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

This Apex Optic Mount lets you put a Holosun 509T on your SIG P320 with the SIG-LOC optic cut. It’s built for shooters who want a solid, reliable mount without extra fluff. The mount is machined from a single billet of steel with a Black Oxide finish, so it holds up to regular use and keeps the optic tight on the slide.

Works on the P320 Legion, M17, M18, and other P320 models that have the factory SIG-LOC cut. The integrated rear sight sits in front of the optic and does double duty as a gas shield. That means less carbon and debris hitting your optic lens, so you spend less time cleaning and more time shooting. The rear sight is set to co-witness in the bottom 25% of the optic window, giving you a usable backup sight picture without blocking your view.

A tall front sight is included with the mount to get that co-witness right. You get two sight height options depending on your barrel length—pick the one that fits your setup. If you want the rear sight behind the optic instead, that version comes with a blast deflector block in front that you can’t see through the optic. Both versions keep your glass cleaner.

This mount also works with the M17/M18 factory Loaded Chamber Indicator, so no extra mods needed. The screws have a thread locking patch pre-applied—torque them to 20 in-lb and you’re good to go. The sights are regulated for POA=POI at 10 yards with 115 grain ammo, which is a common range load.

Key specs and fitment:

• Designed for Holosun 509T on SIG P320 with SIG-LOC optic cut
• Fits P320 Legion, M17, M18, and other SIG-LOC P320 models
• Machined from billet steel with Black Oxide finish
• Integrated rear sight in front of optic acts as gas shield
• Rear sight co-witnesses in bottom 25% of optic window
• Tall front sight included (choose height based on barrel length)
• Gas shield keeps optic objective lens cleaner
• Thread locking patch pre-applied to screws (torque to 20 in-lb)
• Sights regulated for POA=POI at 10 yards with 115 Gr. ammunition
• Works with factory Loaded Chamber Indicator on M17/M18
• No rear sight installation needed—integrated into mount

If you don’t need backup iron sights, check out the Apex 112-018-PRO version.