Sig P320 Fitment Guide: Compact & Full-Size Slides, Barrels & Recoil Springs
Posted by Fdez Werx on 27th Oct 2026
This guide covers Fdez Werx Sig Sauer P320 fitment: Comp'd Compact and Full-Size slides, barrels, recoil spring assemblies, optic notes, OEM small parts, and send-in porting. Use it with the P320 charts on our FAQ compatibility page before you order so barrel length and RSA match the slide.
All Fdez Werx P320 parts are drop-in fit.
The P320 Fire Control Unit (FCU) is modular. Fdez Werx Comp'd Compact and Full-Size slides mount on P320 FCUs and grip modules as noted below. Grip interchange is not the same as a recommended barrel / RSA setup — match barrel length and RSA to the slide.
1. Quick Fit Rules
- Grip fit: X5 slides use X5 grips but can also fit Full-Size grips. Full-Size slides fit Full-Size, Carry, or Compact grips. X-Carry, Carry, and Compact slides fit X-Carry, Carry, Compact, or Subcompact grips.
Recessed fit: an OEM Full-Size slide on an X5 grip, a Compact, Carry, or X-Carry slide on a Full-Size grip, or a Subcompact or XCompact slide on a Carry, X-Carry, or Compact grip will work, but the slide sits recessed on the dust cover instead of flush with the end. The Fdez Werx Comp'd Full-Size slide is X5 length overall because of its integral comp, so it fits X5 grips flush. - Small parts: all P320 small parts interchange between every variant, except the trigger bar, which is specific to manual-safety or non-manual-safety pistols.
- Model by model: the X5 must use X5 barrels and X5 recoil springs. The XFull uses Full-Size 4.7" barrels and Full-Size recoil spring assemblies. The Carry uses 3.9" Compact barrels and Compact recoil spring assemblies. The Subcompact and XCompact (now discontinued by Sig) use 3.6" barrels and Subcompact recoil spring assemblies.
- Integral comp slides: Fdez Werx P320 slides with an integral compensator cannot take a longer barrel than the one listed for that slide (4.7" for the Full-Size, 3.6" for the Compact).
- Optic footprint: Fdez Werx P320 slides use an RMR-style optic footprint only.
- AXG, Legion, and X-Series grips: these names describe grip material, not a different fit. AXG is aluminum, Legion is tungsten-infused polymer, and X-Series is polymer. Slide fitment follows the grip size (Full-Size, Compact, Carry, and so on).
- X5 barrels and recoil springs do not fit Full-Size slides. Full-Size slides take 4.7" Full-Size barrels and Full-Size recoil springs.
- Full-Size slides take 4.7" full-size barrels: Fdez Werx ported 4.7" P320 barrels, or any flush-and-crown 4.7" P320 barrel.
- Compact (P320C) slides take 3.6" barrels: any flush-and-crown 3.6" barrel, or Fdez Werx ported 3.6" barrels (coming soon, no ETA).
- Full-Size slides use P320 full-size recoil spring assemblies — not X5 recoil spring assemblies.
- Compact (P320C) slides use P320C / compact recoil spring assemblies.
- Full-size adjustable RSA spring weights are 12 / 14 / 15 / 16 lb.
- Threaded barrels are not recommended in Fdez Comp'd Compact or Full-Size slides (per product listings).
- Slides ship stripped unless you select installed add-ons on the product page.
2. Slide Fitment Matrix
Both Fdez Werx P320 slides use an integral recessed expansion chamber compensator, a dedicated rear dovetail separate from the optic cut, and an RMR-style optic footprint. Finish is DLC Black unless a Cerakote option is selected on the listing (custom Cerakote is currently paused through November 2026).
| Fdez Werx Slide | Barrel | RSA | Grip notes (FAQ) | Shop |
|---|---|---|---|---|
| Comp'd P320 Compact 0.175" longer than a standard 3.6" Compact slide | 3.6" flush & crown, or Fdez 3.6" ported (coming soon). Not recommended for threaded barrels. | 9mm 3.9" Compact or X-Carry recoil spring assembly. Not an X5 RSA. | X-Carry, Carry, Compact, or Subcompact grip modules. | Shop |
| Comp'd P320 Full-Size | 4.7" flush & crown, or Fdez 4.7" ported. Not recommended for threaded barrels. | P320 full-size RSA (std or tungsten adjustable). Not X5. | Full-Size, Carry, or Compact grip modules. Also fits X5 grips; the integral comp makes it X5 length overall. | Shop |
Holsters (from listings): Compact — X-Compact or open-ended full-size holsters; Full-Size — X5 or open-ended full-size holsters. Adjustable retention recommended. Best with standard 124–147 gr ammunition; +P works but may reduce recoil control.
