Apex Optic Mount Holoson 509T to SIG P320 with SIG-LOC Optic Cut

Description

This Apex Optic Mount provides a dedicated mounting solution for the Holosun 509T on Sig Sauer P320 pistols equipped with the SIG-LOC optic cut. It is built specifically for shooters who demand zero-compromise reliability on their duty rigs, competition guns, or serious carry builds.

Machined from billet steel with a Black Oxide finish, this mount is designed to hold zero under hard use. The integrated rear sight sits forward of the optic, functioning as a gas shield that deflects carbon and debris away from the objective lens. This keeps your glass cleaner for longer strings of fire, reducing the need to wipe the lens during a stage or after a training session. The sight also eliminates the extra step and cost of installing a separate rear sight.

The integrated rear sight is set for a lower 25% co-witness within the optic window, giving you a clear sight picture without cluttering the view. A tall front sight is included with the mount, and two height options are available depending on your barrel length—select the correct option at checkout for proper point of impact. Sights are regulated for POA=POI at 10 yards with 115 grain ammunition.

Key Specifications & Fitment:

• Designed for Sig Sauer P320 models with the SIG-LOC optic cut, including the P320 Legion, M17, and M18
• Compatible with factory Loaded Chamber Indicator on M17/M18 slides
• Includes thread locking patch pre-applied to mounting screws (torque to 20 in-lb)
• Two sight height packages available—choose based on barrel length
• Also available without backup iron sights: Apex 112-018-PRO

BUIS Configuration Options:

• Front-of-optic version: The base of the BUIS serves as the gas shield, protecting the lens from blast debris
• Behind-optic version: A dedicated blast deflector block sits in front of the optic, not visible through the glass

This mount is built for shooters who need their optic to stay functional round after round, whether on a competition timer or in a serious-use firearm. It mounts directly to the slide with no adapter plates, keeping the optic low and secure. The steel construction and integrated gas shield are practical upgrades that reduce maintenance and improve reliability in dirty conditions.