Red-dot sights, low power variable optics and prism sights are the three main styles of optics for AR-15 carbines
Optic options abound for the AR-15. The most popular choices are red dot sights, low-powered variable optics, and prism sights like the military-issued ACOG.
Each of these choices has strengths and weaknesses, the trick is to find the glass that best fits your needs.
Red Dot Sights on AR-15s
These simple and effective optics are my top choice for most AR-15 use.
These small sights have an internal emitter that projects a red dot up on the glass through which the shooter aims and are ideal for use inside 200 yards.
Red dot sights usually consist of an aluminum housing, some internal circuitry, and glass lenses.
The efficiency of these designs means battery life is measured in tens of thousands of hours, so they can be turned on and left on. This ensures the rifle is always ready when it’s needed.
They are simple, robust, and relatively inexpensive.
The red dot projected on the optic’s glass should be sharp and clearly defined, but that’s not always the case with older eyes or for shooters with even mild astigmatism.
If the dot appears oddly shaped or blurry, the shooter likely has a small vision issue that will impact the effectiveness of the optic.
In these cases, it’s better to look for another solution.
Low-Powered Variable Optics (LPVO)
Scopes with magnification ranges of 1-6x up to 1-10x fall into this category.
The ability to use the LPVO like a red dot sight or to turn up the magnification and use it as a traditional scope makes these appealing to many shooters.
They offer the best of both worlds. Shooters on a budget desiring an LPVO that they can use like a red dot optic by setting it to 1x should purchase LPVOs with second focal plane (SFP) reticles and fiber optic illumination systems.
In an LPVO, this illumination system gives a bright and clear aiming point under any lighting condition, just like a red dot sight.
Shooter’s desiring first focal plane (FFP) reticles in an LPVO that also want to use it like a red dot need to select optics with diffractive illumination systems.
One way of knowing if an FFP LPVO has such an illumination system is it’ll cost more than $2,000.
This is the only way to make a first focal plane reticle truly daylight bright with a small 2032 battery.
Second focal plane reticles make much more sense in LPVO for this reason.
Prism Sights for AR-15s
These are fixed-power sights that have simple and robust illumination systems and few moving parts.
They are the ideal combination of simplicity and durability.
The downside is the shooter needs to pick a magnification range prior to purchase because that detail cannot be changed after purchase.
Most prism sights sit in the 1.5x to 4x range.
That magnification range allows the shooter to better see the target while still retaining the ability to use it as a red dot sight.
Prism sights with an external section of fiber optic can be used in a similar fashion as red dot sights, just with a small amount of magnification.
That magnification is useful for accuracy at extended ranges. Take note that prism sights that run on a 2032 battery will not be bright enough to use the reticle as a red dot sight in the brightest daylight conditions.
Red dot sights reign supreme for general use scenarios because they are simple and robust.
Prism sights are equally robust but offer the option of magnification and don’t suffer from misshapen aiming points due to astigmatism.
LPVO can extend the range of an AR-15 out to 1,000 yards and beyond, but the ability to use one like a red dot sight depends heavily on whether it’s a FFP or SFP reticle and the illumination system that comes with it.