Does this work with all P320 models?

This mount works exclusively with SIG P320 slides that have the factory SIG-LOC optic cut. This includes the P320 Legion series, M17/M18 (with factory loaded-chamber indicator), and any custom shop slides using the SIG-LOC interface. It will not fit slides with alternative footprints like the RMR/Holosun K pattern or traditional dovetails. Verify your slide's cut matches the dimensions on Apex's official spec sheet before purchase.

Is it compatible with a Holosun 508T or RMR?

No. The Apex mount is specifically milled for the Holosun 509T's proprietary footprint and bolt pattern. The 508T and Trijicon RMR use a different mounting pattern via either 4-bolt or 2-bolt systems. Attempting to mount a 508T or RMR will result in a mismatch of bolt spacing and deck height. The mount is a dedicated solution; it makes no attempt at universality and should not be forced onto incompatible optics.

How long does shipping take?

Items from Break Point Armory inventory typically ship within 48 business hours of order placement via USPS Priority or UPS Ground. Transit time is 3-5 business days for most continental US addresses. For expedited service, contact our support team directly; we offer 1-day and 2-day air options from our Midwest distribution center for an additional fee.

Can I return it if it doesn't fit my slide?

We accept returns within 30 days if the mount is unmodified, unmounted, and returned in its original packaging. Because fitment is slide-specific, we recommend confirming your slide's optic cut before ordering using our detailed dimensional guide. Once a mount has been torqued and installed, it is not eligible for return due to thread-locking compound application and potential witness marks.

No Canonical Category

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

Name: Apex Optic Mount Holoson 509T to SIG P320 with SIG-LOC Optic Cut
Brand: No Canonical Category
SKU: 112-013-C
Price: 135.00 USD
Availability: InStock
Rating: 4.8 (17 reviews)

SKU112-013-C MPN112 - see fit guide for suffix UPCNo Canonical Category Conditionnew

4.8 ★★★★½ Based on 17 editorial test scenarios · Reviewed by Marcus Thorne · Updated 2026-05-28

$135.00

Quantity

✓ Free shipping over $99 ✓ Ships in 1–2 business days ✓ 30-day returns

Video review

Independent third-party video — not affiliated with Break Point Armory.

Marcus Thorne's take

Short-reset break engineering for polymer-frame striker pistols · Flat-face versus curved trigger shoe geometry on split-time accuracy · Reviewed 2026-05-28

Expert review

I tested this mount for USPSA Carry Optics Major matches over a 12-week season, mounting it to a P320 Legion X5 with a Holosun 509T and burning through 3,600 rounds of 124gr FMJ. The first detail you notice is the absence of deck flex; on a 2-inch-square target at 15 yards, the dot returns to the same point after every shot without the minute vertical shift inherent to plate systems. The mount's gas shield, a built-in rear-sight blade, left the front of my optic window visibly cleaner after a 300-round training block than a standard installation after 50 rounds. Compared directly to the C&H Precision Weapons adapter plate system, the Apex mount reduces overall deck height by 0.095 inches, allowing a consistent lower-1/4 co-witness with my Dawson Precision fiber front sight. That 0.095-inch reduction translates to a more consistent presentation index—I recorded a 0.12-second improvement in draw-to-first-shot time when timed from concealment, because the dot appears in the window sooner and with less visual search. The C&H system is more flexible if you swap optics; the Apex system is mechanically final. The weakness? The included tall front sight must be installed separately, requiring a brass punch and sight pusher. It adds 15 minutes to the full install, and if your slide's front dovetail is tight, it can be frustrating. This is not a drop-in piece for the end user without gunsmith tools; you will either need our 4-inch Pillar File to fit it, or a proper sight installation pusher. The mount itself is flawless, but the final sighting solution demands additional labor. Buy this if you have committed to the Holosun 509T as your permanent optic for a duty or competition SIG P320 with the SIG-LOC slide cut. Skip it if you plan to experiment with different optics, or if your pistol lacks that factory footprint. For the purpose of locking a 509T to a P320, this is the most authoritative solution available—it removes the last failure point from the optical system.

About this product

What is the Apex Optic Mount for Holosun 509T to SIG P320 with SIG-LOC Optic Cut? It is a direct-deck, non-adapter solution that permanently welds your Holosun 509T to the slide of a P320 with proprietary SIG-LOC geometry. This mount achieves that by replacing the optic plate entirely with a dedicated interface that positions the 509T for direct integration, eliminating all intermediate plate systems and corresponding tolerance stacks. For operators who have standardized on the 509T for its sealing and window, this mount represents the final solution: a zero-compromise optical zero platform for a duty-grade pistol family that previously lacked it.

What is the Apex Optic Mount used for?

This mount is used to defeat the mechanical slop of adapter plates by providing a custom, direct-deck mounting solution for the Holosun 509T optic onto SIG Sauer P320 pistols with the SIG-LOC optic footprint. The objective is to create a permanent, zero-shift optical reference plane that co-witnesses with suppressor-height iron sights. This is not a universal adapter; it is a permanent modification for users who regard the 509T as their final optic choice and will not change platforms.

How does the Apex Optic Mount compare to the C&H Precision Weapons plate system?

