I was looking around for a prism sight to replace one of my red dots on an AR rifle. I was tired of the flared out dot due to my astigmatism. So when the chance came along to get behind the Primary Arms SLx 1x prism, I was literally a kid in a candy store. The Primary arms SLx worked great as the red dot replacement.

The SLx 1x prism had all the features I wanted in a true 1 power optic. For one, it was a prism sight. Therefore it has an etched reticle, like most magnified optics. I really like this as a feature, it takes away the burst that red dots have for me, and it gives an actual reticle, even when not illuminated by the battery. I’ll get to the actual reticle later. The SLx’s reticle illumination is red, but green is also an option. Another feature that I wanted was good eye relief. Since it’s not a red dot style optic, eye relief is important. The SLx has a stated 2-6” of eye relief. But it really feels like more. I can get right up on the optic or back off even more than the 6”s and still get a good sight picture, so much so that it feels very much like looking through a red dot optic.

Primary Arms gave the SLx 1x prism their ACSS Cyclops gen II reticle. The ACSS (Advanced Combined Sighting System) Cyclops is a horseshoe style etched reticle with a chevron, think triangle, in the middle. The round horseshoe part gives extremely fast target acquisition, especially for close up targets. It is also about the size of a 00 buck pattern at 25 yds. The chevron then takes over for precise aiming. You can also use the chevron like you would a red dot, if up close. The top point of the chevron is where you would zero your rifle. This point is also where you get pretty precise aiming by just putting the point on the target. The zero depends on what barrel length and caliber you are using (see picture). With a 16” 5.56 barrel, it would be 100 yds. The inner point of the chevron is now a bullet drop compensator. So with the same 16” barrel, this would be for 300 yds. Then the bottom part of the chevron would be 400 yds. The BDC is just a close estimation, since it also depends on ammunition type and the height at which the SLx is mounted. There is also range estimation built into the SLx. It uses a 5’10” tall or 18” wide object for range estimation. When sighting in, the SLx has 1 MOA clicks for both the windage and elevation adjustments. The clicks are very positive. The adjusting dial is recessed into the SLx’s housing so that the adjustments won’t be hit and knocked out of zero. It also makes for a smoother look. Even though the 1 MOA adjustments worked fine, since the SLx has the precise chevron aiming point, I would have liked to see more accurate adjustments, maybe more like ¼ MOA, or even ½ MOA.

Illumination comes from a CR2032 battery that rides inside the brightness knob. The SLx has 13 brightness settings. The highest are “daylight bright”, and the lowest 3 are for night vision. Yes, the “daylight bright” does illuminate the reticle in bright sunlight. It’s not quite as bright as a quality red dot, but you can still see that it is a brighter red. My biggest complaint about the SLx is it’s mushy and hard to turn brightness knob. The click between levels just suck, plus it’s hard to get the dial to turn to them. If it had better “clicks” I wouldn’t complain as much about the stiffness. But, on the other side of that is the awesome “Autolive” function. This is a motion activated auto on function. After a certain time of no motion, the illumination will turn off. Then, when it gets moved, even just a little, the reticle turns back on to the last brightness setting it was on. The Autolive works fantastic, see this as to how well it works: YouTube Video. Because of the Autolive function, battery life is greatly extended. In fact, Primary Arms states the battery life to be 29,000 hours on the medium setting! Remember, if the battery dies, you still get the advantage of having an etched reticle, it’s just no longer illuminated.

The SLx gives a very clear window in which to look through. I found this prism sight to be way clearer than I expected from a $250 optic. It has a pretty good Field of View at 76.5 ft @ 100yds. It has a very forgiving eyebox and even has a diopter to focus in the reticle for your eyes. Even when looking through the SLx at odd angles, I was still able to get a good sight picture.

The Primary Arms SLx 1x prism comes with a variety of mounting options, all of which are included in the package. The SLx comes with 4 spacers and a picatinny rail mounting base. 3 of these spacers are cantilevered, the other 1 is straight. This lets the SLx mount right above the rail, with no spacers, or up super high off the rail with the straight spacer plus the high cantilever one, and anything in between (see picture). Of course all mounting screws and wrenches are included to swap the heights around. Oddly enough, the SLx can also be mounted to a carry handle of an AR. All these height options let you tune the height, so if you are using a magnifier or back up iron sights, you can get it just how you like it. Yes, the SLx prism will work with those too.

This is not on full brightness, more like around setting 7 of 13, in full sun

Primary Arms did a fantastic job with the SLx 1x prism. It does almost everything I wanted it to do, okay, it does everything I need it to do. The clarity is great, it’s bright, has auto on/off, good battery life, and even works without the illumination. The 1x appears to be a true 1 power to me. Everything close up and far away is clear and size appropriate. Shooting with both eyes open is just like shooting with a non magnified red dot, plus no starburst. Having the ability to mount the SLx at various heights is also nice. I like this optic so much that I might even mount it on my “go to” rifle. Go check out the SLx 1x prism at Primary Arms.

Firearms Insider Reviews - 8 Key Points

Claim to Fame:

Etched reticle micro prism sight

Target Market:

Anyone wanting a solid 1x optic

FNBs (Features & Benefits of this product):

ACSS Cyclops Gen II reticle
13 Illumination settings including Daylight Bright
3 Night Vision Settings: Low, Med & Flood
AutoLive motion-sensing on/off battery saving technology
29,000 Hour battery life at medium setting
Includes 8 Mounting Height Options (incl. Absolute Co-witness & Lower 1/3 heights)
Length: 2.48”
Weight: 7.6 oz with height riser (only 5.5 oz without riser)
Etched Reticle
Diopter for precision reticle clarity
Eye Relief Range: 2” to 6” with 3.6” for optimum Field of View
Field of View: 76.5 ft @ 100 yds
120 MOA total Adjustments
1 click = 1 MOA
Fully Multi-Coated optics
IP67 Waterproof, nitrogen purged for fog resistance, and dust proof
Uses (1) CR2032 Battery (Included)
Lens Covers included
Backed by Primary Arms Lifetime Warranty

What other aesthetic options or finishes are available?

Green reticle or FDE housing

What others are saying?:

4 out 5 stars @PrimaryArms

MAY BE MY NEW FAVORITE OPTIC!

Put this on an AR15 in 5.56 and the performance was fantastic. The included mounting system is excellent, the reticle is outstanding and the field of view for such a small optic is surprising. I like the etched reticle and the brightness settings are perfect for all lighting conditions. Up until now my favorite optic was the Trijicon MRO but at half the price red dot is hard to beat. Seems just as if not more so rugged that much more expensive options. The only drawback and it's a small one is the 1 MOA adjustment increments which could make it difficult to really dial it in at range but out to 50 yards on my rifle it was dead on.