Primary Arms SLx 3x Review: 2,000 Rounds Later

Estimated reading time: 10 minutes

The Primary Arms SLx 3x prism sight has lived on my AR-15 for more than three years, through two thousand rounds, rain, concrete, safe bumps, and plenty of regular use. It is not a red dot, it is not an LPVO, and that is exactly why this compact 3x prism sight keeps earning its spot.

Primary Arms SLx 3x Review: The Prism Sight That Refused To Quit

Primary Arms introduced their SLx prism sight in 2021 as an alternative to their popular red dot optics. A prism sight with an etched reticle works with or without battery power and is crisper to the eye than a projected red dot. In 2022, they extended the lineup with the first of its magnified prism sights, including the Primary Arms SLx 3x, which splits the difference between a red dot and a low-powered variable scope.

I purchased the SLx 3x not long after its launch, mounted it to a rifle, and kept it there for over three years of use. That rifle has not exactly been a safe queen. It has been shot, hauled around, bumped, rained on, and generally treated like a rifle optic should be treated. After all that time, this Primary Arms SLx 3x review comes down to a simple question: Does a compact 3x prism sight really make sense on a working AR-15?

Here is how it went.

Primary Arms SLx 3x Specs: Compact Glass With Real AR-15 Utility

The Primary Arms SLx is a compact fixed-power prism sight built around an etched illuminated reticle and 3x magnification. That etched reticle is the whole point. Unlike a projected red dot, the reticle remains visible even if the battery dies, which gives the SLx a useful layer of redundancy. The illumination is there when you want it, but the sight is not helpless without it.

Primary Arms offers the SLx with either green or red illumination via a 2032 watch battery. It also comes in four different reticle styles, including the ACSS Raptor reticle with drop and wind values for either 7.62×39/.300 BLK or 5.56/.308. An ACSS Griffin MIL reticle is also available for shooters who prefer a MIL-based setup.

The optic reviewed here is the Primary Arms SLx 3x model optimized for 5.56 NATO, and that is the version that has stayed on my Smith & Wesson M&P Sport II for the long haul.

Primary Arms SLx 3x Specifications

Model	Primary Arms SLx 3x
Magnification	3x
Reticle	ACSS Raptor reticle
Optimized Caliber	5.56 NATO
Reticle Values	7.62×39/.300 BLK or 5.56/.308
Illumination	Green or red
Battery	2032 watch battery
Brightness Settings	Thirteen settings
Night Vision Settings	Three settings
Adjustment Value	1/4 MOA
Field of View	38 feet at 100 yards
MSRP	$349.99

The ACSS Raptor Reticle Is Where This 3x Prism Sight Gets Mean

The optic in question here is optimized for 5.56 NATO, and the BDC uses a chevron trailed by descending hashmarks for ranging. The top of the chevron is for an assumed 100-yard zero, while the bottom represents 200 yards. The three hashmarks below represent 300, 400, and 500 yards, respectively.

On either side of the marks are sequential dots that allow the shooter to compensate for 5-10 miles per hour crosswinds. The largest part of the Raptor reticle is the horseshoe that rides over the chevron. This allows for gross and quick alignment at close range, but its real purpose is as a lead compensator optimized for a sprinting target traveling approximately 8.6 miles per hour.

That sounds like a lot of information packed into one sight picture, but in use, it does not feel cluttered. The chevron gives you a precise aiming point, the horseshoe gives you fast visual reference up close, and the drop marks are simple enough to use without stopping to do math like you are back in school and forgot there was a quiz.

For an AR-15 optic that is trying to bridge the gap between a red dot and a low-powered variable scope, that matters. A reticle like this has to be fast enough not to punish you up close, but useful enough to justify fixed 3x magnification once distance opens up. The ACSS Raptor reticle does that well.

Hard Housing, Tactile Turrets, And Brightness That Behaves

The Primary Arms SLx 3x is encased in a hard anodized aluminum housing and features fog-proof glass and 1/4 MOA windage and elevation adjustments. There are thirteen settings for adjusting the brightness of the reticle, three of which are compatible with night vision.

When it first debuted, the SLx prism sight came with a short, medium, and high spacer for three different height options. More recently, the SLx is coming with eight options toward that end. What has not changed is the inclusion of Primary Arms’ AutoLive on/off motion technology.

