Primary Arms SLx PAC2.5x Compact prism sight
We tested the Primary Arms SLx 2.5 Compact PAC2.5x fixed-magnification prism sight – not exactly the latest entry in the company's catalog, but still a solid, reliable, and overall affordable alternative for hunting, competition shooting, and law enforcement applications, particularly on AR-15 variants and other modern sporting rifles thanks to its versatile ACSS reticle
The market for budget-priced optics for modern sporting rifles – AR-15 platforms, AKM variants, and so on and so forth – is a pretty crowded one, addressing the needs of both civilian customers (hunters, sport shooters) and law enforcement customers.
While up until not too long ago a low price was almost invariably synonymous with low quality, the evolution of materials and manufacturing technologies in the past decade or so have allowed multiple companies to make nothing short of a quantum leap in the price-to-quality ratio of their optics. The example of brands such Sightmark shows that offering budget-priced optics that are completely dependable is today eminently possible.
Among the companies that fight for primacy on the glutted budget-priced optics today is Texas-based Primary Arms, established in 2007 and currently a major global player, offering a plethora of alternatives manufactured mostly by suppliers in China, Japan, and the Philippines.
Primary Arms PAC2.5x prism sight – right side, with flip-up lens caps
Primary Arms PAC2.5x prism sight – right side, installed on Picatinny rail
In the past decade, Primary Arms built itself a solid reputation on the US market. Now, its products are gaining a foot hold on the European market as well, particularly with recreational and competition shooters. And among the many models that the company currently offers on both sides of the Atlantic Ocean, the Primary Arms SLx 2.5 Compact prism sight, best known as PAC2.5x, while not exactly one of their latest, is definitely one of their most respected – and interesting.
The Primary Arms PAC2.5x is a fixed power 2.5x32 prism sight, built for short-to-mid-range engagements with modern sporting rifles, pistol-caliber carbines, sub-machine guns, and the like; but its capabilities go way beyond the typical close quarters of such platforms.
The PAC2.5x sight is built around a black hard-anodized, single-piece 6061-T6 lightweight aluminum alloy body. The protective screw-on caps for the adjustment dials, the reticle illumination dial and the battery seat cap are also manufactured out of the same material; the only polymer components are the issued flip-up lens covers. The Primary Arms SLx 2.5 Compact PAC2.5x prism sight is completely fogproof, waterproof, and nitrogen-purged to resist environmental aggressive.
All the glass components – from the prism down to the objective and eyepiece lenses – are manufactured out of a superb quality optical glass, offering quite a remarkably high level of light transmission and image clarity for an optical sight in its price range.
The PAC2.5x features an integrated slant mount with a two-piece screw-on mounting interface for Weaver or Picatinny rails, which can be removed and replaced with quick-detach interfaces (sold separately), from either Primary Arms or third-party suppliers. The mount is ACOG-style, meaning that by removing the two-parts mounting interface for Picatinny rails, the PAC2.5x sight can be installed on firearms such as AR-15 variants with A1 or A2 type fixed charging handles.
Once removed, the Picatinny interface can also be reinstalled in a specular position – if, for example, the shooter needs the screw knobs out of the way of a side-mounted charging handle. The sland mounting base keeps the sight closer to the shooter's eye, quite the convenience when installing the PAC2.5x on bull-pup firearms or short-barrel rifles. A multi-position (-2 to +2) diopter adjustment dial is integrated on the eyepiece.
Two screws are located on top of the PAC2.5x tube, allowing the installation of a Picatinny rail segment (sold separately) to piggy-back the SLx 2.5 Compact with a small red dot sight.
The Primary Arms PAC2.5x prism sight features a first focal plane etched ACSS-CQB reticle, illuminated in red and powered by a single CR2032 battery. The illumination can be set manually on twelve different levels, depending on the environmental light conditions, while a set of two capped, recessed turrents allow fine adjustment of the reticle. The ½ MOA clicks aren't just as tactile as one would expect, but offer an excellent auditory feedback; the edge of the turret caps can be used as an adjustment tool.
