Does the Holosun 507K X2 fit the Taurus GX4 TORO / GX4XL?
Yes — it mounts straight to the slide with no adapter plate, so the optic is the only part to buy.
Direct mount — cross-compatible
The slide's native pattern is Shield RMSc, but this footprint is cross-compatible with it and mounts with no adapter. A subset of RMSc: K optics drop onto RMSc cuts, but a K-only cut has no rear posts for an RMSc optic to index on. Screw thread differs from Shield's M4 — check what shipped in the box.
Will your iron sights co-witness?With standard-height irons: No co-witness. Standard-height irons sit far below any pistol red dot window and stay usable only with the optic removed. Suppressor-height sights are the fix for that, not a different optic.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.
How this slide mounts an opticMilled for the RMSc pattern, so Shield RMSc and Holosun K optics bolt straight on with no plate. Taurus lists exactly one adapter for this slide, for the Trijicon RMRcc, and states plainly that an RMRcc will only work on the GX4 T.O.R.O. through it. That is worth reading twice: the RMRcc looks like a small RMR, is not one, and is not an RMSc either.
What to order, and how to fit it
The fit checker's build sheet for this pair, written for iron sights of unknown
height.
Open it in the
fit checker to set your sights, work out a safe screw length from
your own caliper readings, or copy it as text.
Build sheet
Data compiled September 2026 · Optic Mounting
Pistol
Taurus GX4 TORO / GX4XL
Optic
Holosun 507K X2
Footprint
Holosun K
Slide
Taurus GX4 T.O.R.O. direct cut
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. Under about 0.290 in and it will not co-witness.
Suppressor-height sights — if yours are standardOptional — for a co-witness. Third-party: Trijicon, Ameriglo, XS, Dawson
Fasteners — which bag
You are not buying these. Screws will arrive with the pistol, with the optic and with the plate, and they look alike. The tapped thread is in the slide or the plate — the optic only has a clearance hole — so the host decides the thread, not the optic.
Joint
Thread
Comes from
Optic → slide
#6-32
Supplied with the optic. A direct cut is the easy case: no plate in the stack, so the screws that came with the optic are normally correct. The cover-plate screws from the pistol are not optic screws — set them aside.
On the bench before you start
Torque wrench — covering 15 in-lb — a 10–50 in-lb driver covers most of this work
Driver bits — T10 — the bit must seat fully or it will round the head
Calipers — for the screw length check below; guessing is how screws end up in the striker channel
Blue removable threadlocker — Vibra-Tite VC-3 or Loctite 242. Never red.
Degreaser — isopropyl or brake cleaner — oil under a plate is why plates move
Witness-mark paint or lacquer — so later movement is visible before it costs you a zero
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. This matters more than people think.
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 — the screw 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
A screw that is too long bottoms out on the slide or intrudes into the striker channel; one that is too short strips under recoil. This sheet gives you the thread — it cannot give you the length, because that depends on your exact plate and optic stack. Test-fit dry and count threads.
Sight co-witness
Depends on your front sight height, which varies by SKU and production run even within one model name. With standard-height irons: no co-witness. With suppressor-height irons: normally a lower-third co-witness on a direct cut.
Confirm the firearm is unloaded before any work on the slide. Mounting an optic is gunsmithing — work 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 compiled September 2026, for comparing routes rather than budgeting to the dollar. Torque and fitment figures are compiled from manufacturer documentation — confirm against the current manuals for your pistol, optic and plate before installing. Not affiliated with or endorsed by any manufacturer.
Something on this page wrong?Say what it should be. Corrections from someone who owns the pistol are why
this is worth more than a spec sheet — and nothing here changes without a source, so bring one.