Know your sighting system

            Open Sights—the advantages of open sights or “iron sights” reside mainly in speed and reliability. Open sights do not
rely on glass optics that can break or on electronics that can fail in the field. With few exceptions, open sights are easy and quick
to align, adjustable for range and totally reliable when properly sighted. Most iron sights are integral to the firearm and are
therefore less intrusive and cumbersome than optical sights. One aspect of iron sights that enhances accuracy is the sight radius.
The sight radius is the distance between the front sight post (or peg) and the rear sight. The longer the sight radius, the easier one
may achieve and accurate alignment. The short sight radius of most pistols, not the short barrel, is the reason for their lack of
accuracy at short ranges. This is why long-eye-relief scopes are popular on pistols, not because they improve accuracy but
because they improve sighting.

            
Fixed Sights—the advantage of fixed sights is that they are virtually indestructible. Most other sighting systems may be
“knocked off” when a weapon is dropped, but fixed sights are immune to this possibility because they are fixed, a more of less
permanent part of the firearm. The disadvantage, and one of the reasons for the invention of the “target” or adjustable sight, is
that, if the sight needs to be adjusted, it takes and act of Congress (or just the skill of an able gunsmith) to adjust them.
    The good news is that it doesn’t take a great deal of skill to adjust fixed sights (under all but the most extreme conditions), only
a basic understanding of their working principle. The most prevalent use of fixed sights is found on single action revolvers, usually
of the western reproduction configuration and consisting of a rear notch that travels the entire length of the top strap, with a tall
front sight peg. Since the rear notch generally dictates the alignment of the barrel and thereby establishes a long sight radius in its
own right, problems in sight alignment usually confine themselves to the front sight peg at the end of the barrel; and it is there that
adjustments must be made. If the peg is only slightly off center, you can file one side of it to bring it to center in the rear notch.
Sure, you have to settle for a thinner sight peg, but it solves the problem of alignment and sighting. Most often the problem will
not be with lateral alignment but with vertical displacement. There are two solutions: 1) if you are shooting low, you can file off
the front sight peg to bring the point of impact in alignment with the sighting of the pistol or 2) if you are shooting high, you can
adjust the sight picture from a coarse to a fine bead. A coarse bead is created when you align the tip of the front sight post with
the top of the rear notch. A fine bead is achieved by aligning the front sight post with the bottom of the notch.
    Most problems of high or low impact can be corrected simply by adjusting your sight picture and by knowing the precise
amount of adjustment needed to create the desired effect. This knowledge resides in how much the range of adjustment is of the
entire height of the front sight post; that is, what is the difference in impact when assuming a coarse bead at 25 yards and a fine
bead at the same distance? For instance, set up a target at 25 yards. Fire one round using a coarse bead and fire another using a
fine bead. Measure the distance between the impacts of those bullets. This should typically be about four to six inches at that
distance. Then return to the bench and approximate the halfway mark and fire a bullet with that sight picture. Note the impact of
the bullet. It should be about halfway in between. If not, practice until it is.
    There are few sighting problems that arise which cannot be remedied with lots of practice and an intimate knowledge of the
sighting system.

            
Ghost Ring—the Ghost Ring is designed for fast acquisition. The objective is for the rear aperture or ring to create a
“circle” (or what appears to be a floating or ghost ring) in the aiming eye into which the shooter centers the front sight post. The
experienced shooter assumes this sight picture with both eyes open and then puts the front sight post on the target and fires. With
the Ghost Ring configuration there is only one alignment: the sight post centered in the ring. This reduces aiming to the simple act
of placing the front sight post on the desired point of impact and firing. With both eyes open, the shooter has no problem keeping
the target in the field of view or acquiring a running target within the field of view.
    The main drawback of the Ghost Ring configuration is that it is virtually unusable by those with failing eyesight. The shooting
eye must be able to at least partially focus the ring in the eye. As the eyesight begins to fail, the ring blurs totally out of focus and
cannot be used to center the front sight post. Aiming then becomes more guess work than technique.

           
 Peep Sights—one of the best adjustable, non-optical systems; rather than the ghost ring, this system use a solid rear
sight with a tiny “peep hole” to look through. The front sight post is often shrouded under a hood, effectively creating a front ring
and peg that can easily be brought on target and aligned with the rear aperture. The rear aperture cuts out enough light to make use
easy even to those with failing sight.
    Most peep sight systems have a fixed front sight peg (or one that is not easily adjustable) and a rear sight aperture on a finger
adjustable worm-gear that can be turned up or down. You simply raise the aperture to raise the bullet impact. It is a simple system
that is accurate at long ranges.

