Primary Arms MD‑21 Red Dot Test | Solar vs Standard Options

Published on December 14, 2025
Duration: 9:40

This guide covers the installation and zeroing of Primary Arms MD-21 (SLx) and MD-21S (GLx) red dot sights. It details selecting mounts, attaching the optic, powering on, and adjusting for zero using 0.5 MOA clicks. The guide emphasizes safety and highlights features like the ACSS-CQB reticle and solar power option on the GLx model. Instruction is provided by experienced gear reviewers from Elliott Delp's channel.

Quick Summary

The Primary Arms MD-21S (GLx) red dot sight is recommended over the MD-21 (SLx) due to its integrated solar panel for extended battery life and the advanced ACSS-CQB reticle, which offers multiple aiming points for various ranges. Both models feature 12 illumination settings, including 3 NVG-compatible modes, and use the Aimpoint Micro footprint for mounting versatility.

Chapters

  1. 00:00Introduction: MD-21/MD-21S Overview
  2. 01:57GLx vs SLx Features: Solar Power
  3. 03:37Technical Specifications: Dot & Illumination
  4. 04:10ACSS-CQB Reticle System Explained
  5. 05:57Adjustments and Battery Compartment
  6. 06:51Mounting and Footprint Compatibility
  7. 08:34Final Verdict and Recommendation

Frequently Asked Questions

What are the key differences between the Primary Arms MD-21 (SLx) and MD-21S (GLx) red dot sights?

The MD-21S (GLx) features a solar panel for extended battery life and the advanced ACSS-CQB reticle, while the MD-21 (SLx) is a more basic model without solar power and a simpler 2 MOA dot, making the GLx model the recommended choice for its enhanced features.

Does the Primary Arms MD-21 red dot sight have night vision compatibility?

Yes, both the MD-21 (SLx) and MD-21S (GLx) models offer 12 illumination settings, including three specifically designed to be compatible with night vision devices, enhancing their usability in low-light tactical scenarios.

What is the reticle system on the Primary Arms MD-21S (GLx)?

The MD-21S (GLx) features the ACSS-CQB reticle, which offers multiple aiming points including a central chevron, Bullet Drop Compensator (BDC) holds for various ranges, and a horseshoe, allowing for rapid target acquisition and precise aiming.

What is the mounting footprint of the Primary Arms MD-21 red dot sights?

The Primary Arms MD-21 and MD-21S red dot sights utilize the standard Aimpoint Micro footprint. This ensures broad compatibility with a wide array of aftermarket mounts, allowing users to easily integrate the optic with different rifle platforms.

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