3. Barrel Fit / Does Not Fit
| Barrel | Fits | Does not fit / notes | Shop |
|---|---|---|---|
| 4.7" Non-LCI Ported | Fdez Werx P320 Full-Size slides only (per listing). Non-LCI profile; flush & crowned muzzle; 9mm. | Not for Compact / P320C slides. Use only with a matching Full-Size ported window. | Shop |
| 4.7" Flush & Crown (any) | Fdez Werx P320 Full-Size slides | Fdez does not currently list a dedicated 4.7" flush & crown barrel — use a compatible third-party / OEM-spec 4.7" flush & crown barrel | — |
| 3.6" Flush & Crown (any) | Fdez Werx P320 Compact / P320C slides | Not a Full-Size 4.7" substitute. Fdez does not currently list a dedicated 3.6" flush & crown barrel | — |
| 3.6" Fdez Ported | Fdez Werx P320 Compact / P320C slides (when available) | Coming soon (no ETA / no live product page yet) | Coming soon |
Safety: Match port geometry to the slide’s expansion chamber / top window. A ported barrel in a non-ported window (or the wrong length) can send gas and debris in unsafe directions.
4. Recoil Spring Assemblies
| RSA | Fits | Spring weights / notes | Shop |
|---|---|---|---|
| Full-Size 4.7" Adjustable RSA (stainless guide rod) | P320 Full-Size 4.7" (Fdez Comp'd Full-Size). Not X5. | Flatwire; 12 / 14 / 15 / 16 lb (Green / Yellow / Orange / Red) | Shop |
| Full-Size 4.7" Tungsten Adjustable RSA | P320 Full-Size 4.7". Not X5. | Tungsten guide rod; 12 / 14 / 15 / 16 lb (same set as the standard Full-Size adjustable RSA) | Shop |
| Compact Adjustable RSA | Listing: P320 Compact (3.9"). Fits the Fdez Comp'd Compact slide (9mm). | Flatwire; 12 / 14 / 16 / 18 / 20 lb (Green / Yellow / Orange / Red / Blue) | Shop |
| OEM Compact / Carry RSA | Listing: P320 Compact and Carry / XCarry with 3.9" barrel. Compact slide listing offers this as the Compact / X-Carry add-on RSA. | Factory-style OEM assembly | Shop |
| OEM Subcompact / XCompact RSA | Listing: P320 Subcompact and XCompact with 3.6" barrel | Not for the Fdez Comp'd Compact slide, which uses a 3.9" Compact or X-Carry RSA | Shop |
Do not put an X5 RSA in a Fdez P320 Full-Size slide. Match RSA length / model to the slide: full-size RSA for Full-Size, compact RSA for Compact / P320C.
5. Optic Cut & Screws
| Item | Fit / notes | Shop |
|---|---|---|
| Fdez Comp'd Compact & Full-Size optic cut | RMR-style footprint only (no SIG-LOK or RMSc cut). Cover plate and optic screws available as a slide add-on. | Full-Size / Compact |
| P320 Full-Size RMR optic screws (FAQ) | FAQ: 4-40 x 5/16 for P320 Full-Size slides with RMR optic mount | FAQ |
6. Completing a Build & OEM Small Parts
Typical stripped-slide build: Fdez slide + matching barrel + matching RSA + P320 Slide Completion Kit + correct optic screws / cover plate. The completion kit includes extractor, extractor pin, extractor spring, extractor spring pin, striker group assembly, and rear slide cap (barrel, sights, and RSA not included). Listing fit: P320, M17, M18 (9mm / 357 SIG).
| Part | Notes | Shop |
|---|---|---|
| P320 9/357 Slide Completion Kit | Genuine Sig factory parts to complete a stripped slide | Shop |
| Extractor / pin / spring; striker; slide catch; mag release; takedown lever; sear housing; trigger bar | OEM-spec P320 small parts stocked for builds and service; see each listing for exact model notes | Browse OEM Parts |
| Align Tactical OFFSET Extended Mag Release (RH) | Listing: does not fit AXG, XTEN, .45 ACP, or subcompact modules with shorter mag catches | Shop |
| AXG G10 grip panels (Black / Red Lava) | OEM AXG grip panels; see listings for fit | Black / Red Lava |
7. Porting Service
| Service | Fits | Notes | Shop |
|---|---|---|---|
| P320 Porting Service | Customer-supplied P320 slide and barrel | Slide & barrel porting, back-boring, deburring, front sight dovetail relocation, disassembly/reassembly. Do not include the serialized FCU. Lead time about 7–10 business days (1–2 weeks) from when we receive your item, plus shipping. Custom Cerakote is paused through November 2026 (you may still send items in). | Shop |
Ship stripped slide and barrel with your order number to: Fdez Werx, 6012 Bayfield Pkwy Ste 134, Concord NC 28027.
8. FAQ
Can I use an X5 recoil spring in a Fdez Full-Size slide?
No. Full-Size slides use P320 full-size recoil spring assemblies, not X5 RSAs.
What barrel does the Comp'd Compact take?
3.6" flush-and-crown barrels, or Fdez Werx 3.6" ported barrels when they are available (coming soon). Threaded barrels are not recommended.
What barrel does the Comp'd Full-Size take?
4.7" flush-and-crown barrels, or the Fdez Werx 4.7" Non-LCI ported barrel. Threaded barrels are not recommended.
What optic cut do Fdez P320 slides use?
RMR. FAQ lists 4-40 x 5/16 screws for P320 Full-Size RMR mounts.
Are Fdez P320 slides sold complete?
No. They ship stripped unless you select installed add-ons (sights, cover plate, completion kit, barrel, RSA) on the product page.
Browse P320 Slides, P320 Barrels, Performance Parts, OEM Parts, and Custom Services, or see the charts on the FAQ.