Home / Pistols / SIG Sauer P365-XMACRO / XMACRO Comp / Holosun 507K X2

Does the Holosun 507K X2 fit the SIG Sauer P365-XMACRO / XMACRO Comp?

Yes. It mounts straight to the slide with no adapter plate; the optic is the only part to buy.

Direct mount — cross-compatible

The slide is cut for Shield RMSc, and this footprint fits that cut with no adapter.

Same answer forThe Holosun 507K X2 goes on the SIG Sauer P365 Optics Ready, SIG Sauer P365X and SIG Sauer P365XL the same way: they share this slide's optic cut.

SlideSIG P365 optic cut (RMSc pattern)

Optic footprintHolosun K

Optic screwsM3 × 0.5 or M4 × 0.7, by slide · T10

Optic torque15 in-lb

Cost to mount$300–450

New to red dots? What footprint, plate, co-witness and the rest mean →

Which screwsSIG tapped early P365 optic cuts M3 × 0.5 and later ones M4 × 0.7, and sells a screw set for each. The model name doesn't tell you which slide you have; SIG's screw-set page shows both. Your slide is tapped M3 or M4. To tell which, turn an M3 screw in by hand only: if it catches and runs in smoothly, the slide is M3; if it wobbles and never bites, the slide is M4. Never put a driver on a screw that won't start by hand. The Holosun 507K X2 box holds M3 and M4 screws. Both are in the box, so this is a matter of picking the right pair, not buying any. Source: SIG Sauer, ROMEO-X M4 screw set ↗; SIG Sauer, ROMEO-X M3 & M4 screw kit ↗; Holosun, HS507K-X2 (in the box: 2× M3×12, 2× M4×12) ↗.

Will your iron sights co-witness?With standard-height irons: No co-witness. Standard-height irons sit well below any pistol red dot window and are only usable with the optic off. Suppressor-height sights fix that; a different optic won't.With suppressor-height irons: Co-witnesses. A ≈0.290–0.315 in front sight normally sits in the lower third of the window on a direct cut. Mounted directly, the optic sits as low as the cut allows, the best case for a co-witness. This optic's window runs small (19.5 × 14.7 mm), so a front sight slightly off the ideal height is more likely to miss it. That's the typical case for this kind of optic, not a guarantee: pistols don't standardize sight and optic heights the way rifles do.

How this slide mounts an opticMilled for the Shield RMSc pattern. No plate is needed. Holosun K optics bolt on directly as well. P365 SIG-LOC slides are a different cut, listed separately.

GuidesShield RMSc vs Holosun K: which optic fits which cut · Suppressor-height sights: will your irons co-witness? · Red dot lost zero? Troubleshooting the mount

What to order, and how to fit it

The fit checker's build sheet for this pair, assuming sights of unknown height. Open it in the fit checker to set your sights, work out screw length from your own caliper readings, or copy it as text.

Rather not do it yourself? Mounting an optic is a short bench job for most gun shops and gunsmiths. Buy the parts under "Parts to order" and take this sheet with you.

Build sheet

Data compiled September 2026 · Optic Mounting

Pistol: SIG Sauer P365-XMACRO / XMACRO Comp
Optic: Holosun 507K X2
Footprint: Holosun K
Slide: SIG P365 optic cut (RMSc pattern)
Mount: Direct mount — cross-compatible

Parts to order

1 ×	Holosun 507K X2Holosun K footprint · 2 MOA + 32 MOA circle	$300–450
1 set	Suppressor-height sights, if yours are standardMeasure your front sight first, then compare it with the sight heights published for this slide and optic, where the sheet lists them. The height that co-witnesses depends on the slide and the optic; a slim slide needs less than a full-size one.	optional
	Estimated total: optic only	$300–450

Where to buy

Holosun 507K X2Holosun K footprint	Holosun — this item ↗
Suppressor-height sights, if yours are standardOptional, for a co-witness. Makers include Trijicon, Ameriglo, XS and Dawson

Fasteners: which bag

You don't buy these. Screws come with the pistol, the optic and the plate, and they look alike. The thread is tapped into the slide or plate (the optic only has a clearance hole), so they decide the thread, not the optic.

Joint	Thread	Comes from
Optic → slide	M3 × 0.5 or M4 × 0.7, by slide	Supplied with the optic: use the pair that matches your slide. The slide's tapping decides the screw, not the optic. Start each screw by hand.Thread trapSIG tapped early P365 optic cuts M3 × 0.5 and later ones M4 × 0.7, and sells a screw set for each. The model name doesn't tell you which slide you have; SIG's screw-set page shows both. Your slide is tapped M3 or M4. To tell which, turn an M3 screw in by hand only: if it catches and runs in smoothly, the slide is M3; if it wobbles and never bites, the slide is M4. Never put a driver on a screw that won't start by hand. The Holosun 507K X2 box holds M3 and M4 screws. Both are in the box, so this is a matter of picking the right pair, not buying any.

On the bench before you start

Torque wrench — covering 15 in-lb (a 10–50 in-lb driver covers most jobs)
Driver bits — T10, fully seated so they don't round the head
Calipers — for the screw length check below
Blue removable threadlocker — Vibra-Tite VC-3 or Loctite 242. Never red.
Degreaser — isopropyl or brake cleaner
Witness-mark paint or lacquer — so you can see if anything moves later

Install spec

Optic torque15 in-lb

ScrewsM3 × 0.5 or M4 × 0.7, by slide

DriverT10

Interface2 screws, 2 forward lugs (rear posts omitted)

Sequence

Clear the pistol. Drop the magazine, lock the slide back, look and feel the chamber, then do it again.
Remove the cover plate and set it aside with its screws.
Degrease the slide cut and the optic base.
Seat the optic on the slide's recoil lugs and check it sits flat with no rock.
Fit the optic screws with blue threadlocker and torque to spec, alternating between them.
Let the threadlocker cure before firing (check the bottle; usually a few hours to overnight).
Confirm zero at your working distance, then re-check torque after the first 100–200 rounds.

Before you fire it

Screw length checked dry: it must not bottom out on the slide or reach the striker channel.
Optic sits flat with no rock, and the screws pulled up evenly.
Torque set with a wrench, not by feel. Witness-mark the screws so movement is visible later.
Threadlocker cured.
Function check, then zero confirmed live.

Screw length is the one that hurts

Too long and a screw bottoms out on the slide or reaches the striker channel; too short and it strips under recoil. This sheet gives the thread but can't give the length, which depends on your exact plate and optic stack. Test-fit dry and count threads.

Sight co-witness

Answered above: co-witness with standard and suppressor-height irons.

Confirm the firearm is unloaded before any work on the slide. Mounting an optic is gunsmithing: stay within your competence and use a gunsmith when a job is past it. Provided as-is with no warranty; you use this at your own risk. Prices are approximate street-price bands from September 2026. Torque and fitment figures come from manufacturer documentation; confirm against the current manuals for your pistol, optic and plate before installing. Not affiliated with or endorsed by any manufacturer.

The SIG Sauer P365-XMACRO / XMACRO Comp with other optics

Every optic on the SIG Sauer P365-XMACRO / XMACRO Comp, and how each mounts →

The Holosun 507K X2 on other pistols

Every pistol the Holosun 507K X2 fits →

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