AM DEF HOLOSUN 509T QR LOWER 1/3

Description

The AD-509T mount exists for one specific job: putting a Holosun 509T on an AR pistol or similarly compact platform without adding unnecessary bulk or height. American Defense Manufacturing built it as a one-piece unit, which eliminates the flex and potential shift points that come with multi-piece designs. The body is precision machined from 6061-T6 aluminum and finished in Type 3 Mil-Spec hard coat anodize — a finish hard enough to resist the kind of contact wear a mount sees cycling on and off different builds over years of use.

This particular configuration sits at lower one-third co-witness height, meaning the 509T’s dot will appear in the upper portion of a standard AR iron sight picture rather than stacking directly on top of the irons. That keeps your dot-to-target sight picture clean while still leaving iron sights available without removing the optic. Whether that height works for your setup depends on your irons and stock — it is worth confirming before ordering.

The core mechanical feature is ADM’s patented QD Auto Lock Lever, which is designed to seat and release from a Picatinny rail quickly and repeatably without tools. The lever adjusts with a finger or a flat blade screwdriver and can be configured to lock toward the front or rear of the mount, accommodating different shooting preferences or clearance constraints. It is also adjustable enough to grip both in-spec and out-of-spec rail sections, which matters on budget or aftermarket rail systems that may not hold tight Picatinny tolerances. The clamping surface is machined to maximize contact with the rail, which is where repeatable zero retention actually comes from.