AM DEF HOLOSUN 509T CO-WITNESS

Description

The American Defense Manufacturing AD-509T-10-STD is a quick-detach mount built specifically for the Holosun 509T footprint, aimed at shooters who want a repeatable, zero-returning attachment point for that optic on a flat-top AR-pattern rifle. The co-witness mount height centers the optic at 1.4 inches, which places the 509T’s reticle in line with standard-height iron sights so backup sights remain usable through the optic window without any holdover adjustment.

ADM’s QD lever system is the defining design choice here. Rather than threading a fastener down against a Picatinny rail, the lever clamps across the rail’s cross-slots and releases with a single motion, letting you pull the optic off and remount it without tools while returning to the same zero. This matters most when you’re moving an optic between hosts or need to swap to a magnifier setup and back. The standard lever on this variant — as opposed to ADM’s Tactical lever configuration — is the legacy-style release familiar to anyone who has used earlier ADM mounts.

The mount is manufactured by American Defense Mfg in New Berlin, Wisconsin. The 509T-specific design accounts for that optic’s footprint geometry, so it is not interchangeable with Holosun models that use a different footprint, such as the ACSS Vulcan variant of the 509T. If your irons are at standard AR height, this co-witness configuration gives you a direct, uncompromised sight picture without the optical center-line penalty that comes with lower-profile mounting options.