Shifting Point of Impact

Discussion in 'Long Range Hunting & Shooting' started by memyselfni, Mar 17, 2012.

  1. memyselfni

    memyselfni Active Member

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    Hi all, I have just started loading for a 2506 in a tikka t3, found an accurate load with 115 Bergers, having problems with shifting point of impact between groups, does anybody have any ideas as to why this may be happening? Please see attached Photos. Scope is a leupy vx3 2.5-8 if this helps shot off sandbags front and rear

    Thanks
     

    Attached Files:

  2. Scot E

    Scot E Well-Known Member

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    Could be lots of reasons.

    Does the picture orientation show the way the targets were hanging when they were shot?

    What distance were these shot? Sure it wasn't just wind drift?

    How is your parallax and do you feel like you have consistent eye placement behind the scope each time?

    VLD bullets are sometimes tough to get consistent if you are seating to a specific OAL. If you aren't already you may want to measure OAL to the bullet ogive as this will give you a much more consistent seating depth.

    Scot E.
     
  3. sp6x6

    sp6x6 Well-Known Member

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    My guess same as above, doubt that scope has parallax adj. Next time shooting , line head up more to left, fire 2, then same on right, or up down. See if that sends your groups to same spot, rifle looks like it will shoot. If that is it may want a check piece or stock pack and work on head placement
     
  4. memyselfni

    memyselfni Active Member

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    The targets were hanging with the dot at the bottom, there was a mild wind that was blowing from time to time, so i am not so much concerned about the horizontal placement of the groups, its the 1.5 minute vertical shift that i am trying to sort out. Loads consisted of Federal brass, federal 210 primer, 57.5gr of retumbo and a berger 115 Hunting VLD seated to jump .006. have been measuring oal from the ogive with the hornady tool. Groups with this load seem to shoot between .3 and .7 for 3 shots at 100m, worked out over about 15 groups.

    Thanks
     
  5. barnesuser28

    barnesuser28 Well-Known Member

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    were you cleaning between each group? that is the only possible problem i can think of :/
     
  6. memyselfni

    memyselfni Active Member

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    No i didn't clean until after the last group. I am really pleased with the group sizes especially for a 7.5lb rifle/scope combo, just need a bit more consistency with POI. its a pretty mild load only doing around 2850 on my chrony. Do you think that going to a B&C composite stock will make a difference? only thing i can think of is maybe a different position of the front stock from group to group
     
  7. barnesuser28

    barnesuser28 Well-Known Member

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    now that you mentioned stocks your barrel could be rubbing on some part of the stock. take a piece of paper and run it between the barrel and forend to check if it is free floated. it could be different positioning of the front of the stock but check to see if it is free floated
     
  8. memyselfni

    memyselfni Active Member

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    its free floated until about 3 inches in front of the action, but barely. I made a typo before, i meant to say positioning of the front bag. Now that i recall, the first group, that shot high i had the bag positioned pretty much under the action.
     
  9. barnesuser28

    barnesuser28 Well-Known Member

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    that is probably the problem
     
  10. memyselfni

    memyselfni Active Member

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    Do you think a stiffer stock thats free floated more will be a bit more forgive in regards to rest placement?
     
  11. barnesuser28

    barnesuser28 Well-Known Member

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    i would think it should also try glass bedding the action to the stock i am sure that and free floating the barrel would help
     
  12. memyselfni

    memyselfni Active Member

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    Is this necessary if i got to a bell and carlson with a full length aluminium bedding block? think im going to upgrade to a Bushnell 6500 2.5-16.
     
  13. barnesuser28

    barnesuser28 Well-Known Member

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    i dont think so but i would start a thread asking about it, you would get answers from people who have "been there, done that"
     
  14. Scot E

    Scot E Well-Known Member

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    By the looks of things your gun wants to shoot. Before you look to drastic measures I would shore up your shooting from and bag positioning and make sure your barrel is clean before all the groups. Typically you will see your groups start to fall off as your barrel gets too dirty so you will know when to stop and re-clean.

    If this doesn't work I would see if you can clean up the barrel channel to make sure things are completely fee floated. Sometimes just a bit of sanding will make a big difference.

    HTH,

    Scot E.