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Yep. Another annoying MOA question

Discussion in 'Long Gun Accessories and Optics' started by Triggs, Jul 5, 2017.

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  1. Triggs

    Triggs Member

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    Is it safe to say when figuring MOA that you just take your known bullet drop and divide by distance? For example, hit a hog at about 285 today. I know my 6.5 creedmoor 129 superperfmance round drops approximately 7 in at 300. So i went up 2 moa +1 for 9 clicks and drilled it. I understand there are other factors but will this formula work for a general rule?
     
  2. Varminterror

    Varminterror Member

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    Um... I'm not sure I'm tracking your statement, but I'll give it a run...

    1MOA = ~1" / 100yrds. So If you're looking for a ratio, you can consider it this way: (Real range) * 1"/100yrds = inches/ 1MOA at that range. Since you know your drop, you can divide by that expression to convert your inches of drop to MOA --> 7" / (300yrds * 1" / 100yrds) --> Simplifying that, you can simply "drop the zeros in your range" to get a much simpler expression 7 / 3 = 2.333 MOA, which is 9 clicks in a 1/4 MOA per click or 1/4 IPHY per click optic.

    That's not a rule of thumb, that's just a combination of a simple unit conversion and a simple ratio expression... The only "rule of thumb" involved there is the use of ~1" at 100yrds = 1MOA, when in reality, 1MOA dispersion on a normal target face at 100yrds is 1.047197559...". For most shooters, that ~4.7% deviation doesn't matter much, so it's neglected - much like how you were able to neglect your difference between 285yrds and 300yrds, and between 2.333MOA and 2.25MOA... One of those aspects slid you one direction, the other slid you back the other way, and the impact was on target.
     
  3. MCMXI
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    MCMXI Contributing Member

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    Good explanation!
     
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  4. Triggs

    Triggs Member

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    So it sounds as though i am on the right track correct? So using this information if i know im dropping 40 inches at 500 and I know 1 MOA at this distance is approximately 5" I would adjust 8 MOA correct?

    I know this gets posted alot I am sure, but do appreciate the help. I am using a vortex viper 6.5 x 20 x 50 with 1/4 MOA zero is 100
     
  5. Varminterror

    Varminterror Member

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    Yup - 40" at 500 = ~ 8MOA. Good enough for MOST shots.
     
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  6. Triggs

    Triggs Member

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    Thanks for hour time.
     
  7. Varminterror

    Varminterror Member

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    If you want more detail - there's detail to be had, but for most shooters, the above will have you in the hunt - within 1 click of the true value. If you get your post count up so you can PM, I can shoot you a little more info on the difference between what some folks call "Shooter's MOA" - which is what you're using here, aka "IPHY" Inch Per Hundred Yards, and true MOA. Your 8MOA estimate above ends up being within 1.9" at 500yrds, which seems like a lot, but it's really only 1 click difference, as 2 clicks goes as far past the true value as 1 click is short from it.
     
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  8. Triggs

    Triggs Member

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    My post count? I just joined so I'm taking that i need more posts to do PMs
     
  9. Varminterror

    Varminterror Member

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    Ya know - I've always assumed you need a certain minumum here - I have 10 minimum in my head, but now that you ask, I'm not sure....

    But yeah, if you want more detail on MOA, IPHY, MRAD, etc, and ballistic formulii in the future, shoot me a PM.
     
  10. Triggs

    Triggs Member

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    Will do sir. I broke the calculator out on one I range at 450 and and used 1.047 and was of course low one way high another. So waited for it to stand and nailed it. Furthest hog I have shot yet. Thank God for the dead wind bc i have not a clue on that yet
     
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  11. dc.fireman

    dc.fireman Member

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    windeffect.jpg

    Very basic, but very accurate.
     
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  12. Varminterror

    Varminterror Member

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    C'mon @dc.fireman, if you're going to drop a spin drift/magnus diagram on some new guys, you gotta take the time to elaborate a bit so it can blow minds in amazement instead of confusion.
     
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  13. LoonWulf
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    LoonWulf Contributing Member

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    .....well he got an Oooooo PRETTY! from me.
     
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  14. Klint Beastwood

    Klint Beastwood member

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    stuff
     

    Attached Files:

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  15. Varminterror

    Varminterror Member

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    [​IMG]

    This one is a bit off - it's confusing IPHY and MOA in the top left.

    1MOA at 100yrds is 2.7cm, at 400, it's 10.6cm. Most folks don't shoot well enough to tell a quarter or half centimeter difference, but that chart is in IPHY, not MOA.
     
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  16. Klint Beastwood

    Klint Beastwood member

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    Yes sir, you are right. I was going to look through my google drive for some other ones....but that will take awhile and im lazy unless someone specifically wanted me too.

    Like you said most people dont use the .047 with true MOA so I my thought was to share if anyone reading wanted a quick printable reference sheet. I have IPHY and true MOA somewhere but...I'm more of a MIL guy myself so I'd have to cipher though a couple hundred pages of that.
     
    Last edited: Aug 3, 2017
  17. dc.fireman

    dc.fireman Member

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    lol.
    I prefer to let it ruminate for awhile, so as not to take the joy of discovery away from someone. My apologies, for resurrecting a dying thread, but I had to lol at your comment anyhow...
     
  18. JeffG

    JeffG Member

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    ROFL!!:rofl:
     
  19. Varminterror

    Varminterror Member

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    I shot an all prone "shoot for your life" match yesterday morning, and the application of @dc.fireman's graphic was a pretty hot topic. Wind wasn't awful, but it was pretty close to it. Switching from 10 to 1, climbing and falling back and forth between 1-3 up to 20 standing with 25-30 gusts... Between flights, so many of us were debating whether to take off a tenth or not, and I heard a couple guys mention they FORGOT to put a couple tenths back on when the wind died down, cost them a few points, sounded like one guy even fell out because of it. I added mine to bring me up, because I was only driving 2580fps and dang sure didn't want to slip off of the bottom of the plate.
     
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  20. cactus02

    cactus02 Member

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    One of the best ways to figure bullet drop and moa is to go to Hornady or Federal ballistic programs and get the figures to plug into the formula. Get the printout in 25 yard increments and print it up. With care you should be able to hit out to 500 depending on bullet. (don't ask a 40 grain bullet in wind to go 500.)
     
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