When it comes to mounting an optic to a defensive carbine, the red dot sight has to be the most popular option. Red dots mount like a riflescope but do not have the bulk or the excessive magnification that are a liability for closer shots. Red dots are more precise than iron sights and easier to see in low light as your eyes simply have to follow the red dot and index it onto the target. Price and reliability that used to dog red dot designs are no longer a factory. Battery life is excellent and economies of scale among a growing number of makers ensure that the price of a good red dot is low, even lower than a good pair of iron sights or an entry level rifle scope. But what if you need some magnification? On its own, a red dot doesn’t have any, which puts you at a disadvantage if you have to identify more distant targets or squeeze more accuracy out of your rifle. You might invest some extra funds into a magnifier. Or you might skip this two-step buying process and invest in a prism sight. In my own search for the right rifle sight, I came upon the Primary Arms SLx Micro Prism. My time with the SLx has been short, thus far, but it has taken a fair bit of neglect and a few hundred rounds worth of shooting. It is a straightforward and sturdily built optic that has certainly helped me bridge the gap between the red dot and the rifle scope and it might be worth your consideration.
The Primary Arms SLx Lineup
The SLx line from Primary Arms include a few different LPVOs and several Microprism sights. These sights range from 1x with no magnification up to 5x. All have illuminated reticles powered by a 2032 lithium coin battery, though the reticles vary from model to model. These models have reticles that are specifically calibrated for a given caliber of choice such as 5.56 NATO, 6.5 Grendel, 7.62×39, .300 Blackout, or .308 Winchester.
Find a Primary Arms SLx For Sale
My Optic: Quirks and Features
I have been running a Smith & Wesson M&P Sport II in 5.56 NATO for several years. For the money, it is an excellent little rifle. It comes with an A2 front post front sight and a rear MBUS folding peep. These sights work fine, but like most irons out there, you can’t readily pick them up in low light and the front sight tends to cover up targets at greater distances. I tried a few red dot sights and found them to be an improvement, but without magnification, the dot tends to bleed large on targets at 300 yards and beyond. The red dots, on their own, are fine for targets at that distance that want to be seen. I wanted more magnification. The optic I landed on is the Primary Arms SLx 3x MicroPrism. There are versions of this site: one with a ACSS Griffin X Mil Reticle–with ten MILS of elevation and one with an ACSS Raptor reticle with five MILS, regulated for either 7.62×39/.300 BLK or 5.56/.308. Mine is the MicroPrism with the ACSS Raptor reticle calibrated for 5.56.
The MicroPrism is all aluminum in construction and comes in at under eight ounces with the battery installed. The windage adjustment is on the right side of the sight, while the elevation adjustments are made on the top. Each click of these adjustments equals 1/4 MOA. The left side houses both the battery and the illumination dial that has 13 brightness settings as well as three settings that are compatible with night vision.
Mounting the MicroPrism is as simple as any other optic, but Primary Arms supplies a set of spacers to adjust the height of the optic. The mount will fit any standard 1913 Picatinny rail. The straight spacer can be mounted and used on rifles that come optics ready (ie no iron sights). The medium cantilever sight, which came mounted from the factory, proved to be just right on my rifle. It positions the optic just high enough to clear the A2 fixed post front sight of my rifle.
The ACSS Raptor Reticle
The ACSS Raptor Reticle on this model can be illuminated red, but it is also etched black into the glass of the optic, allowing the optic to be used without the battery. This is an appealing feature of prism sights over red dots. The Raptor reticle itself has a lead compensator, ballistic drop compensator, and wind compensator built in.
The reticle consists of a pronounced horseshoe that can be used to lead left or right on a moving target. Primary Arms states that the lead compensator is scaled with a target moving at approximately 8.6 mph. That’s fairly quick, considering I run a nine minute mile.
The BDC consists of a chevron followed by descending hashmarks that vary in size and spacing depending on the caliber you select. The top of the chevron represents a 100 yard zero, while the bottom, 200. The first hashmark represents 300, the second, 400, and so on. The width of the hashmark is scaled to encase a target 18 inches wide to allow you to gauge roughly how far a target is. The further the target is, the smaller it appears on the hashmark and the further the distance. Once the target is filled in the appropriate hashmark, you have the range and drop already figured out.
