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Thread: Low pressure signs

  1. #1

    Low pressure signs

    Evening all. Had an interesting range session yesterday with 55gr Nosler BT with a starting load of 45gr of H414. Shot a one hole group but the primers were slightly proud of the pocket upon ejection and having double checked powder manufacturers data and Quick Load there is no way this can be over pressure and certainly no other signs on case or issues with bolt.

    I have heard of this symptom with low pressure failing to seal the primer and allowing it to be pushed back by the gas through the flash hole. Am I correct? Am I missing something? Are there any issues with this?

    Cheers fellas.

    Penyard

  2. #2
    I had primers easing out of the primer pockets when I knocked the shoulders of the brass 8 thou too far back some years ago. I sometimes check fired brass for this by placing the fired case, head down on a sheet of glass. If the primer is backing out, the case will rock back and forwards on the primer.

    I suspect you've adjusted your dies for one vintage/brand of brass and then run new brass through the die.

    Regards JCS

  3. #3
    Get your rifles headspace checked straight away!! That's what happened with my rifle before things went badly wrong. You could buy a headspace gauge and do it yourself really easily

  4. #4
    Quote Originally Posted by srvet View Post
    Get your rifles headspace checked straight away!! That's what happened with my rifle before things went badly wrong. You could buy a headspace gauge and do it yourself really easily
    No need to wring the hands and check the headspace. I agree: it is most likely low pressure and has nothing to do with the headspace of the weapon.

    Why is it only the Brits I've met have their headspace suddenly go bad?? You never hear of an American shooter saying that the headspace on their rifle went out over night.~Muir

  5. #5
    Thanks chaps. I would be surprised if it was a head space issue as it is neck sized brass that has been fired in that chamber before. However, I asked the question as I genuinely had not experienced this before so will check head space and case dimensions to be on the safe side.

    ATB

    Penyard

  6. #6
    Quote Originally Posted by Muir View Post
    No need to wring the hands and check the headspace. I agree: it is most likely low pressure and has nothing to do with the headspace of the weapon.

    Why is it only the Brits I've met have their headspace suddenly go bad?? You never hear of an American shooter saying that the headspace on their rifle went out over night.~Muir
    Perhaps it's because we have a history of using .303 rifles with removable bolt heads and stretchy actions. I doubt the Germans have many headspace worries either.

    My AI AW will also suffer from primer push-back if the load is too low.

  7. #7
    Quote Originally Posted by Penyard View Post
    Thanks chaps. I would be surprised if it was a head space issue as it is neck sized brass that has been fired in that chamber before. However, I asked the question as I genuinely had not experienced this before so will check head space and case dimensions to be on the safe side.

    ATB

    Penyard
    Penyard.

    Thanks, but I don't follow your post and subsequent comments at all. I suggest you get someone local to you to check over what you are doing. What cartridge are you reloading?

    Regards
    JCS

  8. #8
    If you have zero headspace, surely there is nowhere for the primer to push back too

  9. #9
    Quote Originally Posted by srvet View Post
    If you have zero headspace, surely there is nowhere for the primer to push back too
    +1. Thanks JCS

  10. #10
    On the headspacing side of things.... you haven't just changed to a Lee Shellholder by any chance?

    When developing the load for my Sako A1 based .20Prac last year I was getting cratering on my primers at a fairly mild powder load.... back down to the riflesmith expecting to have the bolt worked on and we tracked it down to my cases having the shoulder bumped more than expected giving the extra headspace..... which turned out to be down to the Lee s'holder I'd used having a non-industry standard deckheight... ie it was a nadge lower allowing the case further into the die.

    A search on google turned up that Lee have a bit of a rep for this.... switched to an RCBS shellholder and problem solved.

    So it's not always the obvious culprits....... sometimes.

    Cheers

    Fizz

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