The Overwatch
Formulas
Distance
Milliradian-based Reticles
YARDS
Target Size (Inches) x 27.77 ÷ Target Size (Mils) = Distance (Yards)
​​​
10 (Inches) x 27.77 ÷ .2 (Mils) = 1,388 Yards
10 x 27.77 ÷ .2 = 1,388 Yards
​
Target Size (Yards) x 1000 ÷ Target Size (Mils) = Distance to Target (Yards)
2 (Yards) x 1000 ÷ .25 (Mils) = 800 Yards
2 x 1000 ÷ .25 = 800 Yards
​
METERS
​
Target Size (cm) x 10 ÷ Target Size (Mils) = Distance (Meters)
25.4 (cm) x 10 ÷ .5 (Mils) = 508 Meters
​
25.4 x 10 ÷ .5 = 508 Meters
Target Size (Inches) x 25.4 ÷ Target Size (Mils) = Distance to Target (Meters)
10 (Inches) x 25.4 ÷ .25 (Mils) = 1,016 Meters
10 x 25.4 ÷ .25 = 1,016 Meters
Target Size (Meters) x 1000 ÷ Target Size (Mils) = Distance to Target (Meters)
2 (Meters) x 1000 ÷ 2.8 (Mils) = 714 Meters
2 x 1000 ÷ 2.8 = 714 Meters
Minute of Angle-based Reticles
​
YARDS
​
Target Size (Inches) x 95.5 ÷ Target Size (MOA) = Distance to Target (Yards)
10 (Inches) x 95.5 ÷ 1.25 (MOA) = 764 Yards
10 x 95.5 ÷ 1.25 = 764 Yards
​
METERS
Target Size (Inches) x 87.3 ÷ Target Size (MOA) = Distance to Target (Meters)
72 (Inches) x 87.3 ÷ 5.5 (MOA) = 1,142 Meters
72 x 87.3 ÷ 5.5 = 1,142 Meters
Target Size (Meters) x 3438 ÷ Target Size (MOA) = Distance to Target (Meters)
​
Target Size (cm) x 34.38 ÷ Target Size (MOA) = Distance to Target (Meters)
Meters to Yards - Yards to Meters
Conversion
Meters to Yards
Multiply by 1.0936
Ex. 500 Meters x 1.0936 = 547 Yards
Yards to Meters
Divide by 1.0936
Ex. 900 Yards ÷ 1.0936 = 823 Meters
MOA to MILS - MILS to MOA
MOA to MILS
Divide by 3.5
Ex. 5 MOA ÷ 3.5 = 1.42 MILS
MILS to MOA
Multiply by 3.5
Ex. 2.6 MILS x 3.5 = 9.1 MOA
QUICK WIND/B.C. METHOD
(This is the best and fastest way to read the wind)
Wind Speed / Gun Number x 1/1000 Distance x Cosine Angle
12 / 4 x .4 x .5 = .6 Mils
​
Wind - 12 mph from 1 o’clock
Distance - 400 yards
Count by 4 up to 12 or divide 12 by 4 = 3
3 x 4 (4 because we are at 400 yards) = 1.2 Mils
1.2 Mils is my full-value wind hold.
Now I need to adjust for the wind angle.
The cosine for 1 o'clock is .50. You can think of this in a few different ways and pick what is easiest for you.
1.2 x .50 = .6 Mils
12/2 = .6 Mils
50% of 12 = .6 Mils
​
FOR MORE INFORMATION ON QUICK WIND SEE QUICK WIND IN MY BLOG
​
Tactical Loophole Shooting
BH x C / distance to loophole = mils - DOPE
BH - Bore Hight in Inches
C - BH in Mils C = BH x 25.4
Distance to loophole in feet
1.75 x 45 / 12 = 6.56 mils - dope
Next, subtract your Dope from 6.56
at 500 yards, my Dope is 2.8 mils
6.56 - 2.8 = 3.76 mils
Our bullet will clear the loophole if we have 3.76 mils of clearance.
This formula will work with 99% of rifles
BH x 80 / distance to loophole - Dope
WINDROSE
Cosine Angle Calculator
1/4 Windrose
Multiply the wind speed or Mil hold by the cosine for th e wind angle.
Full Windrose
EX: 12 MPH x .707 (45°) = 8.454 MPH
​
EX: 1.2 (Mil hold) x .707 (45°) = .85 Mils
Spin Drift
Drift - Spin drift in inches, in the direction of rifling twist
SG - The gyroscopic stability factor
TOF - The bullets time of fight
Drift = 1.25 x (SG + 1.2) x TOF ^ 1.83.
Ex.
SG - 1.83
TOF - .7 @ 500 Yards
1.25 (1.83 + 1.2).7^1.83 = 1.97 Inches
TOF @ 1000 = 1.75
1.25 x (1.83 + 1.2) x 1.75^1.83 = 10.54 Inches
Coriolis Effect
F = 2 * m * v * ω * sin(α)
F - is the Coriolis force.
m - is the mass of the moving object.
v - is the velocity of the moving object.
ω - is the angular velocity of the Earth.
α - is the latitude at which the object is located.
ω = 2π/24h ≈ 0.0000727 1/s (2π means 360°
Eötvös Effect
1+2*Ω*MV/-32.2*cos(Rads(Lat))*sin(Rads(Azimuth))
Magnus Effect
Fm = S (w × v)
Fm = Magnus force vector
w = Angular velocity vector of the object
v = Velocity of the object
S = Air resistance coefficient across the surface of the object
Angle of Fire
Distance * (Cos = Corrected Distance
Ex. 500 yds at a 25° angle
500 * .940 = 470 yds