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  #1  
Old 08-10-2019, 10:10 PM
sigguy552 sigguy552 is offline
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Default 300wm MK248 Mod 0 - Signs of overpressure?

I recently started shooting an old batch of what I believe to be mk248 mod 0 ammunition(FC 93 marked brass) and was having a bit of trouble extracting. When I got home, I noticed my brass had these round marks in the back which after a bit research, appears to be extractor impact marks from the brass being shoved back into the breach face i.e., excessive pressure.

https://photos.app.goo.gl/V3GPWUH6MLwSTYsK6

I heard this is rather normal for this round and besides shortening the barrel life, is still ok to shoot. Can the pros on here give me their 2cents? I'm shooting this out of an AI AWM if that matters.
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Old 08-10-2019, 11:27 PM
sigstroker sigstroker is online now
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There are a bunch of other sign of too much pressure - flattened and/or cratered primers, stiff extraction, bright ring on the bottom of the brass near the belt, etc. Do some research and see if any of those signs are present.
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Old 08-11-2019, 8:56 AM
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It looks like the picture shows brass flow into the hole of a plunger type ejector. The brass flows into the hole making a high spot on the brass which is then wiped off as the bolt rotates.

It is a sign of excess pressure but I am surprised that the primer does not show more flattening or leakage. It could be very soft brass.
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Last edited by Fjold; 08-11-2019 at 9:00 AM..
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