Vortex Optics VIPER HS 4-16X44 LR RIFLESCOPE - Manual (Page 5)

BDC dead-hold dead-hold
9 8
The Dead-Hold BDC reticle incorporates methods for wind drift correction
and range estimation using the hashmarks on the horizontal crosshair.
As in using the holdover hashmarks, the magnification must be set at the
highest magnification (18x for a 6–24x50 model).
Correcting for wind drift is done with the
hashmarks on the horizontal crosshair.
These hashmarks are spaced at 2 MOA,
with the inside ends of the heavy
horizontal crosshairs at 8 MOA from
center. Shooters familiar with the wind
drift numbers of particular ammunition
can use the hashmark spacing to help
estimate proper windage hold-off once
the correct range and wind are known or estimated. Use the online Vortex
Long Range Ballistic Calculator (LRBC) to learn wind drift numbers for
your loads.
Ranging distances is done using the following simple formula:
Using the Reticle for Wind Drift Compensation and Ranging
T
ARGET
’
S
K
NOWN
W
IDTH OR
H
EIGHT IN
I
NCHES X
100
T ARGET ’ S W IDTH OR H EIGHT IN MOA S M EASURED ON R ETICLE
R ANGE IN
Y ARDS
=
A shooter can compare a target object of known dimension (at shooting
distance) to either the vertical or horizontal hashmark spacing and roughly
estimate the range. Remember, hashmarks on the vertical crosshair are
spaced at 1.5 MOA, 4.5 MOA and 7.5 MOA. The top of the bottom
vertical heavy crosshair is 11 MOA from center. Horizontal hashmarks are
spaced at 2 MOAs.
Example: Ranging a Coyote p g g y
In your home area, you know that a coyote runs about three feet (36 inches)
in length. While out hunting, you observe a coyote
and range him with your scope set at the highest
magnification (18x for a 6–24x50 model). You see
that the coyote’s body covers about the distance
from the center crosshair to the edge of the heavy
part of the horizontal crosshair (8 MOA). Using the
simple formula, you can estimate the coyotes distance at 450 yards.
450 Y ARDS =
36 I
NCHES X
100
8 MOA M EASURED ON R ETICLE
3600
8
=
Example: Ranging a Deer p g g
When spotting a distant buck while deer hunting, you turn your scope to
the highest magnification (18x for a 6–24x50 model)
and range him. While looking through the scope, you
see that the distance from the top of his back to the
bottom of his chest (usually about an 18-inch depth
on a mature buck) spans from the center crosshair to
the 2nd hashmark down (4.5 MOA) on the reticle.
Using the formula, you can then estimate the deer’s distance at 400 yards.
400 Y ARDS =
18 I NCHES X 100
4.5 MOA M EASURED ON R ETICLE
1800
4.5
=
This formula has been simplified slightly to allow faster calculations, and
yields distance estimates which are 5 percent greater than actual distance.
If you desire more precise estimates, use the following formula:
T ARGET ’ S K NOWN W IDTH OR H EIGHT IN I NCHES X 95.5
T ARGET ’ S W IDTH OR H EIGHT IN MOA S M EASURED ON R ETICLE
R ANGE IN Y ARDS =
manual_reticle_bdc-sfp-13a.indd 8-9 anual_reticle_bdc-sfp-13a.indd 8-9 8/7/2013 7:31:07 AM 8/7/2013 7:31:0