Vortex Optics RAZOR HD 5-20X50 RIFLESCOPE — First Focal Plane User Manual
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MOA Subtensions
The EBR-1 reticle is based on minute-of-angle (MOA)
subtensions. Many shooters
are very familiar with the
MOA system used in hunting
riflescopes. MOA measurements
are based on degrees and
minutes: 360 degrees in a
circle, 60 minutes in a degree
for a total of 21,600 minutes.
These angular measurements
are used to estimate range and
correct for bullet trajectory
drop in riflescopes. 1 MOA will
correspond to 1.05 inches at a 100
yard distance, 2.1 inches at 200
yards, 3.15 inches at 300 yards,
and so on.
When used in a first focal plane
riflescope, such as the Vortex Razor HD riflescopes,
the MOA subtensions of the EBR-1 reticle are valid at all
magnification levels. This means the shooter can use the
magnification level most appropriate for the situation and
still have effective holdover and windage reference marks.
This is extremely valuable in a high-stress situation because
Although 1 MOA is very
commonly corresponded
to 1 inch at 100 yards,
this is not quite correct
1 MOA at 100 yards
equals 1.05 inches.
Calling 1 MOA an inch
per 100 yards may be
acceptable at shorter
distances, but it will
cause a fi ve percent error
in ranging and holdover
adjustments. This will
result in missed shots at
longer distances.
Estimating MOA
5 MOA subtension marks
2 MOA subtension marks
EBR-1 Reticle Subtensions
Fine: .2 MOA
Heavy: 5 MOA
Crosshair thickness
the shooter does not have to remember to set the scope to
one particular magnification to get valid holdovers—an
action necessary in the more common second focal plane
reticles.
Heavy Crosshair
Fine Crosshair