Range estimation with mil reticles Milliradian

p4l mil reticle used in schmidt & bender 5-25x56 pm ii lp scope sight seen @ 25x magnification.



premade table range estimation showing target sizes, distances , corresponding angular measurments. angular sizes given in milliradians, ranges in meters, , target sizes shown in both in centimeters, millimeters , inches.

many telescopic sights used on rifles have reticles marked in mils. can either accomplished lines or dots, , latter called mil-dots. mil reticle serves 2 purposes, range estimation , trajectory correction.

with mil reticle-equipped scope distance object can estimated fair degree of accuracy trained user determining how many angular mils object of known size subtends. once distance known, drop of bullet @ range (see external ballistics), converted angular mils, can used adjust aiming point. mil-reticle scopes have both horizontal , vertical crosshairs marked; horizontal , vertical marks used range estimation , vertical marks bullet drop compensation. trained users, however, can use horizontal dots compensate bullet drift due wind. mil-reticle-equipped scopes suited long shots under uncertain conditions, such encountered military , law enforcement snipers, varmint hunters , other field shooters. these riflemen must able aim @ varying targets @ unknown (sometimes long) distances, accurate compensation bullet drop required.

mildot chart used snipers.

angle can used either calculating target size or range if 1 of them known. range known angle give size, size known range given. when out in field angle can measured approximately using calibrated optics or using 1 s fingers , hands. outstretched arm 1 finger approximately 30 mils wide, fist 150 mils , spread hand 300 mils.

mil reticles have dots or marks spacing of 1 mil in between, graduations can finer , coarser (i.e. 0.8 or 1.2 mil).

units target size , range

while radian defined angle on unit circle arc , radius have equal length, milliradian defined angle arc length 1 thousandth of radius. therefore, when using milliradians range estimation, unit used target distance needs thousand times large unit used target size. metric units particularly useful in conjunction mil reticle because mental arithmetic simpler decimal units, thereby requiring less mental calculation in field. using range estimation formula units meters range , millimeters target size matter of moving decimals , division, without need of multiplication additional constants, producing fewer rounding errors.

distance in meters

=


target in millimeters
angle in mils




{\displaystyle {\text{distance in meters}}={\frac {\text{target in millimeters}}{\text{angle in mils}}}}

the same holds true calculating target distance in kilometers using target size in meters.

distance in kilometers

=


target in meters
angle in mils




{\displaystyle {\text{distance in kilometers}}={\frac {\text{target in meters}}{\text{angle in mils}}}}

also, in general same unit can used subtension , range if multiplied factor of thousand, i.e.

distance in meters

=


target in meters
angle in mils


×
1
,
000


{\displaystyle {\text{distance in meters}}={\frac {\text{target in meters}}{\text{angle in mils}}}\times 1,000}

if using imperial units yards distance , inches target size, 1 has multiply factor of  ⁄36 ≈ 27.78, since there 36 inches in 1 yard.

distance in yards

=


target in inches
angle in mils


×
27.78


{\displaystyle {\text{distance in yards}}={\frac {\text{target in inches}}{\text{angle in mils}}}\times 27.78}

if using metric unit meters distance , imperial unit inches target size, 1 has multiply factor of 25.4, since 1 inch defined 25.4 millimeters.

distance in meters

=


target in inches
angle in mils


×
25.4


{\displaystyle {\text{distance in meters}}={\frac {\text{target in inches}}{\text{angle in mils}}}\times 25.4}



practical examples

estimating range using hands on extended arm reference angular size in mils.

land rovers 3 4 m long, smaller tank or apc/micv @ 6 m (e.g. t-34 or bmp) , 10 m big tank. front land rover 1.5 m wide, tanks around 3 - 3.5 m. swb land rover side 1 finger wide @ 100 m. modern tank have @ bit on 300 m.

if instance target known 1.5 m in height (1500 mm) measured 2.8 mils in reticle, range can estimated to:

distance in meters

=



1500
 

mm



2.8
 

mils




=
535.7
 

m



{\displaystyle {\text{distance in meters}}={\frac {1500~{\text{mm}}}{2.8~{\text{mils}}}}=535.7~{\text{m}}}

so if above-mentioned 6 m long bmp (6000 mm) viewed @ 6 mils distance 1000 m, , if angle of view twice large (12 mils) distance half much, 500 m.

when used riflescopes of variable objective magnification , fixed reticle magnification (where reticle in second focal plane), formula can modified to:

distance in meters

=


size in mm
angle in mils


×


mag
10




{\displaystyle {\text{distance in meters}}={\frac {\text{size in mm}}{\text{angle in mils}}}\times {\frac {\text{mag}}{10}}}

where mag scope magnification. however, user should verify individual scope since not calibrated @ 10×. above target distance , target size can given in 2 units of length ratio of 1000:1.