Bolt lift and pressure signs?

zr600

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Ok I have been having problems with my 7mag not extracting brass. So I had a m16 mini extractor installed. Now i can shoot open the bolt like pivot it up to pull back but can’t pull the bolt back have to use cleaning rod to get it open. Now my question is if it was pressure wouldn’t I have heavy bolt lift when first starting to open the bolt or lifting the bolt not pulling it back. This same load never used to be an issue. Barrel is a criterion remage, 430 total rounds, only 9 rounds since I cleaned it last. This is with adg brass, been fired few times. Any ideas would be great.
 

Tripodmvr7

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If you give barrel length, speed achieved with X bullet, charge and COL (base to tip of bullet) then Quick Load can give you an idea of pressure. Case volume will be a bonus.
 

zr600

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I have always used adg brass. 26” barrel, 67.3 retumbo I know I’m .090 of lands, 180berger vldh, it’s about 2900-2920. Oal 3.350. Had less issues in warmer temps this summer then now in cooler weather. No new lot of powder or primers.
 

Tripodmvr7

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Hope you can see the text on the attached file. It can be pressure as the calculation shows close to 59K psi (max 62K).
A good test would be to drop to a lower Node and try a speed of 2810fps. Load should be close to 64.7gr. If that solves the extraction problem then you know the cause. Will a drop of 100fps be an issue with the hunting that you do?

QL calcs giving pressure are not the most accurate, but are good indicators of possible problems.
 

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zr600

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If it’s that hot of a load why don’t I get heavy bolt lift though? And also earlier this summer I wasn’t having issues with the same load. I don’t know I guess really when I change the ballistic calculator to 2810 instead of actually at 2940 it really doesn’t change much.
 

Tripodmvr7

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Have you annealed your brass? To achieve consistency, I anneal my brass after every firing. Google Erik Cortina and see what the serious long range guys do.
 

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