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Bubble level??

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  #43  
Unread 03-28-2013, 03:02 PM
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Re: Bubble level??

I wish I could remember where I came across that. It's been so long I wouldn't doubt i've forgotten more about the article than what I put here... more questions than answers it seems


t
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  •   #44  
    Unread 03-28-2013, 06:36 PM
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    Join Date: Oct 2007
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    Re: Bubble level??

    That picture is a great example why the SCOPE has to be perfectly level. The conversation Mark and I were having has to do with the GUN not being perfectly square under an (already leveled scope).

    Lets assume a 308 shooting a Berger 168gn vld at 2650fps. (just guessing)
    Actual bullet drop at 600 yards would be about 60"

    The 60" would represent the Radius of our imaginary circle. The circumference would be about 377", each degree would represent 1.047". The measure arc of a 10* cant would cause a miss of about 10".

    The picture Outlaw posted appears to be at about 5* cant per line not 10*. Which would put the groups about 5" left, and 5" right of the ceterline. I can't tell what size dot they were using so it makes it difficult to confirm how far from center the impacts were.

    I wanted to make sure the readers were not confused about the difference between a scope being level, vs having to get the bore in line with the scope.

    Joel
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      #45  
    Unread 03-28-2013, 08:20 PM
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    Re: Bubble level??

    Quote:
    Originally Posted by aroshtr View Post
    That picture is a great example why the SCOPE has to be perfectly level. The conversation Mark and I were having has to do with the GUN not being perfectly square under an (already leveled scope).

    Lets assume a 308 shooting a Berger 168gn vld at 2650fps. (just guessing)
    Actual bullet drop at 600 yards would be about 60"

    The 60" would represent the Radius of our imaginary circle. The circumference would be about 377", each degree would represent 1.047". The measure arc of a 10* cant would cause a miss of about 10".

    The picture Outlaw posted appears to be at about 5* cant per line not 10*. Which would put the groups about 5" left, and 5" right of the ceterline. I can't tell what size dot they were using so it makes it difficult to confirm how far from center the impacts were.

    I wanted to make sure the readers were not confused about the difference between a scope being level, vs having to get the bore in line with the scope.

    Joel
    Joel, I agree these are two different examples but I don't believe the effect is going to be a lot different.

    If we take a bullet that drops say 2" in a hundred yards and we ad anothe 1.8" for scope height to it we have a muzzle to line of sight convergence or 3.8" @ 100 yds. If we went to extreme and canted the rifle and scope 90*, the bullet would impact 3.8" offset of center. Multiply that by 6 and we get 22.8" @ 600 yds. A slight cant of 5-10* will be a small fraction of that.

    Do you have a math model that can predict the offset?
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