Holosun 507K Footprint: K vs. RMSc and Verified Pistol Fits
The 507K uses the Holosun K footprint—not generic RMSc. See verified direct fits, required plates, known exclusions, and screw cautions.
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The Holosun 507K X2 uses the Holosun K footprint. Do not assume that every Shield RMSc cut accepts it: firearm makers distinguish K from RMSc, and the correct route can be direct, plate-mounted, or unsupported depending on the exact pistol and generation. Verified direct-fit examples include Glock Slimline MOS-K, the factory optic-ready SIG P365X/XL cut, S&W Shield Plus Optics Ready, Ruger MAX-9, Taurus GX4 T.O.R.O., FN Reflex MRD, H&K CC9, and IWI Masada Slim. Standard Glock 43X/48 MOS and Springfield Hellcat OSP require exact K adapter routes, while Smith & Wesson explicitly excludes the 507K from the Equalizer group.
The useful question is not simply “What footprint is the 507K?” It is: does the manufacturer of my exact pistol, slide, or adapter document a 507K route?
The Holosun HS507K-X2 product page calls the direct-mount interface K footprint. That gives the optic side of the connection. The pistol side still has to be established separately.
507K Footprint and Published Specifications
Holosun’s current product page publishes these buying and setup facts:
| Field | Manufacturer value |
|---|---|
| Direct-mount interface | Holosun K footprint |
| Body dimensions | 1.6 × 0.98 × 0.95 in |
| Window | 0.58 × 0.77 in |
| Weight | 1 oz |
| Reticle | Selectable 2-MOA dot, 32-MOA circle, or combined circle-dot |
| Adjustment | 1 MOA per click |
| Battery | Side-loading CR1632 |
| Included screws | Two M3x12 and two M4x12 |
The optic is open-emitter. Holosun publishes IP67 water resistance, 5000G vibration resistance, 12 brightness settings, and up to 50,000 hours of battery life. Those are manufacturer claims, not Optics Intel field-test results.
The included screws do not make every M3 or M4 installation correct. Thread pitch, usable engagement, head geometry, plate thickness, and clearance below the slide remain host-specific.
K vs. RMSc: The Safe Answer
Holosun K and Shield RMSc are related micro-optic interfaces, but they are not safe synonyms.
Glock’s official optic-mounting guide provides a particularly clear real-world boundary:
- standard Slimline MOS is identified as Shield RMSc and uses M4 screws;
- Slimline MOS-K is separately identified as accepting either Holosun K or RMSc without a plate and uses the optic maker’s M3 screws.
If “RMSc” automatically proved “507K direct fit,” Glock would not need that model-level distinction. The practical rule is therefore simple: a shared family resemblance is a lead; an exact manufacturer fitment statement closes the answer.
Manufacturer-Verified Direct Fits
These are not universal promises for every pistol bearing the family name. Each row is limited to the named optic-ready host and current source.
| Pistol or slide | 507K route | Evidence boundary |
|---|---|---|
| Glock 43X/48 MOS-K | Direct | Glock says MOS-K accepts Holosun K; identify MOSK in the case item number. Glock source |
| SIG P365X / P365-XL factory optic-ready cut | Direct | Holosun names P365X/XL; this does not extend to every P365-family slide. Holosun Canada source |
| S&W Shield Plus Optics Ready | Direct | S&W’s current fitment guide marks 407K/507K compatible for the Shield Plus group. S&W source |
| Ruger MAX-9 | Direct | Ruger’s manual names HS407K and HS507K and gives the locating-pin procedure for them. Ruger manual |
| Taurus GX4 T.O.R.O. | Direct | Taurus names HS407K/HS507K in its published optic list. Taurus source |
| FN Reflex MRD | Direct with FN hardware | FN names 407K/507K; its safety bulletin requires the correct FN-supplied screws. FN fit source · FN screw bulletin |
| H&K CC9 | Direct | H&K describes the cut as an “RMSc / 407K footprint.” The brochure does not name individual optics or provide optic-specific screw instructions. H&K brochure |
| IWI Masada Slim | Direct | IWI’s specification sheet names the 507K. IWI source |
Open the Fit Checker preselected for the 507K to inspect any one of these paths with its evidence attached.
Verified Adapter and Plate Routes
A plate route is not a lesser answer when the plate is purpose-built, the interfaces are identified, and the hardware stack is correct. It is simply a different mounting system.
