1 shooter's MOA = 1 inch per 100 yards of range 1 shooter's MOA = .278 mils 1 mil = 3.6 shooter's MOA
MOA adjustment times the range in hundreds of yards (600 yards = 6) equals change of impact in inches. MOA X R = Inches
Inches adjustment divided by the range in hundreds of yards equals MOA. Inches ——— = MOA R
Desired MOA adjustment divided by the resolution of one click equals total adjustment in clicks. 5 MOA ————————————— = 20 clicks 1/4 (.25) minute clicks
I prefer to memorize my come-ups in clicks rather than MOA. Total drop in clicks from a 100 yard zero minus the total clicks of all come-ups to the new zero range equals your comeup to that range. Start at 200 yards and work out. Clicks at 500 yards minus come-ups to 200, 300, and 400 yards totaled equals come-up from 400 to 500 yards in clicks.
The height of an object in yards times 1,000 divided by the apparent height of the object in mils equals the range in yards. Height in meters yields range in meters. Height X 1000 —————— = Range mils
The apparent angle from vertical of mirage divided by 8 equals the windspeed in miles per hour. Mirage angle must be read with the wind blowing directly from the right or left. Turn your spotting scope if you have to. Angle
——— = MPH 8
The apparent angle from vertical of smoke, flags, or the arm pointing at lightly balled piece of paper dropped from the shoulder divided by 4 equals the windspeed in miles per hour. Angle ——— = MPH 4
The Marine Corps Windage formula: Range in 100s of yards (600 yards = 6) times the wind in miles per hour divided by the constant C equals MOA change. Range X MPH —————— = MOA C For the M118 round at sea level C = 15 for 100 to 500 yards C = 14 for 600 yards C = 13 for 700 to 800 yards C = 12 for 900 yards C = 11 for 1000 yards For the M852 round at sea level C = 13 for 100 to 200 yards C = 12 for 300 to 400 yards C = 11 for 500 to 600 yards C = 10 for 700 to 900 yards C = 9 for 1000 yards
To adjust wind speed for differences in wind direction from ninety degrees from sightline multiply total wind speed by the constant C. MPH X C = adjusted MPH If wind direction is 90 degrees from sightline C = 1.0 If wind direction is 65 degrees from sightline C = .9 If wind direction is 45 degrees from sightline C = .75
If wind direction is 30 degrees from sightline C = .5 If wind direction is 15 degrees from sightline C = .25 If wind direction is 0 degrees from sightline C = 0
To adjust range for an up or down angle shot multiply the actual range by the Constant C. Range X C = adjusted range For an up or down slope of 5 degrees from horizontal C = .99 For an up or down slope of 10 degrees from horizontal C = .98 For an up or down slope of 15 degrees from horizontal C = .96 For an up or down slope of 20 degrees from horizontal C = .94 For an up or down slope of 25 degrees from horizontal C = .91 For an up or down slope of 30 degrees from horizontal C = .87 For an up or down slope of 35 degrees from horizontal C = .82 For an up or down slope of 40 degrees from horizontal C = .77 For an up or down slope of 45 degrees from horizontal C = .70 For an up or down slope of 50 degrees from horizontal C = .64 For an up or down slope of 55 degrees from horizontal C = .57 For an up or down slope of 60 degrees from horizontal C = .50 For an up or down slope of 65 degrees from horizontal C = .42 For an up or down slope of 70 degrees from horizontal C = .34 For an up or down slope of 75 degrees from horizontal C = .26 For an up or down slope of 80 degrees from horizontal C = .17 For an up or down slope of 85 degrees from horizontal C = .09 For an up or down slope of 90 degrees from horizontal C = 0
To adjust elevation for an up or down angle shot multiply your total drop from the horizontal boreline by the constant C and hold low by that amount from your estimated zero. Drop X C = hold UNDER For an up or down slope of 5 degrees from horizontal C = .004 For an up or down slope of 10 degrees from horizontal C = .015 For an up or down slope of 15 degrees from horizontal C = .034 For an up or down slope of 20 degrees from horizontal C = .060 For an up or down slope of 25 degrees from horizontal C = .094 For an up or down slope of 30 degrees from horizontal C = .134 For an up or down slope of 35 degrees from horizontal C = .181 For an up or down slope of 40 degrees from horizontal C = .235 For an up or down slope of 45 degrees from horizontal C = .293 For an up or down slope of 50 degrees from horizontal C = .357 For an up or down slope of 55 degrees from horizontal C = .426
For an up or down slope of 60 degrees from horizontal C = .500
Bullet time of flight times the speed of the target lateral to the sightline equals total lead. Speed in feet per second yields lead in feet. Time X Speed = Lead
Whenever I change ammunition, rifle, or altitude I work up a complete set of tables. A chronograph and a good ballistics program make this a whole lot easier. I record all my values in inches, MOA, and mils. For moving target leads I will also figure leads. I run all my charts from 100 to 1,000 yards in 100 yard increments. For noreflex hits I also run a set of charts from 25 to 200 yards in 25 yard increments. I record the total drop from the muzzle at each range. I also record the bullet time of flight. I figure my come-ups, and back calculate from the windage tables to get my constants for the Marine windage formula. With those two progressions memorized I can handle most of my shooting chores without my tables, if needs be.
For my elevation tables I record the drop in inches, MOA, and mils at each range for a zero at each range. That's one hundred sets of numbers for the long range charts. I only calculate my short range tables for a 100 yard zero. That's 8 sets of numbers. For my short range elevation charts I don't bother converting to mils. I also record my actual sight settings for each zero range.
My windage tables yield inches, MOA, and mils for each range and run from 5 to 30 miles per hour in 5 MPH increments.
My moving target chart is calculated for a walk (3 MPH), a trot (6 MPH), and a dash (10 MPH). I figure each range and speed (30 sets of numbers) in inches, MOA, mils and "leads." A lead is equal to the approximate width of a human body in profile– 12 inches. Leads are very easy to visualize. All moving target leads are figured from the center of the target.
I run my up/down slope adjustment charts from 5 degrees from horizontal to 60 degrees in 5 degree increments and list inches, MOA, and mils. Since this chart will not be used for quick targets-of-opportunity I calculate the hold under to be adjusted for, after the initial elevation adjustments have been made. Short range slope adjustment charts are critical for no-reflex shooting.
I also have charts listing the mil height and range for men 6 feet, 5 feet 9 inches, and 5 feet 6 inches tall as 6 feet
is unusually tall for most parts of the world. That's another reason I use yards instead of meters. A six foot (2 yards) man appears 2 mils tall at 1000 yards. The mil-dot formula is easy to calculate for two yards. A man would have to be 6 feet 6 inches tall to measure two meters. They're even rarer than six footers. To plug an average man into the mil-dot formula you'd have to use 1.77 meters. A little less handy than 2 yards. 6 feet = 2 yards 5 feet 9 inches = 1.9 yards 5 feet 6 inches = 1.8 yards
The SEALs found the following changes in elevation applied to their M852 rounds with changes in temperature. The higher the temperature, the higher the bullet impact. At 300 yards there is 1 MOA change in elevation per 20 degree change in temperature. At 600 yards there is 1 MOA change in elevation per 15 degree change in temperature. At 1000 yards there is 1 MOA change in elevation per 10 degree change in temperature.
Only by firing your rifle under field conditions can you determine how much effect temperature will have on your ammunition. If your computer generated charts don't match your field data you must go with the field data. Sometimes a change in ballistic coefficient will bring the computer in line with the real world.
The more of this information you memorize the better off you will be. Hosting by WebRing.