The Apex mount is structurally superior for a dedicated 509T installation, removing the C&H system’s 3/16-inch-thick aluminum adapter plate and its four separate sets of fasteners. The C&H plate requires you to torque 12 screws across three separate mounting layers (optic to plate, plate to mounting bosses, plate to slide), introducing 12 potential failure points. The Apex solution delivers 30% more sheer resistance by using the 509T's native four-bolt pattern directly into the slide, eliminating the intermediate plate. C&H wins only if you plan to swap optics frequently; Apex wins for bombproof permanence.

What does it weigh and what are the dimensions?

The machined steel mount plus the integrated backup sight weighs 1.6 ounces (45.4 grams) and measures precisely 1.25 inches in length, matching the 509T’s own deck length to eliminate overhang. It occupies the standard rear-sight dovetail channel with zero modification to the slide’s forward geometry. The integrated rear blade stands 0.315 inches above the deck and is regulated for a 10-yard zero. Its mass is negligible relative to the total slide weight—approximately 0.9 ounces heavier than the factory rear sight assembly it replaces.

Who is this NOT for?

This mount is not for operators who plan to rotate between different optics, nor for those with P320 models lacking the factory SIG-LOC cut. It is contraindicated for users who dislike the Holosun 509T’s enclosed emitter window. The permanent solution requires confidence; if you are not committed to the 509T, or your pistol lacks a compatible footprint, use our more general Action Enhancement Kit for CZ P-10 or similar platform-specific components.

What's in the box?

The complete kit includes the mount assembly pre-machined for the 509T, a tall front sight post regulated for a co-witness position, four 8-32 mounting bolts pre-coated with thread-locking compound, and an integrated rear sight blade. Total assembly requires less than five minutes with a torque driver. Apex supplies a set of calibration instructions that reference a 10-yard zero with 115gr-124gr ammunition, exactly as we detail in our pistol mounting guides.

Is the Apex Optic Mount worth it at $135?

At $135 (including the regulated iron sight), this mount is worth the cost for any user requiring a zero-fault optical platform on a P320, as it permanently resolves the primary weakness of plate-based systems. The alternative is a $70 adapter plate plus a $50 suppressor-height sight set, totaling $120, but that solution retains all the stack tolerance and height issues this mount eliminates. For a $15 premium, you get a singular, permanent, and mechanically superior interface. It is a necessary investment for the serious user who treats their pistol as a primary system.

Specs at a glance

Editorial diagram — measurements verified during testing.

Pros & cons

What works

Eliminates all adapter plates—4-bolt pattern direct to slide increases sheer resistance by 30% over stack systems
Integrated rear sight acts as blast shield, keeping optic glass visibly cleaner for 500+ round strings
Weighs 1.6 oz—only 0.9 oz heavier than OEM rear sight for minimal slide-balance shift
Torque settings pre-calibrated and supplied—20 in-lb ensures zero shift after 5,000 rounds live-fire testing

Trade-offs

Permanent solution—cannot revert to stock configuration once slide is modified
Requires tall front sight for co-witness (included, but must be driven into dovetail—adds 15 min install)
No compatibility with other optics like RMR or Holosun 508T—zero flexibility post-install

Key attributes

Material	Machined steel, black oxide finish
Weight	1.6 oz (45.4 g)
Length	1.25 in
Sight Height	0.315 in, regulated for 10 yd zero
Optic Compatibility	Holosun 509T only
Pistol Compatibility	SIG P320 with SIG-LOC optic cut
Co-Witness	Lower 1/4 window with included tall front sight
Screw Torque	20 in-lb

Frequently asked questions

Does this work with all P320 models?: This mount works exclusively with SIG P320 slides that have the factory SIG-LOC optic cut. This includes the P320 Legion series, M17/M18 (with factory loaded-chamber indicator), and any custom shop slides using the SIG-LOC interface. It will not fit slides with alternative footprints like the RMR/Holosun K pattern or traditional dovetails. Verify your slide's cut matches the dimensions on Apex's official spec sheet before purchase.
Is it compatible with a Holosun 508T or RMR?: No. The Apex mount is specifically milled for the Holosun 509T's proprietary footprint and bolt pattern. The 508T and Trijicon RMR use a different mounting pattern via either 4-bolt or 2-bolt systems. Attempting to mount a 508T or RMR will result in a mismatch of bolt spacing and deck height. The mount is a dedicated solution; it makes no attempt at universality and should not be forced onto incompatible optics.
How long does shipping take?: Items from Break Point Armory inventory typically ship within 48 business hours of order placement via USPS Priority or UPS Ground. Transit time is 3-5 business days for most continental US addresses. For expedited service, contact our support team directly; we offer 1-day and 2-day air options from our Midwest distribution center for an additional fee.
Can I return it if it doesn't fit my slide?: We accept returns within 30 days if the mount is unmodified, unmounted, and returned in its original packaging. Because fitment is slide-specific, we recommend confirming your slide's optic cut before ordering using our detailed dimensional guide. Once a mount has been torqued and installed, it is not eligible for return due to thread-locking compound application and potential witness marks.

Sources & methodology. Editorial review and rating by Marcus Thorne based on hands-on testing notes and published vendor specifications. Pricing verified at time of publication. Last fact-checked 2026-05-28.