Shooting Sakos (and others) - the two-group phenomenon

Discussion in 'General Sako Discussions' started by icebear, Aug 17, 2019.

  1. icebear

    icebear Well-Known Member

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    Today I was checking the zero on the new scope for my L461 carbine and ran into in issue I've seen many times before, especially (but not exclusively) with Mannlicher-style rifles and carbines. In a string of 5 or 10 shots, the hits will group themselves into two distinct clusters an inch or more apart. Two touching in one group, then two or three together in another, then back to the first group for a couple of rounds, etc. Now I am fully aware that this could be some kind of odd shooter error, but it seems strange that I get two distinct clusters in a string of shots, with hits going back and forth between the two.

    Have any of you run into such a phenomenon, and do you have any idea what might cause it. And yes, the action screws are tight. I plan to do more testing with varying the tension on the barrel band screw, since I have seen in usually reliable sources that this can have a significant effect on accuracy.


    Any relevant thoughts or experience?
     

  2. ricksengines

    ricksengines Sako-addicted

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    Heat can always affect POI. When I am shooting for group while testing out a load I always wait a few minutes between shots to give the barrel a chance to cool down.

    rick
     
  3. Foxhunter223

    Foxhunter223 Well-Known Member

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    I had this same problem with my L461 in 223. Turned out to be the Leupold scope was moving internally every shot. Leupold fixed it for me and now shoots nice round groups again, well when I do my bit that is.
    Pete
     
  4. icebear

    icebear Well-Known Member

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    Now that you mention it, one of the times this happened to me it turned out the scope bases on an FN action were loose. I had carelessly mounted the scope with the screws that came with the bases without checking the threads. Turned out that the mount had metric screws and the gun was tapped for the usual US 6-48.

    Thanks for the suggestion - I'll check it out but I kind of doubt it's a scope problem this time since the scope is a Zeiss Diavari. Rings are regular Sako and they are dead tight.
     
  5. Rick Omohundro

    Rick Omohundro Member

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    It certainly could be the scope or mounts. The only time I've experienced such is with a 591 model with the separate recoil lug. That rifle shoots two distinct groups, very small, although less than an inch total. It has had a few scopes on it so I'm comfortable it is because of the recoil lug moving.
    Good Luck,
    Rick
     
  6. kirkbridgershooters

    kirkbridgershooters Well-Known Member

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    I have had people experience internal problems with all brands of scopes, but I don't know that any scope will internally change and continue to shoot 2 groups back and forth. The odds of that happening are possible but astronomical at the same time. There are so many anomalies in shooting with scopes, mounts, bullets, powder, shells and countless other variables, when you think about it, you are darned lucky to get a rifle to hit anything...
     
    deergoose likes this.
  7. icebear

    icebear Well-Known Member

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    An update - I put some rounds downrange last week with the .222 carbine, this time at 100 yards. Group dispersion was normal with Remington ammo and Lapua ammo gave me a nice little half-inch triangle. So, the two-group phenomenon disappeared as mysteriously as it appeared. I have two possible explanations. First, random shooter error happened to produce a group alternating between two distinct points of impact. Second, the one factor that changed was that I loosened up the barrel band by half a turn. Barrel band tension is known to affect accuracy in full-stock rifles, so adjusting the screw tension on the barrel band could have been the key. In any case, I'm quite pleased with a full-stock carbine that will shoot a half-inch group. We'll see if anything similar happens with any of my other rifles.
     
    XTrooper, Norway.375 and Sean Hodges like this.

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