Rifles

1 Objective Lens
2 Windage Adjustment
(opposite side of scope)
3 Elevation Adjustment
4 Erector Lenses
5 Power Selector Ring
6 Eyepiece Lock Ring
7 Ocular Lens
8 Eyepiece Assembly
9 Reticle Housing
10 Side Parallax Adjustment
exceptional performance.
11 Tube

DEFINITIONS

The objective lens (or front lens) is critical to a superior sight picture and bright image quality.
The internal erector lenses which right the image.
The reticle, often referred to as the crosshair, provides the aiming point.
The ocular lens (or eyepiece lens) works with the other lenses to magnify
the image, provide correct eye relief, and make diopter corrections. The tube is the diameter of the central part of the scope (1 inch or 30mm). Example: the larger the tube, the greater the scopes ability to transfer a bright image to the shooter. Ring size is based on this measurement.

HOW SCOPES WORK
As light passes through and beyond the objective lens, the resulting upside
down image is sent to the internal lenses. Known as erector lenses, these
internal lenses return the image to a right-side-up position. Finally, the ocular
lens makes a final enlargement of that image and sends it on to your eye.

HOW TO READ THE PRODUCT NUMBER: VX-I 4-12x40mm
VX-I is the Model Series of the Scope
4-12 is the magnification of the image. (ex: four times the size of the image)
40mm is the size of the “objective” of the scope

History

The AR-15 is based on the 7.62 mm AR-10, designed by Eugene Stoner, Robert Fremont and L. James Sullivan of the Fairchild ArmaLite corporation.^[9] The AR-15 was developed as a lighter, 5.56 mm version of the AR-10. The "AR" in AR-15 comes from the ArmaLite name. ArmaLite's AR-1, AR-5, and some subsequent models were bolt action rifles, the AR-7 a semiautomatic survival rifle and there are shotguns and pistols whose model numbers include the "AR" prefix.^[9]

1973 Colt AR-15 SP1 rifle with 'slab side' upper receiver (no forward assist) and original Colt 20 round box magazine


ArmaLite sold its rights to the AR-10 and AR-15 to Colt in 1959. After a tour by Colt of the Far East, the first sale of AR-15s were made to Malaysia on 30 September 1959 with Colt's manufacture of their first 300 AR-15s in December 1959.^[10] Colt marketed the AR-15 rifle to various military services around the world, including the U.S. Navy, Air Force, Army, and Marine Corps. The AR-15 was eventually adopted by the United States military under the designation M16. However, Colt continued to use the AR-15 trademark for its semi-automatic variants (AR-15, AR-15A2) which were marketed to civilian and law-enforcement customers. The original AR-15 was a very lightweight weapon, weighing less than 6 pounds with empty magazine, though later heavy-barrel versions of the civilian AR-15 can weigh upwards of 8.5 lbs.^[11]
Today the AR-15 and its variations are manufactured by many companies and have captured the affection of civilian shooters and police forces around the world due to their accuracy and modularity. (Please refer to the M16 for more history on the development and evolution of the AR-15 and derivatives.)
The trademark "AR15" or "AR-15" is registered to Colt Industries, which maintains that the term should only be used to refer to their products. Other AR-15 manufacturers make AR-15 clones marketed under separate designations, although colloquially these are sometimes referred to by the term AR-15.
Some notable features of the AR-15 include:

• Aircraft grade forged 7075-T6 aluminium receiver is lightweight, highly corrosion-resistant, and easy to machine
• Modular design allows the use of numerous accessories such as after market sights, vertical forward grips, lighting systems, night vision devices, laser targeting devices, muzzle brakes/flash hiders, sound supressors, bipods, etc. and makes repair easier
• Straight-line stock design eliminates the fulcrum created by traditional bent stocks, reducing muzzle climb.
• Small caliber, accurate, light weight, high velocity round (.223/5.56x45mm)
• Easily adapted to fire numerous other rounds
• Front sight adjustable for elevation
• Rear sight adjustable for windage(most models) and elevation (some models. Front sight adjustable for elevation
• Wide array of optical aiming devices available in addition to or as replacements of iron sights
• direct impingement gas system (as designed) with short or long stroke gas piston, or direct blowback opperating systems available
• Synthetic pistol grip and butt stock that do not swell or splinter in adverse conditions (regulated in some states)
• High capacity magazine available where legal
• Ergonomic design that makes the charging handle, selector switch (safety), magazine release, and bolt catch assembly easy to access.

AR-15 sight picture


Semi-automatic AR-15s for sale to civilians are internally different from the full automatic M-16, although nearly identical in external appearance. The hammer and trigger mechanisms are of a different design. The bolt carrier and internal lower receiver of semi-automatic versions are milled differently, so that the firing mechanisms are not interchangeable. This was done to satisfy BATF requirements that civilian weapons may not be easily convertible to full-automatic. Despite this, through use of a "Drop In Auto Sear" or "lightning-link," conversion to full automatic is very straightforward (sometimes requiring slight modification to the bolt carrier).^[12][13] Such modifications, unless using registered and transferable parts made prior to May 19, 1986, are illegal. (The Firearm Owners Protection Act in 1986 has redefined a machinegun to include individual components where a semiautomatic firearm can be converted to full-automatic based on a 1981 BATF ruling on machinegun parts.)
Automatic variants have a three-position rotating selective fire switch, allowing the operator to select between three modes: safe, semi-automatic, and either automatic or three round burst, depending on model. Civilian AR-15 models do not have three-round burst or automatic settings on the fire selector. In semi-automatic only variants, the selector only rotates between safe and semi-automatic. Due to this, weapons modified to full automatic using a lightning-link are capable of full automatic fire only—unless a special full automatic fire select mechanism and modified selector-switch is substituted.


provided by http://en.wikipedia.org/wiki/AR-15#History