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

Steel Optic Mount – Holosun 509T to Sig P320 RX PRO Cut

This optic mount adapts the Holosun 509T footprint to Sig Sauer P320 slides cut with the factory RX PRO pattern. Machined from billet steel with a black oxide finish, it replaces the need for adapter plates that add height or introduce flex. The mount directly interfaces with the slide’s existing screw holes and uses the factory rear sight dovetail area without blocking the loaded chamber indicator (LCI). For shooters running a 509T on an RX PRO-cut slide, this component provides a rigid, direct-mount solution that maintains a lower optic deck height than plate adapters.

Compatibility

• Sig Sauer P320 slides with factory RX PRO cut (e.g., X-Five Legion, X-Carry, X-Compact RX PRO models)
• Sig Sauer M17 / M18 slides with RX PRO cut
• Sig Sauer P320 Legion series slides (RX PRO pattern)
• Works with factory loaded chamber indicator (LCI) – no modification required
• Holosun 509T (all variants – standard, X2, GR)

Key Features

• Material: Billet steel, black oxide finish
• Direct-mount design – no adapter plate needed
• Preserves factory LCI function
• Lower optic deck height vs. plate adapters
• Includes necessary mounting screws (verify thread pitch for your slide generation)

Install Difficulty: 2 / 5

Tools needed: Torque driver (in-lb), blue Loctite, #6 or T10 bit (depending on screw head). Remove factory rear sight if present (some RX PRO slides ship without rear sight). Apply Loctite to screws, torque to 12–15 in-lb per screw. No slide milling required.

FAQ

Will this mount work on a standard P320 slide without the RX PRO cut?

No. This mount is designed specifically for slides already cut with the Sig RX PRO pattern. It does not adapt to standard dovetail or non-RX PRO slides.

Does it include screws for the Holosun 509T?

The mount includes screws for attaching to the slide. Screws for securing the 509T to the mount are typically included with the optic. Verify screw length if using aftermarket fasteners.

Will this mount affect iron sight co-witness?

The mount occupies the rear sight dovetail area. Most RX PRO-cut slides do not retain a rear sight when using a direct-mount optic. Plan for suppressor-height front sight if you require a co-witness.

Shipping & Warranty: Ships within one business day. Covered by manufacturer warranty against material or workmanship defects. Return policy applies to unmodified, resalable condition within 30 days of delivery.