            
Optics—optical systems enhance the target aspect by appearing to bring the target closer. They are particularly effective
a longer ranges. They achieve this effect by magnifying the target and limiting the field of view. They enhance this effect by
gathering and focusing light.
    To discuss how this works, it is necessary to define the parts of a variable scope:

•        
Tube—or housing is the outer tube, usually solid piece of steel or aluminum that contains the lenses (ocular lens and
objective lens), magnification ring, erector tube, reticle and eye piece.
•        
Eye piece—a non-lensatic glass that protects the ocular lens and may serve as platform for the diopter adjustment.
•        
Reticles—usually wire cross hairs; can be etched into a reticle glass. There are several basic reticles: 30-30, Pro Diamond,
Truplex, range-finding reticle, Mil-dot, Duplex, and Cats Eye, target dot— to name a few.
•          
Erector Tube—controlled by the external power ring, the erector tube slides back and forth inside the outer tube; the
erector houses the reticle, both the first and second focal plane bells and the lens or lenses that adjust the magnification.
•        
Magnification Ring (or Power Ring)—an adjustable ring, usually just forward of the eye piece; sometimes has a raised
knob to aid in power adjustment. Twisting it slides the erector back and forth in the tube.
•        
Ocular Lens—lens nearest the eye piece.
•        
Objective Lens—lens at the muzzle end of the tube. The larger the objective lens, the more light the scope pulls in. Some
objective lenses are adjustable for range via an adjustment ring on the shank of the objective bell.
•        
Adjustment Turrets—one for windage; one for elevation. Usually located near the middle of the tube. Standard turrets
have turret caps that protect the adjustment screws. Target turrets are adjustable from the outside.  


   
 Optical sights, or scopes, come in a variety of configurations:

1.        Fixed Power – fixed power scopes, except for the diopter, are non-adjustable. Many do not possess the diopter option
either. A diopter adjustment allows the shooter to adjust the focus (or focal point) of the sight to the individual’s eye. With sights
focused to infinity, this is not necessary. With some systems this diopter adjustment may be made by varying the eye relief. The
advantage to fixed power scopes is that they are dependable and simple to use. The usual power range is 2X to 10X magnification,
with 6X being about average. The fixed power scope has the added advantage of a fixed zero; that is, once it is zeroed at a
particular range, it holds the zero to that range. The shooter need only adjust the sight picture to change the point of impact.
2.        
Variable Power—variable scopes are adjustable through a range of powers. The most common range is 3X to 9X
magnification. They are manufactured in two basic types:

     
First Focal Plane Reticle—“The first-plane reticle supposedly has one virtue and one vice. When the magnification in first-
plane scopes changes, the point of impact never shifts—but the size of the reticle in relationship to the target also never
changes…a cross-hair just right at 5X looks like a rope at 10X or shrinks to a fine blond hair at 2X” (John Barsness, American
Rifleman, July 2002, p. 53).
     
Second Focal Plane Reticle—“When the reticle is placed in the second focal plane, behind the power-changing mechanism, the
apparent size stays the same—but the point of impact can change if the tube doesn’t slide precisely back and forth along the same
axis in the center of the scope” (Barsness, p. 54).

3.        
Long eye relief—the long eye relief scope, designed to have an eye relief of a foot or more, have been developed for use
with pistols and revolvers, as well as scout configurations for rifle.


            
Non-Optical (or Holographic) Sights—Holographic sights are similar to optical sights and scopes, but they do not
magnify the target field. The tube has two glass ends with little or no refracting capability. The inner surface of the front glass is
coated with an optical coating upon which a projector projects a colored light (usually red, green or orange). The adjustment
knobs adjust the hologram or dot on the surface of the front lens to the point that coincides with the desired impact point at a
particular distance. Once the hologram is “zeroed” to the desired distance, hold-off may be employed at other ranges. As with any
optical system, once the bullet leaves the barrel all the laws of physics apply.
    Unlike the Laser sight, the holograph does not project light outside its housing.


            
Laser Sighting Systems – Once popular among special units, the Laser Sighting System is very quick and accurate at
close quarters, turning most small arms into a literal point and shoot weapon. A laser projector is attached to the weapon and
adjusted to the desired impact point, usually at short distances. The laser has the distinct advantage of a level trajectory at infinite
distance. Lasers of a light wavelength that resides outside the human range of vision are used in conjunction with long range night
optics to insure a higher level of accuracy and more accurate ranging than optics alone. Such systems are priced outside the price
range of the average citizen (as well as many law enforcement agencies), costing as much as $6,000 or more per unit.
    While the average visual-range laser sighting systems are easy to use, the red or green light projected to the target also paints a
direct line back to the user in dusty or misty air or in high humidity.  All the enemy or bad guy has to do is to aim at the end of the
light and hit the user. The projector can also be seen from the flanks, even when the beam cannot, giving an enemy an equally
good target at a time when the user’s weapon is not pointed at or near him.
    Marking and ranging lasers that can only be seen with night vision devices or detectors are safe to use in an environment in
which only the user is equipped with night vision; but, even then they mark the spot for an equally equipped enemy.
    Visual-range lasers are ill-advised for close combat or distance shooting for the reasons mentioned above. The military, of
course, has solved the problem with rather expensive laser sighting systems configured with light outside the visual range (the
precise wavelength is a closely guarded secret) and goggles designed to detect the light beam and the dot it projects on the target.
Used together with advanced night vision and night vision optics, it’s an unbeatable system—provided the enemy doesn’t have it,
too. [The Latest intelligence is that military lasers are easily detected by the enemy. See
Afghanistan: When the Moon Sets,
Watch Out By Michael Yon.]


Further Reading:  

http://
ezinearticles.com/?Nikon-Scopes-For-Rifles&id=3444349




Find what you need at these websites:

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http://
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http://
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http://
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http://
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SCOPES   RED DOTS   REFLEX  POP-UPS   OPEN SIGHTS
HOLOGRAPH BALLISTIC DROP COMPENSATOR RETICLE
PEEP SIGHT    RANGE-FINDER RETICLE    FIBER OPTICS