The number one review request I get is “budget optic reviews.” You’ll see the Primary Arms brand in a fairly high percentage of those reviews, as they consistently deliver quality above their price point.
The Primary Arms Classic Series 21mm Micro Reflex Sight is no different. For a very low price of entry, Primary Arms has delivered a reliable red dot pistol optic in a narrow format, perfect for use with popular firearms like the P365 and G43X MOS.
According to people without an irregular astigmatism (that’s not me), the 3MOA dot reticle is crisp and round. This is born out in photos as well.
The 21mm form factor is fairly narrow, but still large enough to get a solid sight picture. The choice to make this a rectangular screen with a fairly narrow 6061-T6 aluminum housing means that every millimeter of potential screen space is available for use.
That screen space is clear, but with some bluing and slight dimming of the image in low light.
There are 10 brightness settings, but none specific to NV optics.
The Classic Series 21mm Micro Reflex Sight has no “shake awake” or instant on feature, nor is there any automatic brightness adjustment. On the medium setting, a single CR2023 battery (one supplied) should last well over 30,000 hours. That’s almost three and a half years.
I never turned this one off and it’s lasted 3 months and counting. As the battery is mounted on the bottom, you’ll have to unmount, remount, and then re-zero the optic each time you swap out the battery.
You’ll need a very small hex key (one is supplied) to adjust the windage and elevation. Those adjustments should be 1 MOA “per click,” but there are no clicks. I couldn’t hear or feel any response from the adjustment screws. The adjustment itself is very smooth, so as you look through the optic, it’s pretty easy to simply turn the screws and watch the dot move to where you want it.
Despite its low cost, I have no concerns with the Primary Arms 21mm MRS when it comes to reliability. I’ve now put several thousand rounds under this optic through a variety of pistols and a Remington VersaMax shotgun on a Picatinny mount. The dot never moved unless I wanted it to and never failed in any way.
Controls are simple enough; “+” for on and brighter, “-” for dimmer. Hold both buttons down to turn it off. Bare-handed I had no problems getting the controls right, but they were too small to use with any kind of gloves on.
Primary Arms doesn’t list any waterproof rating for the 21mm MRS and there’s none mentioned in the manual. Since it’s an open bottom design, with the battery exposed, water resistance is likely to be minimal. I went ahead and swiped it through the shower spray a few times it while mounted on a pistol there was no ill effect.
What’s nice is that this lower-priced optic is still covered by the Primary Arms Lifetime Guarantee. Primary Arms is well-known for their quality customer service, and their Lifetime Guarantee is great.
The Classic Series 21mm MRS wouldn’t be my choice for a duty optic, but it’s a solid choice for folks on a budget who want or need a reliable red dot sight for their pistol. That’s especially the case for semi-autos with narrow slides, common with today’s popular EDC guns.
SPECIFICATIONS: Primary Arms Classic Series 21mm Micro Reflex Sight
Battery Life: 25,001 – 50,000 Hours
Battery Type: CR2032 3V Lithium Coin
Brightness: 10 Settings
Click Value: 1 MOA
Material: Aluminum – 6061-T6Country of Origin: Made in China
Optic Series: Classic
Reticle: 3 MOA Dot
Reticle Color: Red
Warranty: Lifetime
Weight.: 56 oz
Height: .86″Length: 1.58″
Total windage adjustment: 60MOA
Total elevation adjustment: 60MOA
Price: $149.99
Ratings (out of five stars):
Overall * * *
Zero frills. There’s no “shake awake” or auto on, but the battery will last for years…literally. The dot is crisp and clear, but there’s a little bluing present through the glass. The lack of “clicks” is annoying, but the Primary Arms 21mm Sight certainly handles recoil and never skipped beat. For under $150, the Primary Arms Classic Series 21mm Micro Reflex Sight is a very solid, affordable choice.
