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Thread: Rounds jamming into lands

  1. #1
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    Rounds jamming into lands

    Evening guys, ran into a problem this afternoon with a few rounds jamming into the rifling. I rechecked the coal and ojive measurements and they match near perfect with the rounds that are chambering fine.
    I've done a jam measurement in the past and they're seated 25 thou off jam. Brass was all necksized then sorted to right length.
    I fired a couple and the bolt was stiff to lift, is this indicaticating a problem in the neck or shoulder?

    I'm new to reloading so won't be surprised if I'm missing something pretty obvious, any help or thoughts would be great.
    Cheers

  2. #2
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    In addition to the above... neck tension may not be enough also.

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  3. #3
    Almost literate. veitnamcam's Avatar
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    What is your indicaction they were jamming into lands? did you stick a round in the chamber and try to eject a live round and have the bullet stick in the barrel?
    Your lands dont move back and forward so something in your measurements is asmiss.

    Need more information.
    tetawa, Moa Hunter and mimms2 like this.
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  4. #4
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    are you 100% positive its projectile jamming into rifling???? eg did you open bolt and find marks on projectile or COULD it be the sizing die loosened slightly and case is tighter than normal somewhere else,eg shoulder is rubbing.....
    Ive been caught by it before is why I mention it.

  5. #5
    Almost literate. veitnamcam's Avatar
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    Have re read your post.
    Are you reading stiff to close the bolt as jamming in the lands? If so this may actually just be that the cases you have neck sized are due a shoulder bump.this will also explain slight stiff opening of bolt.
    Moa Hunter and keneff like this.
    "Hunting and fishing" fucking over licenced firearms owners since ages ago.

    308Win One chambering to rule them all.

  6. #6
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    Heavy bolt lift is probably due to those rounds being over-pressure, due to the projectile being jammed (so higher pressures being generated before the projectile will move).

    But my first question is...How do you know the rounds are jamming into the rifling?

  7. #7
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    Na no signs of pressure and were 2grns lower than max load in hornady manual. rounds were tight to chamber and leaving rifling marks on the projectiles.
    Rifle is a fierce 24inch 7mmRM, rounds are 162 eldx and 66.5grn upto 68grn h-1000,3rd reloading aswell as annealed and sorted to right length.
    Unsure on velocity, concentricity and havnt been neck turned.
    mimms2 likes this.

  8. #8
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    Ok jammed causing the high pressure males sense to me

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    It is plainly obvious. He is not shooting a .308
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    Use enough gun

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    Name:  20210914_200627.jpg
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  11. #11
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    Quote Originally Posted by veitnamcam View Post
    Have re read your post.
    Are you reading stiff to close the bolt as jamming in the lands? If so this may actually just be that the cases you have neck sized are due a shoulder bump.this will also explain slight stiff opening of bolt.

    Yea I was thinking along these lines of shoulder bump issue. Is the only way to really figure this out with a headspace gauge for the comparator?

  12. #12
    Almost literate. veitnamcam's Avatar
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    Quote Originally Posted by kayneb View Post
    I dunno what that is but it is not a mark from your lands.
    Looks like a dent?
    "Hunting and fishing" fucking over licenced firearms owners since ages ago.

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  13. #13
    Member Micky Duck's Avatar
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    nah...felt tip pen a tight round..chamber it a few times and see where its touching..

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    Quote Originally Posted by ripped undies View Post
    just one mark or are they equally spaced around projectile
    Just the 1 deep gauge like in pic but there is a bit of scuffing and tiny dents around the projectile

  15. #15
    Almost literate. veitnamcam's Avatar
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    Take a fired case that chambers easily and one of the ones that was stiff to open and measure them both on the shoulder....you could use say the 45 cal comparitor or whatever just use the same on each.
    Set up fl die to just bump back to the lenght of the fired case that chambers easily to up to minus 2 or 3 thou less max.
    mikee and Moa Hunter like this.
    "Hunting and fishing" fucking over licenced firearms owners since ages ago.

    308Win One chambering to rule them all.

 

 

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