Apex Optic Mount for Holosun 509T to Sig P320 RX PRO Cut

Description

This Apex Optic Mount solves the specific problem of attaching a Holosun 509T to a Sig Sauer P320 slide that has the factory RX Pro cut. Instead of buying a new slide or using bulky adapter plates that raise your optic too high, this direct-fit mount keeps the 509T low and secure.

Built for Arizona Conditions
Machined from a single billet of steel, then treated with a black oxide finish, this mount handles the heat, dust, and grit of the desert. Steel resists deformation better than aluminum when your slide gets hot from holster draw practice or extended strings of fire. The black oxide finish sheds carbon and wipes clean easily — no flaking or chipping.

Low Bore Axis, Clear Backup Sights
The mount indexes the 509T directly into the RX Pro cut, keeping the optic as close to the bore as possible. This reduces the shift in your point of impact when shooting from unconventional positions or with a suppressor mounted. Your factory iron sights (including the loaded chamber indicator) remain fully visible through the optic window.

Fitment Details

• Slide Compatibility: Sig Sauer P320 with factory RX Pro cut. Directly replaces the factory optic cover plate.
• Also Fits: Sig M17, M18, and Legion models that use the RX Pro slide cut pattern.
• Loaded Chamber Indicator: Retains full function of the factory LCI. No modification needed.
• Optic Compatibility: Holosun 509T (all versions, including X2 and RD models).
• Mounting Hardware: Uses the same screws as your factory RX Pro plate. Torque to manufacturer specs.

Why This Works for Your P320
The P320 platform already gives you a modular fire control unit and reliable performance under dust. This mount preserves those advantages. You get a solid, repeatable zero — even after removing and reinstalling the optic — because the steel-to-steel interface doesn’t compress or shift over time.

Price: $65
At this price point, you’re not paying for a “name” — you’re paying for precision machining, a durable finish, and a design that solves the specific gap between the Holosun 509T footprint and the Sig RX Pro cut. No adapters, no shims, no guesswork.

In the Desert, Steel Matters
Aluminum mounts expand faster than steel in direct sun. That can cause zero shift. The steel billet construction here maintains dimensional stability from