The Raptor reticle also uses a set of etched dots to help the shooter compensate for wind. The dots measure holds over for 5-10 mile per hour winds.
There is no stated nominal battery life, but the MicroPrism is equipped with Primary Arms’ AutoLive motion sensing technology. When the gun is not moving, the optic shuts off. When it is in motion, the reticle illuminates once again.
On the Range
The manual provided with the Primary Arms MicroPrism includes approximate ballistic figures on different cartridges and how to use that information with the optic in order to sight in the rifle for a given distance. To sight in the MicroPrism, I did it the Cajun way. When all else fails, follow the directions.
I set up a clean paper target at thirty yards and hooked my Sport II into a Caldwell Matrix rest and started shooting. My ammo of choice is Frontier .223 Remington 55 grain FMJ. This round is the most accurate in my rifle with its 1:9 twist rate. Under the shade of a roof, I cranked up the illumination and the black reticle popped up easily on target. I fired one round, which favored high and right. After four more rounds, I was able to walk those rounds into the bullseye, making adjustments to the windage and elevation knobs with a screwdriver as I went. At this close distance, I had a good field of view. The target appeared larger with the 3x magnification, but not so much so to need to hunt for it in my field of view.
After cooling my barrel, I set another target out to 100 to get the rifle zeroed at a more realistic distance. Through my scope I was surprised how sharp the illumination was on target at that distance in bright 103 degrees of sunlight. At 100 yards, the Primary Arms MicroPrism has an advertised field of view of 38 feet and I certainly believe it. My field of view was not obstructed but I could still see the bullseye clearly. I could also scarcely make out my shots as they struck high at that distance. I cranked down the elevation and was on the money.
From that distance, I put up a clean target at the same distance and tried for groups. To bring myself back into the equation a little bit, I switched rests to a Caldwell Rock Jr. The hard GI trigger on my Sport II did not do me any favors, but I was able to squeeze five rounds of the Frontier .223 load into groups under three inches.
Based on experience with this particular rifle, my groups using the same ammunition when paired with iron sights or a red dot like the Sig MSR, are marginally wider. The big difference is that the MicroPrism has a crisper reticle, allowing me to put rounds downrange faster and see some of the impacts. In more tactical words, faster follow up shots and hit conformations.
The problem with a magnified optics is that they magnify your field of view and you could miss your actual target and have to find it before lining up a shot. At close distances, that can cost you too much time. I stepped up to a pair of paper torso target sitting at 30 yards and engaged them offhand in a set of double-tap drills. Two rounds on the left target, two on the right, two on the left again.
At that distance, the magnification is unnecessary but not a hinderance. The generous eye relief of the MicroPrism, allowed me to keep my eye a full three inches from the glass. With both eyes open, I could easily find my targets and transition between them. I am no operator, but I was able to clean the drill in 5.2 seconds. These same drills, done at different times with the same rifle but different gear, were cleaned at six seconds using iron sights and 4.8 seconds using a Sig MSR red dot.
The Primary Arms SLx optic is available up to 5x of magnification, but given how it did in close drills, the 3x is cutting the edge toward a sweet spot. The same could be said when it came to stretch my rifle’s legs out to 400 yards. The targets were 18 inch wide steel torsos. I engaged them from the prone position rested off of a shooting bag.
The range hashmarks worked perfectly in sizing up my targets at the prescribed distances. I could hit them easily in still air and with a wind that kicked up around me by holding over using the wind drift compensation dots. The only misses I could count was due to downrange wind that is harder to perceive.
In the time that I have had the Primary Arms MicroPrism 3x sight, I have put two hundred rounds downrange. The sight was not tortured in any way, but it take some neglect. The sight’s illumination turned on at the start of my first range trip and it is still on and still burns brightly one month on. It also endured plenty of hard knocks coming in any out of a safe and a thunderstorm soak. But time after time at the range, the optic woke up and shot without a loss of zero. Although a red dot might be a slightly faster option at very close distances, a prism sight is not ungainly and it surely excels at distances where a red dot lacks without the drawbacks of a conventional rifle scope. For me, the MicroPrism 3x represents a best balance in the world of tactical optics.