Vortex Optics VIPER PST 6-24X50 RIFLESCOPE - Manual (Page 3)

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RIFLESCO PE
MOA Subtensions
The EBR-1 reticle is based on minute-of-angle (MOA) subtensions.
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. EBR-1 MOA Reticle Subtensions
In the Viper PST second focal plane
riflescopes, the listed MOA subtensions
of the EBR-1 reticle are only valid at
the highest magnifications of the scope.
However, by understanding the relationship
of magnification and subtensions,
ranging, holdovers, and wind drift can still be calculated at partial
magnifications. Here are some examples:
• If the magnification is set at ½ the full magnification, subtension
values will be two times the spec listed in the manual.
• If the magnification is set at 1/3 the full magnification, subtension
values will be three times the spec listed in the manual.
• If the magnification is set at ¼ the full magnification, subtension
values will be four times the spec listed in the manual.
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
five percent error in ranging
and holdover adjustments.
This will result in missed
shots at longer distances.
Estimating MOA
Heavy crosshair
subtends 1 MOA
Fine crosshair
subtends .06 MOA
Gap subtends
1MOA 2.5 MOA 1 MOA
6–24x50 Reticle Subtensions
(Valid at 24x)
R iflescope
M agnification
24x
12x
8x
6x 1 MOA
2 MOA
3 MOA
4 MOA
a ctual s ubtension of
1 Moa R eticle s pace
Subtension Changes with Magnification