Primary Arms GLx MD-21s ACSS CQB
A 20mm push-button microdot with four selectable ACSS CQB reticle modes, AutoLive, and a top-mounted solar failsafe.
- Price
- $230
- Weight
- 5 oz
- Brand
- Primary Arms
- Category
- Optics
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 with top-mounted solar failsafe backup
- •12 brightness settings, including 3 night vision settings
- •5.0 oz, 2.8 in long, cast housing
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Primary Arms GLx MD-21s Push Button 21mm Red Dot Sight with AutoLive - ACSS CQB Reticle
Primary Arms GLx MD-21S Micro Reflex Red Dot Sight 1x ACSS-CQB Red Dot Reticle Black
Price History
90-day low $229.99 · at low nowMore optics guides & articles
Guides
Overview
The GLx MD-21s is the solar-equipped member of the MD-21 pair. Its top-mounted panel backs up the CR2032, while AutoLive wakes the reticle on motion and a low-battery indicator warns before the coin cell is exhausted. The 20mm aperture, 5.0 oz weight, and 2.8 inch length match the SLx MD-21, so the solar failsafe is the functional hardware difference between them.
Push buttons control 12 brightness settings, including three for night vision, and switch the ACSS CQB between four modes. Hold either button for three seconds to cycle among all features, chevron plus BDC, chevron plus horseshoe, and chevron alone. This lets the same open horseshoe, precision chevron, and three-dot drop ladder serve close work or present a cleaner aiming picture without changing the optic's zero.
Each click moves 0.5 MOA, and the optic provides 100 MOA of elevation plus 100 MOA of windage travel, nearly twice the published adjustment range of the MD-25 Gen 2. The cast, IP67, fog-resistant housing adds a fully multi-coated anti-reflective lens. Its low mount and absolute cowitness mount with spacer provide 1.41 and 1.535 inch center heights on the standard microdot footprint.
Key Features
- ACSS CQB Multi-Reticle Select with four user-selectable modes
- Top-mounted solar failsafe backs up the CR2032 battery
- 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, fog-resistant cast housing with fully multi-coated anti-reflective lens
Pros
- +Solar panel provides a backup power source beyond the CR2032
- +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
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
- −The solar panel is the only hardware upgrade over the otherwise identical SLx MD-21
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=26414765&c=3901023&h=E9lETBsNOYq8tK2CQiOeTxTKFkMBIeIdG814ktZsso-XYuRT
- Magnification
- 1x
- Battery Type
- CR2032 3V lithium coin with top-mounted solar failsafe backup
- 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
- lensCoating
- Fully multi-coated anti-reflective lens
- 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-GLX-MD-21S-ACSS
- mpn
- 810026
- warranty
- Lifetime
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