Primary Arms ACSS-CQB etched reticle
The recessed, capped adjustment turrets
The ACSS reticle, illuminated
A Primary Arms patent and exclusive, the ACSS (Advanced Combine Sighting System) reticle has been designed to get shooters on target extremely quickly up to a 600 yards (approx. 584 meters) range, while retaining swift and easy close quarters engagement capabilities.
Specifically, the Primary Arms SLx 2.5 Compact PAC2.5x prism gunsight features an ACSS-CQB reticle set for out-of-the-box use with popular MSR calibers such as 5.56x45mm NATO, .223 Remington, 5.45x39mm, and some .308 Winchester (7.62x51mm).
Making the right math, however, it can easily be adapted to some 6.8mm, 9mm, and .300 BLK loads as follows:
The ACSS reticle features a wide outer horseshoe for CQB and a smaller center donut with four descending dots for longer range engagements; the smaller descending dots allow the shooter to engage targets from 50 all the way fown to 600 yards (45 to 550 meters, approximately).
Two sighting ladders are located at the sights of the outer horseshoe, and are conceived to help the shooter with ranging on targets that are approximately 5'10" (170 cm) tall or 18" (45 cm) wide; two additional dots located at the sides of the inner donut allow engagement of targets moving at an average speed of 8.6 miles per hour (approx. 13 km/h) at 100-300 yard ranges.
More specifically, the ladder on the left side of the horseshoe is meant to range the target based on its height, while the one on the right side provides ranging based on the target's width.
Once the target is properly ranged, the shooter will be able to engage it by using the smaller dots under the center donut if it's a standing target, or use the side dots if it's a moving target.
This superb level of versatility makes the ACSS reticle an excellent choice for civilian uses (hunting, sport shooting, personal defense, property protection, cattle protection against predators, etc.) as well as for law enforcement and private security personnel.
The ACSS reticle is compatible with flip-to-side magnifiers; unfortunately the PAC2.5x prism sight does not offer an illumination level that is compatible with night vision devices, which may very well be its main drawback.
We spent essentially the whole Summer of 2022 putting the Primary Arms SLx 2.5 Compact PAC2.5x prism sight through its paces (including some quite heavy ones) on the author's favorite test-bed – a personal Faxon Firearms ARAK-21 long-stroke piston-driven build with an 11" barrel, on a BAD-556 lower and a SIG Sauer MCX stock.
What we quickly found out is that, that if there's something that the PAC2.5x really excels in (aside from the staggering quality of the optical glass), is its capability to hold zero.
There's almost nothing that the average user can do in normal conditions – at the range, in competition, or while on duty – that can cause the Primary Arms PAC2.5x to lose zero, much less inflict any serious sort of damage to it, outside of deliberate and aimed distructive behaviours. Mishandling or getting rough on the turrets isn't going to cut it either. They're extremely good at holding zero.
The level of performance and dependability of the PAC2.5x is high enough to be recommendable for professional use, in law enforcement and private security if not for military applications.
Standing at 12 centimeters (4.8") in overall length, and weighing in at approximately 417 grams (14.74 oz), the Primary Arms SLx 2.5 Compact PAC2.5x prism sight will not even add too much weight on to your rifle or carbine.
A generous 10,16mm (0.64") exit pupil, a 6,85 cm (2.67") eye relief and an 11,4 mt / 3.75' field of view at 100 yards, along with the low fixed magnification factor, makes the PAC2.5x extremely easy, fast and comfortable to use with both eyes open, without image distortion or difficult focus, and without causing eye strain to the user.
The Primary Arms SLx 2.5 Compact PAC2.5x prism sight is sold with a bare kit, which however contains everything you'll need to install and operate it right out of the box, including a CR2032 battery. Other than the aforementioned top Picatinny rail segment or optional interface brackets, the only accessory sold separately is a black honeycomb anti-reflection device (killflash).
The Primary Arms PAC2.5x prism sight is available on the US market at a manufacturer's suggested retail price of $249.99, while on the European markets it's available at variable prices depending on the Country, but generally under €270: a perfect choice for shooters and professionals who are looking for an affordable sight that won't break the bank and still remain dependable and high-performing for decades to come.