American Defense Holosun 509T QR Lower 1/3 Co-Witness Quick Release Mount

The American Defense Holosun 509T QR lower 1/3 co-witness quick release mount pairs precision engineering with practical shootability for AR pistol builds and other compact weapon platforms. This one-piece mount is machined from 6061 T6 aluminum and finished in hard coat T3 mil-spec anodize—a finish that stands up to hard use in the field. The quick-release design lets you dismount your optic fast when you need to, and the lower 1/3 co-witness height positions your Holosun 509T red dot for a sight picture that coexists naturally with iron sights if you run them.

The standout feature here is American Defense's patented QD Auto Lock Lever system, which accommodates both in-spec and out-of-spec rail systems—a real advantage if you're running a build with looser tolerances or unconventional platforms. You won't need proprietary tools to dial in your setup: the lever adjusts with your finger or a flat blade screwdriver, and you can configure it to lock toward the front or rear of the rail depending on your preference. The clamping surface is engineered to maximize engagement with your rail, so your optic stays planted when it counts.

Whether you're building a duty-grade AR pistol, a short-barrel rifle, or any platform where you want a compact red dot solution that's quick on and off the gun, this mount delivers the kind of no-fuss reliability that separates good gear from the rest.

Key Features

• One-piece 6061 T6 aluminum construction with hard coat T3 mil-spec anodize
• Patented QD Auto Lock Lever system handles both in-spec and out-of-spec rails
• Lower 1/3 co-witness height for iron sight compatibility
• Quick-release design for rapid optic removal
• Tool-free adjustment—finger or flat blade screwdriver only
• Configurable lever lock position (front or rear)
• Superior rail clamping surface for maximum engagement

Specifications

Frequently Asked Questions

Will this mount work on any rail system?

The American Defense QD Auto Lock Lever system is designed to accommodate both in-spec and out-of-spec rail systems, giving you compatibility across a wider range of platforms than mounts with tighter tolerances.

Can I use this with iron sights?

Yes. The lower 1/3 co-witness height positions the Holosun 509T so it coexists with standard iron sights on your upper receiver.

Do I need special tools to adjust or remove the mount?

No. The lever adjusts with just your finger or a flat blade screwdriver, and the quick-release design lets you remove the optic without tools.

What's the finish like—will it hold up in the field?

The mount is finished in hard coat T3 mil-spec anodize, a durable coating designed to withstand regular use and environmental exposure.