- Pre-sighting
- You will save a significant amount of expense
and frustration by pre-sighting the scope
to the rifle before you take it out for zeroing.
Collimating, the most accurate and simple
technique for pre-sighting, is the system
most often used by gunsmiths. It can be done
quickly in the shop before leaving for the
range.
If a collimator is not available, you can
still do a good job of pre-sighting by a
method known as " bore-sighting".
At the range, set the scoped rifle up on
sandbags or other steady rest and place a
target at 100 yards. With the bolt removed,
look through the chamber and move around
the bore until you can see the bulls eye
centered in the bore.
Without moving the rifle from this position,
glance through the scope and note where the
reticle is positioned on the target. If the
scope reticle is not closely aligned to target
center, you need to adjust the base mounting
screws. Do not use the scope windage and
elevation adjustments for these pre-sighting
adjustments or you will run out of adjustment for final
zeroing.
All ABO (USA) serviced scopes are tested
to be certain that they provide maximum
internal
adjustment range. After testing, the reticle
is centered in the scope optically and
mechanically.
However, variations in rifle receiver dimension,
mounting holes drilled out of alignment
with
the receiver or barrels threaded into the
receiver at an angle will cause initial
scope
misalignment.
Therefore, it is important to make all major
bore sighting adjustments using the mount
adjustment screws. Make only final adjustments
using the scope's internal windage and elevation
screws. This will prevent running out of
internal adjustments.
- Note:
- There is no acceptable way to increase elevation
adjustments except to shim. Shim stock .010" thick,
placed under the rear of the mount base
will
raise the point of impact about 7".
To lower the point of impact, place the
shim
stock under the front end of the base.
- Zeroing a scope
- The range at which a scope should be zeroed
is a matter of personal judgment. If you
anticipate using the scope at distances of
100 yards or less, naturally a 100 yard zero
is appropriate. Mid-range trajectory would
be about 1" above the line of sight
and you could hold directly on target all
the way out to about 125 yards. If the anticipated
hunting distances are 200 yards or more,
you should zero your rifle at the longer
ranges. The MRT for a rifle zeroed at 200
yards is minimal for most cartridges (usually
about 1.5" to 2") and you can hold
directly on target for ranges out to slightly
more than 200 yards.
If a 200-yard range is not readily available,
you can obtain a satisfactory 200-yard zero
on a 100-yard range by zeroing about 1.5"
high.
A good rest, such as sandbags or steady rest
to reduce sighting errors, will help you
hold more steadily on target. Rest the forearm,
not the barrel, on the rest. If possible,
zero in a no-wind condition to establish
a standard zero. If you must zero in a wind,
make a note of the amount of drift attributable
to wind effect and when finally zeroed, make
a compensating adjustment to leave the scope
at standard (no-wind) zero. For example:
a 15MPH wind from the right at the 3 o'clock
position will normally drift a .30-06 factory
bullet about 1.5" to the left. When
you have finished zeroing in a 15MPH wind,
simply adjust the Windage knob 1.5"
to the left. This will result in standard
no-wind zero.
The first time about 25 yards out from the
muzzle. You can utilize this fact by firing
your first zero shot at 25 yards target.
If the first shot prints very close to the
center of the bulls eye at this range, you
can be confident that it will print on paper
at 100 yards. If there is a significant error
at 25 yards, make compensating changes to
bring the point of impact to zero. Since
the distance is only 1/4 of the 100 yard
final zero distance, you will need to make
4 times as much adjustment as you would at
100 yards.
For final zero, move the target to 100 yards
(assuming this to be the desired zero distance)
and fire at least 3 shots to establish a
pattern. Using the center of this group as
a reference, make any necessary adjustments
to move the point of impact to center. You
should fire another group of 3 shots to verify
that this adjustment was correct. Do not
trust a one-shot zero as accurate.
Note:
- For maximum precision, allow the barrel to
cool between shots. A warm or hot barrel
shoots differently than a cold one. In the
field a shot taken at game is usually from
a cold barrel, so you will want to have your
gun zeroed when cold.
- Making windage and elevation adjustments
- The elevation knob is marked "UP"
with an arrow indicating the direction to
turn the knob to move the point of impact
up on the target. The windage knob is marked
"R" with a similar arrow indicating
the direction to move point of impact to
the right.
Many scopes have a graduated scale around
the adjustment knob which increments representing
a certain amount of point of impact movement
on the target. The most common increment
is 1/4 minute of angle which means one click
or per increment adjustment moves the point
of impact 1/4" at 100 yards.
| Per increment |
25 |
50 |
100 |
200 |
300 |
400 |
500 |
| 1/2 MOA |
1/8 |
1/4 |
1/2 |
1 |
1 1/2 |
2 |
2 1/2 |
| 1/4 MOA |
1/16 |
1/8 |
1/4 |
1/2 |
3/4 |
1 |
1 1/4 |
| 1/8 MOA |
1/32 |
1/16 |
1/8 |
1/4 |
3/8 |
1/2 |
5/8 |
Unit Inch
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