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One of the newest developments in firearm optic technology is the prism scope.
If you’ve been shooting for a while, prism scopes may seem unfamiliar to you. Yet, these new optics have become one of the hottest trends in the rifle optic world, recommended for use on AR-15s, AR-10s, and other tactical rifles.
Discover what prism scopes are, how they work, and how they compare with red dots, LPVOs, and other popular optics.
Of Prisms and Lenses
If the first question on your mind is, “Just what are prism optics,” you’re not alone. Prism scopes, also called prismatic scopes, are still very new on the market, which is why many shooters are unfamiliar with the term.
At first glance, prism scopes seem to resemble red dot sights, and they may even seem to have red dot-like reticles. However, they function using very different technology and manufacturing techniques.
The most critical difference between a prism scope and other optic types is the optical device employed.
Traditional Rifle Scopes and Lenses
You may already know that traditional optics use glass lenses. A typical rifle scope uses at least two; the lens closest to the end of the barrel is called the objective lens, and the one closest to the shooter’s eye is the ocular lens.
The objective lens transmits light to the ocular lens, magnifying it according to its current setting (either fixed or variable).
The lens size and construction and the distance between each lens affect many of the scope’s traits: magnification rate, image quality, parallax, focal plane, etc.
The New Big Thing: Prisms
A prism optic uses a glass prism to focus the light, eliminating the need to use a set of lenses and allowing a typical prism scope to be much more compact than a traditional rifle scope.
Though the use of prisms in optical gunsights is a recent development, the technology is proven, used for many decades in binoculars and spotting scopes.
Like modern scopes, prism scopes feature etched reticle systems, directly laser-etched into the prism, with or without illumination.
Advantages and Disadvantages of Prism Scopes
Now that you know how they work, the next question on your mind is probably “What are prism optics capable of?”
As with everything else when it comes to firearms, every choice is a compromise. Prism scopes offer many advantages but also possess some drawbacks that you should know before buying.
Although a typical prism scope features dimensions and reticle systems very similar to that of a red dot sight, prism scopes may also offer fixed magnification, typically ranging between 1x and 5x.
In a certain sense, a prism scope can bring together the benefits of a red dot sight and a fixed-power scope, offering a high field of view with magnification.
Not every prism scope has magnification; the lower-cost models feature 1x-1.5x power prisms and are closer in dimensions and performance to a red dot sight. These models also tend to be attractively-priced, offering quality at a lower price point than equivalent popular red dots.
Nonetheless, even the low-power models may be a better choice than red dot sights for some shooters. Because light is reflected through a prism instead of lenses, the image clarity is brighter and sharper, allowing for faster target acquisition.
An understated advantage is the presence of an adjustable diopter, allowing shooters with specific eye conditions (astigmatism, etc.) to adjust the scope and obtain a clear reticle.
Prism scopes are often the definitive answer for such shooters, as they tend not to see a sharp reticle when looking through a regular red dot sight; they instead see a “comma” or blurry smears, making it difficult to focus and stay on target.
Prism scopes have some of the disadvantages of regular rifle scopes; they possess an eye relief, which tends to be shorter than that of a standard magnified scope.
Although prism scopes may feature magnification, the use of prisms limits the practical maximum magnification.
Currently, there exist no prism scopes with more than 5x power. If you need more magnification, you must use a traditional lens-based optic.
The eye relief issues apply even on the low-powered models. Some shooters may criticize having to find the right eye and head position in exchange for no magnification, finding them far less convenient and easy to use than red dot sights.
Prism scopes may experience parallax issues, the same as with traditional rifle scopes. However, they are relatively minimal and easily resolved with a proper shooting stance (good cheek weld, head position, body position).
Applications of Prism Scopes
Although prism scopes are not perfect, their traits and advantages make them ideal for AR-15s and similar tactical rifles and carbines.
The overall dimensions, reticle system, and magnification ranges of a typical prism scope mean they compete with red dot sights, low-powered traditional scopes, and LPVOs, offering another potent choice to AR-15 shooters looking for a close-to-medium range optic.
Although most prism scopes do not go beyond 5x magnification, this is plenty if you intend to keep your shooting within 300 to 500 yards. Many shooters have “too much scope” for their intended purposes; a prism scope can help make the rifle build more focused.
It is essential to understand that prism scopes do not replace existing optics and are not objectively better than any other type.
If you need an optic for a carbine exclusively intended for close-quarters (home defense, competition, etc.), a prism scope will work fine, but a red dot or a holo sight will be a better, lighter, more reliable option.
If you’re shooting at extended distances regularly, prism scopes will simply not give you the magnification you need.
However, prism scopes are an excellent choice for hunting ARs, as virtually all of them feature illuminated reticles and superior image clarity. They are also a good choice for scout rifles and survival guns.
Lastly, they may function as an effective alternative to an LPVO for a “do-it-all” all-purpose carbine or rifle, especially in an intermediate caliber such as 5.56x45mm, .300 Blackout, or 7.62x39mm.
For shooters with astigmatism (or a similar eye condition), who have difficulties “reading” a red dot sight, the prism scope may well be the only practical option, as very few optics of other types feature diopter adjustment.
Although prism scopes are still new and relatively untested, they are rapidly gaining acceptance in the tactical shooting community, offering an exciting alternative to other, more established optics.
Consider installing a prism scope if you find that neither red dots nor LPVOs would suit your particular rifle build.