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Thread: Vertical Stringing

  1. #1
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    Vertical Stringing

    Have been frustrated by a mates 280AI recently, while developing a new load for the 150gr LRAB’s, due to the unavailability of RL17. After thinking that we had it dialled-in, it will string shots vertically, each getting progressively higher, in the order of 4-6 inches higher. Typically, the first two shots have the same POI, but after that things go to shit. A first shot from a cold barrel will always be spot on.

    I always thought that this sort of vertical stringing was due to bedding? But we can’t see anything wrong with it. Action screws are consistently tight etc. We did try some forend pressure, but that made no difference.

    Rifle is a Brno 600ZKK, 24” Shilen, bedded etc with Vortex 4-16 HS scope.

    Anything obvious we may have missed? Short of re-barrelling the bastard thing…..
    Last edited by gqhoon; 17-10-2016 at 07:40 PM.

  2. #2
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    Have had same thing and its been oil under the bedding. Make sure the bottom of action is dry
    I always store rifle with some tissue stuffed up chamber now to prevent any oil running down barrel and getting under action while stored

    It's always intrigued me the Forbes rifles are full length barrel and action bedded....go figure

  3. #3
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    Sounds like a barrel heat issue, some have no issues, others have minor changes in poi and the special few do exactly as you describe, not really an issue with a hunting rifle as the first two shots/deer are usually enough to carry.

    It's up to you if it's something you can accept.

    Two accurate shots is well enough for most to hunt with, especially if a 5 min cool down gives you another two.
    WallyR likes this.
    A big fast bullet beats a little fast bullet every time

  4. #4
    R93
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    Yup. Shoot a group cold barrel every shot and if it has required poi, it is most definitely a heat issue. If it was bedding it would be very unlikely to track back to zero every time.

    Sent from my SM-G935F using Tapatalk
    WallyR likes this.
    Do what ya want! Ya will anyway.

  5. #5
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    Thanks for the feedback, it is much appreciated.

    Will attempt a cold barrel group this weekend, weather permitting, and see how we go.

  6. #6
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    Has the rifle shot properly prior to this new load development and bout of shooting?
    Are you doing the shooting or is he?
    How many groups have shown this pattern? How clearly is it shown? What I mean is, are you seeing a pattern, or are you looking at random results and ''seeing'' this pattern; ie, maybe its a crap load and your seeing patterns in random results.
    Try the cold bore group.
    But also, make sure to get into the same position after each shot, if the butt is not into the shoulder the same height each time, and if the rifle is working its way back off its rest it can have a similiar effect, if you are getting beaten back by recoil and not getting into position properly each time.

  7. #7
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    Brno issue. Have seen this on others of the same general breed, first spot on - others minute of barn door. Never could work out why, possibly some heat issue with action or barrel fitment or something else weird.

    Easiest option, was find another toy to play with and save my back at the same time...
    R93 likes this.

  8. #8
    Member rossi.45's Avatar
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    my Brno .308 use to start stringing shots up the target by shot number 3 . . . that was with the factory forend pressure point, cold bore shot was always as before. A decent glass bedding job fixed that, now its consistant from cold to way to hot to hold onto when goat shooting back in the day.

  9. #9
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    Another option to try is give it half a grain more powder.
    nor-west likes this.

  10. #10
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    As above I have a CZ537 in 7x64 the 537 its the model between the Zkk600 and the CZ550 anyway it had vertical stringing with 53.5 grains of W760 with the 150 gameking, next load of 54 grain gave a group of .164. Brian and I were amazed the difference 1/2 grain of powder made.

  11. #11
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    The one I played with was a pig of a thing, another 1/2 a grain would have probably split the bastard in half. It was a sticky bolt special with most factory loads. Cold bore, same place every time but not ideal having a brew between each shot. I suspect that one wasn't typical of the breed though. They do seem to be a particularly fussy setup though, the BRNO's...

  12. #12
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    Quote Originally Posted by Echo View Post
    Have had same thing and its been oil under the bedding. Make sure the bottom of action is dry
    I always store rifle with some tissue stuffed up chamber now to prevent any oil running down barrel and getting under action while stored

    It's always intrigued me the Forbes rifles are full length barrel and action bedded....go figure
    Echo I store mine upside down if I know it's not going to be used for a while. Stops the oil run thing
    That's barrel down with a towel to protect the muzzel from damage

 

 

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