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Question about Zeroing

  • 13-03-2020 5:18pm
    #1
    Registered Users Posts: 146 ✭✭ Bagpipe


    Hello,


    So i've zeroed my other rifle at 50 yards with 12x power on a Bushnell 6-18x50 using Fiocchi .223 ballistic tips. If i turn down the magnification or power to 6x or 3x does mean that the scope will no longer be accurate at 50 yards? (Changing through the different powers/magnifications doesnt affect the accuracy of the scope, the accuracy has only to do with how steady and level i can hold the rifle and ensuring that the shots are on a point?)



    So say I want to shoot at 200 yards using the 12x power, can i start by getting a tight group at 50 yards with 3x and then slowly work my way up to 200 yards at 6x or the 12x?



    If the above makes any sense at all, Im not very good with firearms terms yet:D



Comments

  • Registered Users Posts: 2,614 ✭✭✭ deerhunter1


    Bagpipe wrote: »
    Hello,


    So i've zeroed my other rifle at 50 yards with 12x power on a Bushnell 6-18x50 using Fiocchi .223 ballistic tips. If i turn down the magnification or power to 6x or 3x does mean that the scope will no longer be accurate at 50 yards? (Changing through the different powers/magnifications doesnt affect the accuracy of the scope, the accuracy has only to do with how steady and level i can hold the rifle and ensuring that the shots are on a point?)



    So say I want to shoot at 200 yards using the 12x power, can i start by getting a tight group at 50 yards with 3x and then slowly work my way up to 200 yards at 6x or the 12x?


    If the above makes any sense at all, Im not very good with firearms terms yet:D


    If you zeroed at 50 yards and you want to shoot at 200yards,you should be 1" or thereabouts low at 200 depending how flat the rifle shoots


  • Registered Users Posts: 146 ✭✭ Bagpipe


    If you zeroed at 50 yards and you want to shoot at 200yards,you should be 1" or thereabouts low at 200 depending how flat the rifle shoots




    Okay thank you for the reply.


    So lets say that I have zeroed at 200 yards at 12x power/magnification and if a target such as a fox appears at around 100 yards, would lowering the power/mag to 6x mean that the scope will still be zeroed at 200 yards?


  • Registered Users Posts: 2,614 ✭✭✭ deerhunter1


    Bagpipe wrote: »
    Okay thank you for the reply.


    So lets say that I have zeroed at 200 yards at 12x power/magnification and if a target such as a fox appears at around 100 yards, would lowering the power/mag to 6x mean that the scope will still be zeroed at 200 yards?

    correct,


  • Registered Users Posts: 146 ✭✭ Bagpipe


    correct,


    So then (if zeroed at 200 yards) to accurately shoot 100 yards I would shoot approx. 2" below the reticle center?


  • Registered Users Posts: 2,614 ✭✭✭ deerhunter1


    Bagpipe wrote: »
    So then (if zeroed at 200 yards) to accurately shoot 100 yards I would shoot approx. 2" below the reticle center?

    depends on the weight of bullet,at those distances should be no need to aim off if shooting foxes etc unless shooting targets in competitions,


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  • Registered Users Posts: 146 ✭✭ Bagpipe


    depends on the weight of bullet,at those distances should be no need to aim off if shooting foxes etc unless shooting targets in competitions,


    Ok thats perfect, thank you very much for the help!


  • Registered Users Posts: 2,614 ✭✭✭ deerhunter1


    Bagpipe wrote: »
    Ok thats perfect, thank you very much for the help!

    no problem


  • Moderators, Sports Moderators Posts: 27,534 Mod ✭✭✭✭ Cass


    If i'm understanding your question changing mag power on your scope should not cause a change in the point of impact. Cheaper scopes may cause this but its rare and as you said sometimes inaccuracy can be as a cause of the shooter using a lower power which allows for a much larger "variance" in your point of aim.

    As for actual zero. The yard stick of 1" high with a 100 yard zero (or 1" low with a 200 yard zero) can be effective, but only with a given range of ammo. Some ammo uses more adjustment/holdoff and others use less.

    For example a 53 to 55gr should work with the 1" holdover/under method above, but 40gr v-max is so fast and flat that there is almost not difference in zero between 100 and 200 yards. Well in my rifle there is little to no difference. If i use a 64gr to 75gr in my other rifle the drop between 100 and 200 yards can be as much as 2". So a 1" high hold with a 100 yard zero will give a good central point for both 100 and 200 yard shooting, but a zero for neither.

    Math is fun :D

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  • Registered Users Posts: 194 ✭✭ keith s


    Zooming in and out should only affect the hold over (when using mil dot for example) on a second focal plane scope.

    Once zeroed at a certain distance, then the crosshair POA (point of aim) should always be correct (match the point of impact) at the distance it's zeroed for.

    If you think the scope is not working correctly, stick it in a good bench rest vice or something that will not move. Point it at a target at your zeroed distance and zoom in and out.

    On a second focal plane scope you will see the mil dots changes the POA but the crosshair should remain on point.

    With the above test, the rifle has not moved so (in theory) its going to impact the same point all the time and you can compare the crosshairs POA at the different zoom power.


  • Registered Users Posts: 146 ✭✭ Bagpipe


    Cass wrote: »
    If i'm understanding your question changing mag power on your scope should not cause a change in the point of impact. Cheaper scopes may cause this but its rare and as you said sometimes inaccuracy can be as a cause of the shooter using a lower power which allows for a much larger "variance" in your point of aim.

    As for actual zero. The yard stick of 1" high with a 100 yard zero (or 1" low with a 200 yard zero) can be effective, but only with a given range of ammo. Some ammo uses more adjustment/holdoff and others use less.

    For example a 53 to 55gr should work with the 1" holdover/under method above, but 40gr v-max is so fast and flat that there is almost not difference in zero between 100 and 200 yards. Well in my rifle there is little to no difference. If i use a 64gr to 75gr in my other rifle the drop between 100 and 200 yards can be as much as 2". So a 1" high hold with a 100 yard zero will give a good central point for both 100 and 200 yard shooting, but a zero for neither.

    Math is fun :D
    keith s wrote: »
    Zooming in and out should only affect the hold over (when using mil dot for example) on a second focal plane scope.

    Once zeroed at a certain distance, then the crosshair POA (point of aim) should always be correct (match the point of impact) at the distance it's zeroed for.

    If you think the scope is not working correctly, stick it in a good bench rest vice or something that will not move. Point it at a target at your zeroed distance and zoom in and out.

    On a second focal plane scope you will see the mil dots changes the POA but the crosshair should remain on point.

    With the above test, the rifle has not moved so (in theory) its going to impact the same point all the time and you can compare the crosshairs POA at the different zoom power.


    Thats brilliant, thank you very much for the help guys!


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  • Registered Users Posts: 194 ✭✭ keith s


    No worries,

    I think it's the hold over (mil-dot and the likes) that catch people out sometimes.

    As an example: If you had zeroed at 50mtr and at minimum zoom/power, the 2nd mil dot down just happens to be bang on at 100mtr, then you can use the the 2nd mil-dot for your 100mtr #as long as you stay on minimum power#.

    If you adjust the power, then the 2nd mil-dot down will no longer hit the 100 bang on (with 2nd focal pane scopes).

    A 1st focal plane scope on the other hand will / should allow you to use the mil-dots at any power, as the crosshair will adjust in size as you zoom in and out.

    The down side to a 1st focal plane scope can be that the crosshair can sometimes get so big, that it will block out the target, especially if your shooting at paper and the target is a small bullseye.

    Hope that makes sense.


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