MOA formula?'s

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by darrindlh, Oct 8, 2011.

  1. darrindlh

    darrindlh Well-Known Member

    Messages:
    400
    Joined:
    Apr 24, 2009
    I am trying to explain this so please bare with me. So I am trying to verify my drop charts, if I impact different than my drop chart says, what is the formula to find out the moa correction at any distance other than 100 yrds.

    Darrin
     
  2. Edd

    Edd Well-Known Member

    Messages:
    2,388
    Joined:
    Jan 26, 2011
    If I correctly understand what you are wanting to do, it would be the measurement in inches on the target divided by the distance in yards multiplied by 100.

    Example: If you were off 2.25 inches at 300 yards.
    2.25 ÷ 300 x 100 = .75 moa
     

  3. LouBoyd

    LouBoyd Well-Known Member

    Messages:
    770
    Joined:
    Oct 15, 2007
    1 MOA is not 1 inch at 100 yards. It is 1.047 inches. That's a 4.7% error.
    In Edd's calculation above the answer is not .75 MOA It should be .716 MOA. Does that matter to your shooting? Only you can decide that.

    Actually the number is not 1.047 but that has less than a 0.02% error. The correct number is irrational and cannot be written as an exact decimal number. Would you use 3 for PI instead of 3.14 or 3.1416 or 3.14159?
     
  4. Edd

    Edd Well-Known Member

    Messages:
    2,388
    Joined:
    Jan 26, 2011
    I knew that was coming as I was typing.

    If being off by slightly less than a half inch at 1000 yards is going to cause a problem, all you have to do is add another step.

    Example:
    You are off 10 inches at 1000 yards.
    10 ÷ 1.047 ÷ 1000 x 100 = .955 moa
     
  5. darrindlh

    darrindlh Well-Known Member

    Messages:
    400
    Joined:
    Apr 24, 2009
    So if I understand this correctly If I am off 6 inches at 400 yrds then

    6/ 1.047/ 400*100= 1.43 moa

    Right after I rounded the decimal\

    Darrin
     
  6. LouBoyd

    LouBoyd Well-Known Member

    Messages:
    770
    Joined:
    Oct 15, 2007
    Your right, that's no big deal if you're doing a second shot correction on a 10 inch miss.
    On the other hand if you're shooting at 1000 yards and cllick up 22 MOA thinking you're getting 220 inches from a 100 yard zero your shot will be about 10 inches high. That may be why "you are off by 10" at 1000 yards" with your first shot. And when hunting how do you see the impact at that distance to know how far you were off?

    If you can see bullet impacts why do any calculations? Just walk your shots onto the target. ;-)
     
    Last edited: Oct 8, 2011
  7. Edd

    Edd Well-Known Member

    Messages:
    2,388
    Joined:
    Jan 26, 2011
    That is correct. There are other ways to way to calculate it but they don't show the trail of how you got the value. Here is a shorter method.

    95.5 x inches ÷ yards = moa
     
  8. darrindlh

    darrindlh Well-Known Member

    Messages:
    400
    Joined:
    Apr 24, 2009
    You are exactly right. In a hunting situation I will no be doing calculations. mainly I wanted it for the range. and for verifying my drop charts. You guys are awesome and I thank you for your patience with me while I am learning.

    Darrin
     
  9. cummin_un_glued

    cummin_un_glued Well-Known Member

    Messages:
    396
    Joined:
    Nov 27, 2010
    ok i'm no expert by any stretch but whats the reason for a correction? if the impact dosnt match the ballistic chart then how will a correction factor fix that? wouldnt the factor be different for every different shot distance? i just had the same problem this week shooting at 775 yards, chart show's 15.1 moa and impact required 17 moa. done some digging and found my muzzle volicity was off 125fps. fixed that and now the chart shows 16.9 moa for 775 yards. just food for thought is all.
     
  10. darrindlh

    darrindlh Well-Known Member

    Messages:
    400
    Joined:
    Apr 24, 2009
    The reason for he correction is my ballistic program I am using has a validation trajectory tool on it. So while at the range I need to know the correction if my bullet does not hit the point of impact with the given moa adjustment to be able to verify and have correct drop chart for my rifle.

    With the validation tool it will correct my velocity with the adjusted moa correction I made at the range.

    Darrin
     
  11. Pons

    Pons Well-Known Member

    Messages:
    124
    Joined:
    Mar 13, 2011
    Did you calibrate the adjustments on your scope to moa results at fixed distance? (they aren't all perfect) Just did one the other day, came up with around .94 moa per four clicks, but was very close to .99 inch at 100 yds per 4 clicks.
     
    Last edited: Oct 8, 2011
  12. darrindlh

    darrindlh Well-Known Member

    Messages:
    400
    Joined:
    Apr 24, 2009
    Yeah I did. My scope turrets are moa.

    Darrin