Id -
I had a 'different' situation that involved 'noticeably' less velocity (-200 fps) than I HAD BEEN getting. I am going to drastically reduce this story to get to THE answer.
This was @ 1990. I was shooting a 270--130 gr.--with a load that was KNOWN for an honest 3100 fps. I was shooting the same components - maybe a different lot # - BUT some new cases from a reputable maker. I had the loads ready so when I went to chronograph some other stuff, I thot I'll just check those loads out of 'curiosity'.
CURIOUSLY what had been going 3100 was ONLY 2900 ! ! Shaking my head, scratching my head ? ? ? LONG story short. I double checked the powder---and---primers separately. This took a couple of weeks of loading and graphing. Then, as a last resort) I RE-USED those same components in OTHER brass.
The load was compressed so there was NO adding powder to the charge.
Bottom line - the NEW brand of brass cases was THE culprit. Yes! !- I lost 200 fps in those cases ALONE.
I have since used that BRAND of brass with NO problems. There was some lot/lot variation or problem. For a few years I refused to buy that brand but 'eventually' I tried some others and they work fine.
I know this doesn't answer your ? but it shows queer stuff does happen.
Jerry
