primers flattening with no other signs of pressure?

Bigeclipse

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Aug 10, 2012
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Hi everyone,

I am trying to work up a load with a rifle (7mm08 using 131 grain hammer hunters, lapua brass, Winchester large rifle primers and varget) and I am noticing that the primers are flattening even at lowest book loads but I am getting no other pressure signs such as stiff bolt lift, ejector marks, high velocities, and cratering (there is just a touch of cratering but it could just be the firing pin mark because I have definitely witnessed way worse cratering so I am not 100% on this).

What are your thoughts?
 

ButterBean

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Feb 5, 2012
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Location
West Terre Haute Indiana
Hi everyone,

I am trying to work up a load with a rifle (7mm08 using 131 grain hammer hunters, lapua brass, Winchester large rifle primers and varget) and I am noticing that the primers are flattening even at lowest book loads but I am getting no other pressure signs such as stiff bolt lift, ejector marks, high velocities, and cratering (there is just a touch of cratering but it could just be the firing pin mark because I have definitely witnessed way worse cratering so I am not 100% on this).

What are your thoughts?
Do you have a picture, and if there were no other signs of pressure, let her eat, most likely a bad batch of primers
 
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Bigeclipse

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Rardoin

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Jul 22, 2020
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South Louisiana
Try rubbing a little case lube or light oil on the body and firing one. If there is excessive clearance between the case head and bolt face the primer will protrude back into the bolt face before the case slides back once released from the chamber walls as the pressure drops a little. Lubing the case slightly will allow the case to thrust backward to the bolt along with the primer then expand completely to the chamber walls. If excess clearance (from undersized brass ie- shoulder too far back) is the culprit that fired case should show no primer flattening. If that be the case then readjust your sizing die for less shoulder 'bump'.
 

Bigeclipse

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It looks seated way to deep from that angle, are you uniforming your primers pockets?
I am not. I heard lapua brass was pretty uniform for primer pockets. I am seating as deep as my hand seater allows. That is how I was taught and never had an issue. Every primer I have ever seated looks that deep. Have I been doing it wrong?!?
 

Bob Wright

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Jan 23, 2018
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Litchfield Park, Az.
That picture shows the unfired primer seated deep. How deep? Curious...
Also agree to look at headspace again and verify bump.
I had a primer uniformer go bad once and scrapped some brass.
 

Bigeclipse

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Aug 10, 2012
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Try rubbing a little case lube or light oil on the body and firing one. If there is excessive clearance between the case head and bolt face the primer will protrude back into the bolt face before the case slides back once released from the chamber walls as the pressure drops a little. Lubing the case slightly will allow the case to thrust backward to the bolt along with the primer then expand completely to the chamber walls. If excess clearance (from undersized brass ie- shoulder too far back) is the culprit that fired case should show no primer flattening. If that be the case then readjust your sizing die for less shoulder 'bump'.
I have been measuring shoulder bump with my lock n load set and I have been about 3-5 thousandths bump as I do not want a stuck case during a hunt and would rather overwork the brass. Is that too much?
 

Bigeclipse

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No I'm not saying that your doing anything wrong at all, it just looks really deep from that angle
it is as deep as the primers can go and they all look like that. Maybe a funny angle or maybe they are all too deep? Can too deep primer be a problem?
 

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