Primary Arms
Primary Arms SLx MD-21 ACSS CQB
A compact 20mm push-button microdot with four selectable ACSS CQB reticle modes, AutoLive, and 100 MOA of travel per axis.
Quick Specs
- Price
- $200
- Weight
- 5 oz
- Brand
- Primary Arms
- Category
- optic
Features
- •ACSS CQB red reticle with four selectable modes
- •20mm clear aperture
- •Standard microdot footprint
- •Low mount and absolute cowitness mount with spacer included
- •CR2032 battery
- •12 brightness settings, including 3 night vision settings
- •5.0 oz, 2.8 in long, cast housing
Capability Boosts
Recommended For
+19 more
Compatibility Tags
Overview
The SLx MD-21 packages a 20mm clear aperture into a 5.0 oz, 2.8 inch body. That makes it 1.5 oz lighter and 0.2 inch shorter than the MD-25 Gen 2, while its push-button controls provide 12 brightness settings with three night vision levels. AutoLive handles wake-up, and low-battery plus high/low setting indicators communicate power and control status.
Its ACSS CQB reticle can show all elements or isolate useful combinations. Hold either brightness button for three seconds to cycle through all features, chevron plus BDC, chevron plus horseshoe, and chevron alone. The open-top horseshoe gives a large shape for fast pickup, the chevron supplies a precise zero and ranging references, and the three stacked dots extend the calibrated drop ladder.
The SLx has the same 0.5 MOA clicks and 100 MOA of travel in each axis as the GLx MD-21s. It also shares the low mount and absolute cowitness mount with spacer, which set center heights of 1.41 and 1.535 inches. The difference is power hardware: this model uses a CR2032 without the GLx model's solar panel. Its cast housing is IP67 and fog resistant, and it keeps the standard microdot footprint for replacement mounts.
Key Features
- ACSS CQB Multi-Reticle Select with four user-selectable modes
- 20mm clear aperture in a 5.0 oz, 2.8 in body
- 12 brightness settings, including 3 night vision settings
- AutoLive, low-battery indicator, and high/low setting indicator
- 0.5 MOA clicks with 100 MOA of windage and elevation travel
- Low mount and absolute cowitness mount with spacer included
- IP67 and fog-resistant cast housing
Pros
- +Four reticle modes let the shooter simplify the sight picture
- +100 MOA of travel in each axis gives more adjustment range than the MD-25 Gen 2
- +5.0 oz body is lighter and 2.8 in length is shorter than the MD-25 Gen 2
- +Three night vision settings provide one more low-light level than the MD-25 Gen 2
- +Standard microdot footprint supports replacement mount options
Cons
- −20mm aperture is five millimeters narrower than the MD-25 Gen 2
- −Only two included center heights versus four with the MD-25 Gen 2 mounting kit
- −Primary Arms publishes no runtime rating for this model
- −No solar backup, unlike the GLx MD-21s
Detailed Specifications
- Reticle
- Red ACSS CQB Multi-Reticle Select: all features, chevron plus BDC, chevron plus horseshoe, or chevron alone
- reticleControls
- Hold the plus or minus button for three seconds to cycle reticle modes
- reticleSubtensions
- Chevron outer tip span is approximately 5.7 MOA, inner tip span is approximately 4.3 MOA, and BDC dot diameter is approximately 1 MOA, derived from the manual's ranging references; no horseshoe MOA value is published
- bdcCalibration
- Six references from top to bottom are chevron tip, outer wing tips, bottom legs, then BDC dots 1, 2, and 3. Yardages: 5.56/5.45 with 100 yd zero, 100/200/300/400/500/600; .308, 6.5 Grendel, or 77gr 5.56 with 50 yd zero, 50/200/300/400/500/600; 300 BLK or 7.62x39 supersonic with 100 yd zero, 100/200/250/300/400/450; 300 BLK 200gr SMK subsonic with 50 yd zero, 50/no reference/75/100/125/150; 12 gauge 1 oz slug with 25 yd zero, 25/50/75/100/125/150; .22LR 40gr with 50 yd zero, 50/no reference/100/125/150/175; 7.62x54R zeroed 1/2 inch below point of impact at 100 yd, 100/200/300/400/500/600; 9mm carbine 115/124gr with 25 yd zero, 25/no reference/100/150/175/200; 10.5 inch 5.56 with 100 yd zero, 100/200/250/300/400/500. Load and barrel length variation may require tuning with the top BDC dot at extended distance
- rangingAndWind
- Chevron outer tips range an 18 inch target at 300 yards, inner tips range it at 400 yards, chevron edges mark 5 MPH wind holds for 400, 500, and 600 yards, and each BDC dot covers a 5 inch target at 500 yards. Vertical ranging for a 5 ft 10 in standing target uses the lowest BDC dot and marks 500, 600, and 0 to 400 yard bands, best used behind a magnifier
- shotgunReference
- Horseshoe approximates the pattern of 12 gauge 00 buckshot from an 18.5 to 20 inch barrel at 25 yards
- reticleManual
- https://www.primaryarms.com/core/media/media.nl?id=26414791&c=3901023&h=YkIGM0DnG-Xwcestwb4epCauPoHHMJefL-H-Sxn68BS3gOu
- Magnification
- 1x
- Battery Type
- CR2032 3V lithium coin
- brightnessSettings
- 12 levels, including 3 night vision settings
- activation
- AutoLive motion-activated illumination
- indicators
- Low-battery and high/low setting indicators
- Waterproof Rating
- IP67
- fogResistance
- Fog resistant
- weight
- 5.0 oz
- Length
- 2.8 in
- windowSize
- 20mm clear aperture
- Adjustment Type
- 0.5 MOA per click
- Adjustment Range
- 100 MOA elevation / 100 MOA windage
- Material
- Cast housing
- Mount Type
- Standard microdot footprint
- includedMountHeights
- 1.41 in and 1.535 in center heights
- color
- Black
- sku
- PA-SLX-MD-21-ACSS
- mpn
- 810028
- warranty
- Lifetime
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