| Host | Required route | What the source establishes |
|---|---|---|
| Standard Glock Gen4/Gen5 MOS 9mm | Holosun KPLT-MOS9MM | Holosun names 407K and 507K for Glock MOS-compatible 9mm slides. Holosun plate |
| Standard Glock 43X/48 Slimline MOS | Exact MOS-to-407K/507K plate | C&H names the host and both optics; Glock’s standard cut remains RMSc. C&H plate |
| Springfield Hellcat OSP / Hellcat Pro | Exact RMSc-to-K plate | C&H names Hellcat and 407K/507K; Springfield’s hardware limit still controls. C&H plate |
| S&W M&P M2.0 Optics Ready | C.O.R.E. Plate 2 | S&W maps 407K/507K to Plate 2. S&W source |
| Springfield XD-M / XD-M Elite OSP | XD OSP Plate 4 / XD507 | Springfield lists 407K and 507K for Plate 4. Springfield plate |
| Springfield 1911 DS Prodigy AOS | AOS Plate A12B | Springfield assigns Holosun K-series optics to A12B. Springfield AOS plate |
| CZ P-10 OR | CZ plate P9784-0015 | CZ’s corporate store names HS407K, HS507K, and EPS-series optics. CZ plate |
Do not replace an exact plate listing with “any RMSc-to-K plate.” The bottom interface must match the exact slide, the top must name the 507K or its documented K group, and the supplied screws must match the current plate revision.
A Documented No-Fit That Matters
Smith & Wesson’s current optic fitment guide marks the Holosun 507K not compatible with the Equalizer group, even though it lists the 507K for the Shield Plus group.
That exception is the best reason not to shop by footprint nickname. Two pistols can be discussed online as “RMSc class” while the manufacturer publishes different model-specific results. On the Equalizer, use S&W’s current table rather than transferring a Shield Plus answer.
Three Common Buying Mistakes
1. Treating every RMSc cut as a K cut
An RMSc label alone does not answer a 507K purchase. Require an exact pistol/optic statement or an exact adapter listing.
2. Confusing 507K with 507C
The 507K is the narrow K-footprint model. The 507C is a larger RMR-footprint optic. The similar name does not make their plates interchangeable.
3. Choosing screws from the optic box by diameter alone
Holosun includes M3x12 and M4x12 pairs, but the host determines which thread and usable length are correct. FN’s Reflex MRD bulletin is a concrete warning: FN requires the correct FN-supplied screw set and says incorrect screws can interfere with pistol function.
Installation Check Before Torque
Use the current manuals for the pistol, adapter, and optic. At minimum:
- Unload and clear the pistol, then follow its disassembly procedure.
- Identify the exact pistol SKU, generation, and optic cut.
- Confirm a direct-fit or adapter source that names the 507K/K route.
- Dry-fit the stack; the optic and plate must sit flat without rocking.
- Confirm thread, screw head, usable engagement, and clearance below the slide before applying thread treatment or torque.
- Follow the exact maker’s torque and retention instructions—never a number copied from a different pistol, plate, or cover screw.
- Function-check the unloaded pistol, witness-mark the fasteners, zero, and recheck them on the maker’s schedule.
If the maker publishes a maximum protrusion rule, that measured clearance controls. For example, Springfield limits Hellcat optic-screw protrusion to 0.095 inch / 2.4 mm, while FN publishes its own Reflex MRD screw and engagement requirements. These values are not interchangeable.
Where That Leaves You
- If the firearm maker names 507K or Holosun K, follow that exact direct or plate route.
- If it only says RMSc, keep researching; do not promote the result to “direct fit” from the footprint label alone.
- If an exact adapter maker names both your pistol and 507K, verify the current hardware stack and use that documented path.
- If the maker says not compatible, the negative model-specific statement overrides a generic footprint assumption.
For the three most-searched platforms, use the model-specific guides: 507K on Glock 43X/48 MOS, 507K on SIG P365, and 507K on Springfield Hellcat Pro.
Frequently Asked Questions
What footprint does the Holosun 507K use?
The HS507K-X2 uses the Holosun K footprint. Holosun lists K as its direct-mount interface and supplies M3x12 and M4x12 screw pairs, but those screws are only box contents—the firearm or plate maker still controls thread, usable length, and installation procedure.
Is the Holosun K footprint the same as Shield RMSc?
No—not as a purchasing rule. Glock describes its standard Slimline MOS as RMSc, then separately says MOS-K is modified to accept either K or RMSc. That manufacturer distinction is why an RMSc label alone does not prove a 507K direct fit.
Does a Holosun 507K fit a Glock 43X MOS without a plate?
It depends on the exact cut. Glock says standard Slimline MOS is RMSc, so use a G43X/48-MOS-to-407K/507K plate. A case item number ending MOSK identifies the newer factory cut that Glock says accepts K directly with the optic maker's M3 screws.
Does a Holosun 507K fit a Springfield Hellcat Pro without a plate?
No on the unmodified factory Springfield Micro cut. Use an exact Hellcat/Hellcat Pro-to-407K/507K adapter and verify assembled screw protrusion against Springfield's 0.095-inch / 2.4-mm maximum.
Does a Holosun 507K fit a SIG P365 without a plate?
Holosun explicitly names factory optic-ready P365X and P365-XL models as direct fits. That statement does not cover every base P365, XMacro, FUSE, AXG, SIG-LOC, replacement slide, or aftermarket cut, so identify the exact slide before buying.
Do the Holosun 407K and 507K use the same footprint?
Yes. Holosun classifies both as K-footprint optics, and its Glock MOS plate names both models. Their reticle systems differ, but a verified mounting path that explicitly names both 407K and 507K applies to either.