# Do Shield RMSc and Holosun K optics share a footprint?

**Verdict: It depends**

Only partly. The screw pattern matches, the locating posts often do not — and Holosun names its own pattern K rather than RMSc for that reason.

They are treated as the same footprint constantly and Holosun does not call them the same thing. Its own product pages name the pattern "K Footprint" and list fitment as direct mount to that, not to RMSc. Shield originated RMSc, and the two are close enough that the screws line up — which is exactly what makes this look settled when it is not.

The screws are the part that matches. What varies is everything holding the optic against recoil. RMSc-pattern slides differ in how many locating posts they machine and where, and a K optic has recesses for its own arrangement rather than for all of them. So the same optic can seat properly on one RMSc-cut pistol and stand off the posts on another.

- **Screw spacing** — Matches — which is why it bolts on either way
- **Locating posts** — Vary by slide; the K recesses do not cover every arrangement
- **SIG P365 (RMSc cut)** — Holosun 407K and 507K seat directly
- **Glock 43X / 48 MOS (RMSc pattern)** — Four posts — an adapter plate is sold specifically for this pairing

That the two pistols above disagree is the whole answer. Both slides are described as RMSc and they are machined differently, so "RMSc" names a family of cuts rather than one cut. A K optic fitting your friend’s P365 tells you nothing about your 43X.

> **Caution:** Check the slide rather than the footprint name. Take the cover plate off and count the locating posts — that, not the label in the listing, is what decides whether an optic seats. Screws alone were never meant to carry recoil.

## Sources

- [Holosun HS507K-X2 — named as K Footprint, not RMSc](https://www.holosun.com/products/hs507k-x2)
- [Shield Sights — the originator of the RMSc pattern](https://www.shieldsights.com/)
- [An adapter plate sold for Glock 43X/48 MOS to Holosun 407K/507K](https://chpws.com/product/glock-43x-48-mos-to-holosun-407k-507k-adapter-plate/)

## More on optics and mounting

- [Will a Holosun 507K fit a Glock 43X MOS?](https://www.tactgpt.app/answers/holosun-507k-glock-43x-mos.md)
- [What red dot fits a SIG P365 without an adapter plate?](https://www.tactgpt.app/answers/sig-p365-red-dot-footprint.md)
- [Does a Trijicon SRO fit an RMR cut?](https://www.tactgpt.app/answers/trijicon-sro-rmr-same-footprint.md)

---

Last checked 2026-09-03. TactGPT can make mistakes. Always check important info for accuracy. The information it provides is intended for educational purposes only. It does not give legal advice; verify any laws cited. Always follow all applicable laws and safety guidelines.

[Ask TactGPT a different question](https://www.tactgpt.app/app/signup)