American Defense Holosun 509T QR Mount Lower 1/3 Co-Witness
American Defense Mfg.
$113.69
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American Defense Mfg.
American Defense Holosun 509T QR Mount Lower 1/3 Co-Witness
The American Defense Mfg. AD-509T QR Lower 1/3 Mount is a precision-engineered quick-release optic mount purpose-built for the Holosun 509T red dot, delivering rock-solid performance on AR pistols and other compact weapon platforms without adding unnecessary bulk or weight.
- Patented QD Auto Lock Lever ensures fast, repeatable attachment and detachment
- Lower 1/3 co-witness height for seamless use with standard iron sights
- Precision machined from aircraft-grade 6061-T6 aluminum for maximum strength
- Hard coat T3 Mil-Spec anodize finish resists corrosion, wear, and harsh conditions
- Tool-free adjustment — configurable with a finger or flat-blade screwdriver
- Lever mounts front or rear to suit your preferred shooting setup and hand orientation
Who This Is For
This mount is ideal for AR pistol owners, competition shooters, and tactical users who run the Holosun 509T and demand a lightweight, no-compromise mounting solution. If you frequently transition between firearms or need to remove your optic for transport and storage, the quick-detach lever system lets you return to zero reliably every time — making it equally valuable for home defense builds and range use alike.
Specifications
| Brand | American Defense Mfg. |
|---|---|
| Model | AD-509T QR Lower 1/3 |
| Compatible Optic | Holosun 509T |
| Mount Height | Lower 1/3 Co-Witness |
| Material | 6061-T6 Aluminum |
| Finish | Hard Coat T3 Mil-Spec Anodize |
| Attachment System | Patented QD Auto Lock Lever |
| Rail Compatibility | MIL-STD-1913 Picatinny (in-spec & out-of-spec) |
| Tool Requirement | None (finger or flat-blade screwdriver) |
| Lever Orientation | Front or Rear Configurable |
| Construction | One-Piece Unit |
| Country of Origin | USA |
Frequently Asked Questions
Will this mount work on any AR-15 or AR pistol Picatinny rail?
Yes. The AD-509T QR mount is designed to fit MIL-STD-1913 Picatinny rails and is specifically engineered with American Defense's Patented QD Auto Lock Lever to accommodate both in-spec and out-of-spec rail systems. This makes it compatible with a wide range of AR pistols, AR-15 rifles, and other platforms equipped with a standard Picatinny top rail.
Does this mount return to zero after being removed and reattached?
Absolutely. American Defense Mfg. mounts are renowned in the industry for their return-to-zero performance. The superior clamping surface and Auto Lock Lever system provide consistent, repeatable engagement with the rail, so your Holosun 509T zero is maintained each time you remount — a critical feature for any duty or defensive application.
What is the difference between lower 1/3 co-witness and absolute co-witness?
Lower 1/3 co-witness means your backup iron sights (BUIS) will appear in the lower third of the Holosun 509T's viewing window, keeping the red dot centered and unobstructed during normal use while still allowing you to verify iron sight alignment. Absolute co-witness places the irons directly at the center of the optic window. Lower 1/3 is the more popular choice for AR-platform shooters who want a clean primary dot picture with irons available as a backup.
