want to convert 1/8 MoA At 100 yards to mm

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want to convert 1/8 MoA At 100 yards to mm

Postby sesse » Wed Jul 28, 2004 12:54 pm

hi !
please help me to convert 1/8 MoA to mm at 100 Yards ! i live in sweden and im thinking of bying a american riflescope ! Thanx
sesse
 

Re: want to convert 1/8 MoA At 100 yards to mm

Postby Knight » Thu Jul 29, 2004 1:07 am

sesse wrote:hi !
please help me to convert 1/8 MoA to mm at 100 Yards ! i live in sweden and im thinking of bying a american riflescope ! Thanx

Considering that you're looking for your answer in mm, I'm going to do the work completely in metric, as it will be easier to convert 100 yards to 91.44 meters up front than to convert yards to feet to inches and then convert them to mm.

That said, lets begin...

The angle of an arc is expressed in number of degrees. There are 360 degrees of arc to a full circle. Each degree consists of 60 minutes of arc. The distance covered by the measure of arc is relative to the circumference (total distance around the circle) it is contained within. Knowing the radius (distance to center of circle) circumference is easily calculated by using the constant pi . The ratio (represented by pi ) of circumference is constant to diameter (radius x 2) regardless of circle size.

Therefore, the circumferance at 91.44 meters is:

91.44 · 2 · 3.1416 = 574.54 m

That means that one degree of arc is:

574.54 / 360 = 1.596 m

and therefore one minute of arc is

1.596 m / 60 = 2.66e-2 m

and:

2.66e-2 m x 1000 mm/m = 26.6 mm per minute of Arc (MoA).

As the scope your looking at uses 1/8 MoA per click then:

26.6 mm / 8 = 3.32 mm

So, 1/8 MoA is equal to 3.32 mm @ 91.44 m (100 Yards)
William J. Knight
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Los Alamos National Labs
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