Holosun 407K / 507K Footprint Guide
Introduction
The Holosun 407K and 507K are among the most popular micro red dot sights for concealed carry pistols. They are widely used on compact and slimline handguns due to their small size, durability, and excellent battery life.
However, one of the most confusing topics for users is their mounting footprint compatibility.
This guide explains exactly what footprint the 407K/507K uses, which pistols support it, and how it compares to other common standards like RMSc and RMR.
What Footprint Do Holosun 407K and 507K Use?
The Holosun 407K and 507K use what is commonly called the:
π βHolosun K Footprintβ
This footprint is:
- Based on the Shield RMSc pattern
- Slightly modified for Holosun optics
- Designed for compact pistol slides
In most real-world applications:
The Holosun K footprint is considered compatible with RMSc footprint slides, but not always 100% identical depending on recoil lug design.
Holosun K vs RMSc Footprint (Important Difference)
Although often grouped together, there are subtle differences:
RMSc Footprint (Shield Standard)
- 4 recoil posts (corners)
- Wider compatibility across many pistol brands
- Used on micro-compact slides
Holosun K Footprint (407K / 507K)
- Based on RMSc pattern
- Slightly modified front lug geometry
- Rear lug configuration differs depending on slide design
Key takeaway:
- β Most RMSc slides support 407K / 507K
- β Some RMSc slides require minor adaptation or specific screw/lug compatibility
- β RMR footprint is NOT compatible
What Optics Use the 407K / 507K Footprint?
The Holosun K footprint is used by:
- Holosun 407K
- Holosun 507K
- Holosun EPS Carry series
- Other micro compact Holosun optics
These are designed for:
- Concealed carry pistols
- Slim slide platforms
- Lightweight optic setups
Compatible Pistol Platforms
The 407K / 507K footprint is commonly found on:
Direct-fit or near-direct-fit platforms:
- Sig P365 / P365 XL / P365 X Macro
- Springfield Hellcat OSP
- Glock 43X MOS / Glock 48 MOS
- Smith & Wesson Shield Plus
- Other RMSc-cut micro pistols
These pistols are designed for compact optics and often support RMSc/K footprint optics directly.
Can You Mount 407K / 507K on RMR Slides?
β No (Not Directly Compatible)
The RMR footprint is a full-size optic standard and:
- Uses different screw spacing
- Has different recoil lug positions
- Is physically larger
Options if you want to use it:
- Adapter plate (raises optic height)
- Slide milling (custom solution)
However, for compact pistols, this is generally not recommended.
Why the Holosun K Footprint Exists
Holosun designed the K footprint to:
- Fit smaller concealed carry pistols
- Maintain durability while reducing size
- Improve compatibility with RMSc ecosystem
- Offer better recoil lug stability than older micro patterns
Common Compatibility Mistakes
β Assuming RMSc = always perfect fit
Some RMSc slides need screw or lug adjustments.
β Confusing RMR and RMSc footprints
They are completely different systems.
β Using full-size optics on micro slides
507C / RMR optics are not for this footprint.
Best Use Cases for 407K / 507K Optics
These optics are ideal for:
- Everyday concealed carry (EDC)
- Compact defensive pistols
- Lightweight optic setups
- Low-profile slide builds
Summary
The Holosun 407K and 507K use the Holosun K footprint, which is based on the RMSc standard but with slight modifications.
Quick compatibility rule:
- β RMSc slides β usually compatible
- β Micro compact pistols β ideal match
- β RMR footprint β not compatible
Related Guides
To learn more about optic compatibility, you may also read:
- What Is RMSc Footprint
- RMR vs RMSc: Differences Explained
- Glock MOS Optic Compatibility Guide
- Sig P365 X Macro Optics Guide
Final Thoughts
The Holosun 407K / 507K footprint is one of the most widely used micro optic standards in the concealed carry market.
Understanding its relationship with RMSc helps you avoid mounting issues and choose the right optic for your pistol.
