice.

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Originally Posted by 7x64

I would measure the shoulder headspace on an unfired round. I’ve had hornady brass before that was way too short (like 0.7mm!) underspec when brand new. Would separate or go very close to it on second or third firing. Weights were all over the shop too.

Horrible stuff, if I had to use hornady brass I’d probably quit reloading. With 7mm rem mag Norma is likely your only decent choice.

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Yeah I think ive Officially used Federal for the last time aswell last week hornady and federal are both now on my shit list

A use ether norma or lapua depending on caliber and tell the few mates i reload for the same

I have experienced a similar problem myself when shooting in fine misty rain, dimples on the case and a partial case head separation but no excess pressure signs. It was tiny water droplets which prevented the case from adhering to chamber wall when fired. I dried the chamber and ammo and the problem immediately disappeared. A simple fix to a simple problem!

case head seperation, the reason the case has collapsed in the shoulders is when the front of the case becomes detached from the rim, it becomes part of the mass that is being forced out the barrel by the expanding gasses.
it is pushed forward untill the neck seals against the start of the rifled section of the barrel the gap inbetween the case and the chamber wall becomes a low pressure spot and the case collapses as the expanding gas is forced out the barrel, trying to force the brass case out the barrel. thats why it often takes some effort to remove the front half of the case, as it is wedged into the rifling. it is quite common to see.
Greg

Quote:

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Originally Posted by gundoc

I have experienced a similar problem myself when shooting in fine misty rain, dimples on the case and a partial case head separation but no excess pressure signs. It was tiny water droplets which prevented the case from adhering to chamber wall when fired. I dried the chamber and ammo and the problem immediately disappeared. A simple fix to a simple problem!

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reminds me of the "field proof test" for a 303, was to coat the case of a standard cartridge with oil then fire to simulate an over pressure load.
Greg

@Bagheera this may be of interest

Thanks mate !

I'm used to knowing the answers so this is a bit of a puzzle for me ...

That's a dooozy photo on the first page, eh ?

My vote is that the case was sized too short and separated, then under inertia jammed forward into the shoulder.
I dont think pressure of gas outside the case could collapse it into dimples because it would be balanced by pressure inside.
The haze on the separated base suggests the body has been sized a long way back towards the belt.

Sizing too short has happened to me when the jaws of the case holder on the co-ax press dont open properly and the base hangs up too high so it come out about .200" short. Usually pretty obvious. Maybe you could get that if you used the wrong case holder like a 308 holder and the case went partway into it.
Or was this case actually fired in a 300 win mag chamber which is 0.160" longer ?

If the case was sized too short then measuring the two separated pieces should give < 2.500".

Anyway it's best to go to the reloader first. He might know straight away what it is.