In operation, the windage and elevation adjustments are tactile and can be done with the backend of a 5.56 cartridge case. That is exactly the sort of practical detail I like in a rifle optic. You do not need to dig around for a tool when a spent case will do the job.

The brightness knob is big and easy to manipulate, though it is resistant enough to prevent accidental adjustments while moving around or going in and out of vehicles and storage containers. The option, rather than the need, to have illumination is excellent when working around rapid changes in light and weather conditions.

Why Pick A Prism Sight Instead Of A Red Dot Or LPVO?

Although the Primary Arms SLx has a battery, it is not necessary to power the optic like a traditional red dot. The etched reticle appears like a traditional scope reticle would and is simply illuminated with battery power. I chose the prism sight because of this added redundancy over a red dot, while the 3x magnification was a good balance between a dot and an LPVO.

That balance is the real appeal of the Primary Arms SLx 3x. A red dot is fast and light, but it gives you no magnification. A low-powered variable scope gives you flexibility, but it adds size, weight, and another adjustment to think about. The SLx sits between those worlds. It gives you fixed 3x magnification, an etched reticle, and a compact package that does not try to turn your carbine into a fence post.

At the time of this writing, the MSRP of the Primary Arms SLx is $349.99.

Three Years On An AR-15: The Primary Arms SLx Stayed Locked In

In early 2023, I got my hands on the Primary Arms SLx 3x prism sight. I put it in a medium riser and slapped it on my Smith & Wesson Sport II in 5.56 NATO.

I have gone through multiple AR-15s and several thousand rounds in the time since, but the Sport II has long been my personal rifle and one that always gets a magazine through just to stay sharp. The SLx has been on the rifle almost as long as I have owned it, and it has never come off. Nor will it.

In terms of shootability, the SLx 3x will not impress if you have the option for an illuminated 1-8 rifle scope. It also lacks in the field of view compared to a red dot with no magnification at all. But at its fixed magnification, I found 3x to be a sweet spot.

It offers good magnification and a generous 38 feet field of view at 100 yards without the bulk or need of adjustment of a scope. The BDC works true with my preferred ammunition, and it is not hard to hit point targets at 300 yards. I have not had the opportunity to go out to 500 just yet.

Up close, the magnification only works against you if you have the tendency to shoot with one eye closed. With both eyes open, it is easy to run close-range drills without losing the target in the optic. That is where the SLx 3x starts to make more sense than it might on paper. It is magnified, but it does not force you to treat every close target like a long-range problem.

Two Thousand Rounds Later, This SLx 3x Still Has Its Zero

Through three years of ownership and two thousand rounds downrange, the SLx has taken it on the chin on concrete, taken countless safe bumps, and endured several occasions of sudden pouring rain, without so much as a bit of fog or any loss of zero.

At the onset, I zeroed the optic for .223 Remington 55 grain FMJ and never touched it since. It has never failed. That is not flashy, but it is exactly what you want from an optic that lives on a personal rifle. Set it, shoot it, bump it, forget about it, and have it still be where you left it.

If you are torn between a rifle scope and a red dot, consider any of the Primary Arms SLx prism sights in any magnification that suits you. The Primary Arms SLx 3x is not trying to be everything. It is trying to give you a compact, durable, battery-optional 3x optic with a smart reticle and enough field performance to justify staying mounted. In my case, it did exactly that.

You will not regret it.

Primary Arms SLx 3x Pros And Cons: The Honest Bottom Line

• Pros: Clear fog-proof glass, solid aluminum construction, battery optional for the use of the optic, accurate BDC with select ammunition, useful 3x magnification, simple brightness control, and a reticle that works from close drills to 300 yards.
• Cons: Fixed magnification. It also lacks the wide-open field of view of a red dot and the flexibility of an illuminated 1-8 rifle scope.

Final Verdict: The Primary Arms SLx 3x Earned Its Place

The Primary Arms SLx 3x prism sight is not perfect, but it is honest. It gives you an etched reticle, usable magnification, a tough housing, fog-proof glass, tactile controls, and the kind of boring reliability that becomes exciting after three years of use. On my Smith & Wesson Sport II, it has stayed mounted because it keeps doing the job without drama.

For shooters who want something tougher and more eye-friendly than a red dot, but do not want the size and adjustment demands of an LPVO, the SLx 3x makes a strong case for itself. After two thousand rounds, mine is still there. That says plenty.

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