Holosun and Sig P365 Fitment Guide

Posted by Recoil Gunworks on Sep 18th 2025

Sig P365 & Holosun: The Ultimate Fitment Guide

1. The "Direct Fit" Models (No Plate Required)

These optics use the Holosun K-Series footprint, which matches the factory cut on the P365, P365XL, P365-XMACRO, and P365 Fuse perfectly.

  • Holosun 407K / 507K: The classic choice. Slim, reliable, and sits low enough to co-witness with many factory iron sights.

  • Holosun EPS Carry: This is currently the #1 recommendation for the P365. It is an enclosed emitter optic (the laser is protected by a second pane of glass).

    • Why it’s better: It prevents lint, dust, and rain from blocking the dot—essential for daily IWB carry.

  • Holosun SCS-Carry: The newest option. It is a solar-charging, enclosed optic that sits even lower, designed specifically to co-witness with standard-height irons.

2. The "Adapter Required" Models

If a customer wants to use a larger "Duty" optic from their full-sized gun on a P365, they will need an expansion plate.

  • Holosun 407C / 507C / 508T / 507 Comp: These use the larger RMR footprint.

    • The Fit: They are wider than the P365 slide. You will need a K-to-RMR adapter plate.

    • The Downside: This adds height, usually meaning you can no longer see your iron sights through the glass.

Specific Model Breakdown

P365 Variant Optics Footprint Recommended Holosun
P365 Fuse Shield RMSc / K-Series EPS Carry or 507K
P365-XMACRO Shield RMSc / K-Series EPS Carry or SCS-Carry
P365XL Shield RMSc / K-Series 507K or 407K
P365 (Standard) Non-Optics Ready Needs an Optics-Ready Slide or Milling
P365 AXG Legion Shield RMSc / K-Series EPS Carry (Matches the premium feel)

3 Pro-Tips for P365 Mounting

1. The Screw Length Warning

Sig P365 slides have the extractor spring channel located directly under the right-side optic screw hole.

  • The Fix: Always use the screws provided by Holosun specifically labeled for the P365. If the screw is too long, it will pinch the extractor spring, causing your gun to fail to extract (FTE).

2. Co-Witnessing with Iron Sights

On the P365 Fuse and X-Macro, the EPS Carry and 507K typically allow for a "lower 1/3 co-witness." This means you can still see the tips of your metal sights through the bottom of the glass as a backup.

3. Red vs. Green Reticle

For the P365, Green dots (e.g., HE507K-GR) are increasingly popular. The human eye picks up green faster in daylight, which is helpful on a small concealed carry gun where speed is everything.