The American Defense AD-509T is a quick-detach rifle mount purpose-built for optics using the Holosun 509T footprint — this version at lower 1/3 co-witness height, raising the dot so iron sights appear in the lower third of the window. ADM's patented Auto Lock QD lever attaches and removes the optic fast while holding a secure, repeatable return-to-zero on Picatinny rails.
Machined from 6061-T6 aluminium with a Type III hardcoat anodised finish. Made in the USA.
Height: Lower 1/3 Co-Witness — also available in Low Mount and Absolute Co-Witness.
How It Compares
Running an AEMS optic instead? See the AD-AEMS mount. Browse all red dot mounts and enclosed red dots; read our co-witness heights guide.
Ideal For
- Holosun 509T optics on rifles/carbines
- Lower 1/3 co-witness AR setups
- Quick-detach with return-to-zero
Key Features
- Purpose-built for Holosun 509T footprint
- Lower 1/3 co-witness height
- ADM Auto Lock quick-detach lever; return-to-zero
- 6061-T6 aluminium, Type III hardcoat; ~2.3 oz; USA-made
Technical Specifications
| Fits |
Holosun 509T footprint |
| Mount |
Picatinny (Auto Lock QD) |
| Height |
Lower 1/3 co-witness |
| Material |
6061-T6, Type III hardcoat |
| Weight |
~2.3 oz |
| MPN / UPC |
AD-509T-11-STD / 810008517642 |
What's Included
- American Defense AD-509T QD mount (lower 1/3 co-witness), mounting hardware
UK Delivery & Support
UK-stocked and dispatched tracked from our UK warehouse — no import duties or customs delays — backed by UK-based support and ADM's lifetime warranty.
Frequently Asked Questions
Which optics fit?
Optics using the Holosun 509T footprint (e.g. HE509T / HS509T).
What does lower 1/3 co-witness mean?
The optic sits slightly higher than the irons, so they appear in the lower third of the window for a cleaner sight picture.
Does it return to zero?
Yes — the Auto Lock QD lever gives repeatable return-to-zero.
