The importance of scope and barrel alignment

Discussion in 'General Airgun Chat' started by athelas, Mar 1, 2019.

  1. athelas

    athelas New Member

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    Hi all

    I thought it would be interesting to find out general opinion on what to me is the thorny question of whether my scope is properly aligned to my barrel, and if not what - if anything - do I do about it.

    The advice you get is just stick your scope on the gun, zero at x yards and away you go. But, I think we will all agree that if there is any significant misalignment between scope and barrel, your pellets trajectory well never correspond to the line of sight - except at the first point of zero. You will always find pellet drift - it starts on one side of the line of sight, and drifts across that line to the other side, as it passes the first point of zero.

    So I think there are 3 choices:

    A. forget about it (most people's choice)
    B. use shims
    C. use laterally adjustable mounts

    I don't sleep well if I have chosen A. B and C are fiddly to say the least.

    Comments?
     
  2. blacklab

    blacklab Active Member

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    adjusable mounts simple
     
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  3. SteveC200

    SteveC200 Active Member

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    As Blacklab says, get adjustable mounts.
     
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  4. Dan Smith

    Dan Smith Active Member

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    If I had laterally adjustable mounts I would definitely mess it up. A receipt for disaster.

    When I adjust my horizontally adjustable mounts it’s very imprecise but easy to resolve by fine zero - can’t do that with lateral adjustment.....
     
  5. Alanok2002

    Alanok2002 Member

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    Adjustable mounts are great i use them to zero my gun after ive mechanicaly centered the crosshairs
     
  6. Cooper_dan

    Cooper_dan Active Member

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    Option A isn't really a real option on this forum (at least I don't think it is). I've found that most people who are happy to just leave it are generally plinkers or casual shooters. Target shooters won't leave it.
    The first thing to try is rotating your mounts. Try flipping them round so the screws are on the other side, or swapping front and rear. This gives you 8 configurations. This might not completely fix the issue, but you will probably find each is slightly different, and hence one will be best.
    This way if you do have to shim, you can shim the minimum amount. This is what I've currently got going on.
    Adjustable mounts are the best option.
     
  7. nemesis

    nemesis 55yrd standing expert, or was it 8 or 9?

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    For lateral adjustment to optically zero your scope, this can be done by tweaking the barrel. On the Steyr it's simply done by undoing the grub screws and re tightening whilst indexing the barrel in the desired direction. It's time consuming but effective, I got mine to within 2 clicks on a 1/8th scope. With regards to shimming the scope my advice is don't unless you want a stressed and bent scope.
     
  8. MickyFinn

    MickyFinn I❤HFT

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    Option A all the way for me :p
     
  9. beaker

    beaker Member

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    I use BKL mounts, no problem.
     
  10. Adam

    Adam Well-Known Member

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    Option C, but you forgot option D: buy a gun without a bent barrel or action :)
     
  11. athelas

    athelas New Member

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    That's very interesting - thanks for your contribution :) I thought adjustable mounts are the best option - but they are a pain to get right. I have used Sportsmatch ATP66 2 piece adjustable mounts (that adjust both elevation and windage). I have found with these that a slight turn on the adjustment screw can make a big difference, and you can't adjust horizontal alignment without affecting vertical alignment - and vice versa. Do you have a preferred model of mounts that work for you?
     
  12. athelas

    athelas New Member

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    Very interesting. I have a Steyr LG110, and I didn't realise you can "tweak the barrel". I don't think this is demonstrated on Steyr's own maintenance video series?? !! I guess I will have to google that.
     
  13. vangard

    vangard Member

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    Are you talking about cross over?.
     
  14. athelas

    athelas New Member

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    Hi vanguard - sorry for late reply! The point I am making is simply this - that in reality, no scope and barrel are in PERFECT alignment. Therefore, however you adjust the windage on your scope, the line of sight and the trajectory of the pellet can only be made to meet at one point. As long as the imperfection between the scope and the barrel is small enough, the effects of this misalignment can be ignored. But in my experience, if I optically centre the reticule in my scope, then stick the scope on the gun, and shoot at a vertical line 8 yards away, the pellet is striking about 5 - 10mm to one side of the line. Therefore I have scope misalignment, and I think this is enough to introduce an error when competition shooting, which is going to be significant. In my example, if I move my vertical line further away, the pellet will either start to move towards, or away from the line - depending on the nature of the misalignment. If on the other hand, the scope and barrel are perfectly aligned, the pellet will always strike somewhere on the vertical line - regardless of the distance to the target.

    So if you accept what I am saying, then the question becomes - do all you expert marksmen out there consider this factor? Do you test for misalignment when you first mount your scope? If you perform a test like I described, will not the majority of us all find misalignment problems which actually are significant - or is the quality of the machining so good that we can normally safely ignore this error? If you do have an error and realise you need to fix it - what's the best way to go about this?

    Thanks!
     
  15. Ballisticboy

    Ballisticboy Active Member

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    You are assuming the pellet travells in a straight horrizontal line which it doesn't. Spin Drift
     
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  16. C.Eaton

    C.Eaton Confirmed Anschutz Nut...

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    I was going to say that after all your posts we are dealing with something that zig-zags all over the shop down range.
    I also wouldn't really recommend adjustable mounts as they tend to open up a whole new set of variables with the key word being 'adjustable'.
    Just get a quality set of mounts, accept that perfection is unattainable and learn the quirks of your particular rifle/pellet...;)
     
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  17. athelas

    athelas New Member

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    I think you might be right !! :) Thanks!
     
  18. athelas

    athelas New Member

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    Thanks for enlightening me about this. It is a new one to me :)
     
  19. Phil Kennett

    Phil Kennett Active Member

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    May I ask what do people use to shim a correct mis-alignment
     
  20. C.Eaton

    C.Eaton Confirmed Anschutz Nut...

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    Back in the nineties I used to do this:
    Fixt the rifle in a workmate so it can't move, fire three shots into a card 25-30 yds away then carefully remove and optically centre the scope.
    Then wrapping the scope in clingfilm on the tube I'd put it back in the mounts but squeezed onto P60 car repair paste in the bottom of the mounts.
    The idea is to line the scope up with the holes you shot earlier so guaranteeing that the scope and barrel are in perfect alignment.
    It's messy but effective.
    These days I just stick the scope on, zero it and shoot it, it's an age thing...;)
     
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