September 14, 2021
By James Tarr
Primary Arms has been producing intriguing optics for a while now, not content to imitate other companies but rather doing their part to innovate. Their new SLx 1X MicroPrism is one of the most interesting optics I’ve encountered in years.
A prism optic actually uses a glass prism to focus an image as opposed to a traditional riflescope which uses a series of lenses. Prism scopes, due to their design limitations, are fixed power and usually on the lower end of magnification (below 5X).
Prism scopes have etched reticles, so even if the battery dies you still have a nice, solid, black reticle. If you’ve got an astigmatism (like me), red “dots” always look like squashed grapes, whereas etched reticles are crisp, illuminated or not. Their traditional weakness? Because they use lenses (like a traditional scope) they have a limited eyebox, unlike most red dots which have nearly unlimited eye relief and are very forgiving in side-to-side movement.
The SLx 1X MicroPrism has the largest eyebox I’ve ever seen in a prism scope, and in fact, it is nearly as large as you’d get with most tube-type red dots, in every direction. Primary Arms says usable eye relief is two to seven inches (with perfect relief being a generous 3.6 inches), but it’s honestly far more forgiving than that. If you can physically see through the scope, the reticle is usable. Any place on your upper receiver you’d normally mount a red dot you can mount, and use, the MicroPrism.
Because of its short length, less than 2.5-inches long, field of view (78 feet at 100 yards) is huge. The optic itself weighs only 5.5 ounces. FYI Primary Arms also sells a 3X MicroPrism which has the same proportions but is just slightly bigger.
The Micro Prism features the ACSS Cyclops G2 reticle, which has a large 65 MOA horseshoe over a small chevron for both speed and precision. There are 13 brightness settings, with the highest truly daytime bright and three meant for night vision, and the optic even has AutoLive motion-sensing technology which shuts off the illumination for maximum battery life (advertised at roughly 30,000 hours, depending).
The glass in this optic seems crisp and isn’t visibly tinted at all. It’s shockingly small for what you get, has an IP67 waterproof rating, and comes with spacers and bases for eight different mounting options, all for the amazing price of $249.99. If you don’t like their mounting options, the MicroPrism uses the Trijicon mini-ACOG screw pattern, and many companies (like LaRue) offer different mounting options for the mini-ACOG.
The only real complaint I’ve heard about this optic is the “crude” windage and elevation adjustments of only 1 MOA, which help keep the manufacturing costs down. I don’t consider that a valid complaint. At most you’ll be half an inch off at 100 yards, or a quarter-inch at 50. For 99.5% of people, between the type of firearm this optic is intended for and their eyesight, that will be within margin of error.
I first tested this optic on a Smith & Wesson M&P15 TII rifle. I went to work on silhouette targets from point-blank range out to 50 yards. The little prism optic is a true 1X and allows two-eyes-open shooting. It was a sunny day at the range, and I tried some transition drills between IDPA targets set 20 yards from me, first with the illumination on and then with it shut off. I was able to use the horseshoe as a giant red dot when running and gunning. It was thick enough that in sunlight I was just as fast with the illumination shut off. On a cloudy or dark day or indoors I’d definitely want the illumination on. No matter what optic you put on your rifle, you should use it under various weather conditions to figure out what works best for you. Time spent at the range testing your gear is never wasted.
I have since mounted this optic on my Daniel Defense Mk18 pistol, which is my current truck gun, and zeroed it at 50 yards. After a month of driving around I went back to the range and rechecked zero—still on. Between the S&W and the DD I’ve put several hundred rounds through guns with this optic attached, without any problem. Prism scopes are simple, which means they’re harder to break. Only the small eyeboxes have kept them from becoming more popular than they are, and with the MicroPrism that is no longer an issue.
The great thing about this optic is the etched reticle—even if the battery dies, I’ve still got a reticle, which is why I think it’s a great idea for a truck gun.
Is it a good idea to have an optic on hand that is not battery dependent and will work when society collapses or a hostile nation sets off an EMP? Well, it’s not a bad idea….