Sig P365, X-Macro & Fuse Slide & Ported Barrel Compatibility Guide (3.1" vs. 3.7" vs. 4.3")
Posted by Fdez Werx on 23rd Oct 2026
Because the Sig Sauer P365 Fire Control Unit (FCU) is completely modular, any Fdez Werx P365 slide will mount onto any P365, P365X, P365XL, X-Macro, or Fuse grip module. However, matching the right barrel length (3.1", 3.7", or 4.3"), porting style, and recoil spring assembly (RSA) to your specific slide is critical for safe, reliable cycling. Use the reference guide below before ordering your slide or barrel.
1. P365 Slide-to-Barrel & Recoil Spring Compatibility Matrix
| Fdez Werx Slide Model | Required Barrel Length & Type | Required Recoil Spring (RSA) | Optic Footprint |
|---|---|---|---|
| Comp'd P365 Macro / XL 3.0 Slide | 3.7" XL 3.0 Ported / Non-Ported | XL / X-Macro RSA (Standard or Tungsten) | RMSc (407K / 507K / EPS / Romeo-X) |
| Comp'd P365 XL ACCS Slide | 3.7" XL 3.0 / ACCS Ported | XL / X-Macro RSA (Standard or Tungsten) | RMSc or SIG-LOC |
| 365RS Comp'd P365 XL 3.7" Slide | 3.7" XL 3.0 / ACCS Ported | XL / X-Macro RSA (Standard or Tungsten) | RMSc or SIG-LOC |
| P365 FUSE 4.3" Slide | 4.3" Fuse Ported or 4.3" Non-Ported | Fuse 4.3" RSA (Standard or Tungsten) | RMSc or SIG-LOC |
| P365 FUSE ACCS 4.3" Slide & 365RS Fuse 4.3" Slide | 4.3" Fuse Chunk Port, 4.3" Ported, or 3.7" Non-Ported (comp'd) | Fuse 4.3" RSA (Standard or Tungsten) | RMSc or SIG-LOC |
2. Important Ported Barrel Safety Rules
- Match Port Geometry on 3.7" & 4.3" Barrels: The 3.7" XL 3.0 / ACCS Top-Ported Barrel aligns with XL 3.0, ACCS, and 365RS 3.7" top windows, whereas the 3.7" V-Ported Barrel is built for V-ported XL 3.0 slides and the 4.3" Chunk Port Barrel aligns with the Fuse ACCS and 365RS Fuse chunk port.
3. Completing Your P365 Build
All Fdez Werx slides are machined in-house in Concord, NC from U.S. 416R hardened stainless steel and ship stripped unless you select installed add-ons on the product page. To finish a build, pair your slide with a genuine Sig Sauer P365 Slide Completion Kit, M3 x 0.5 - 10mm Optic Screws, and our P365 Macro EDC Magwell and Aluminum Magazine Base Plates. Browse all P365 Slides and P365 Barrels.