SIG SAUER Custom Works P320 Gold Fire Control Unit

The SIG SAUER Custom Works P320 Fire Control Unit gives experienced P320 owners a serialized foundation for a personalized modular pistol. This exact gold-finished FCU is manufacturer part number 8900160 with UPC 798681633319. It features a titanium-nitride finish and a matching skeletonized flat trigger and is intended for use with compatible post-upgrade P320 components.

The serialized core of a P320

On the P320 platform, the fire control unit is the serialized component legally treated as the firearm. It contains the internal chassis, trigger, sear, slide catch, and related fire-control parts. Because the FCU is removable from the grip module, one serialized unit can serve as the center of a properly configured P320 assembled from compatible grip modules, slides, barrels, recoil assemblies, and magazines.

This product is an FCU only. It does not include a grip module, slide, barrel, recoil spring, sights, magazine, takedown lever, optic, or complete pistol. Those parts must be selected separately and must be mutually compatible with the desired caliber, slide length, grip size, and magazine format.

Custom Works finish and flat trigger

The chassis and skeletonized flat trigger use a gold-colored titanium-nitride finish that distinguishes this Custom Works unit from a standard black P320 FCU. Titanium nitride provides a hard, low-friction surface and gives the unit its characteristic appearance. The flat trigger face offers a broad, consistent contact point and a more linear feel as the finger moves through the trigger press.

The FCU does not have a manual thumb safety. Users should never assume that changing external modules alters the basic safety rules or the function of the internal fire-control system. Installation, inspection, and any parts replacement should follow SIG SAUER instructions and be performed by a qualified armorer or gunsmith when appropriate.

Compatible P320 configurations

SIG SAUER lists this FCU for compatible post-upgrade P320 components in 9mm Luger, .357 SIG, and .40 S&W. The chosen slide, barrel, recoil assembly, grip module, and magazine determine the final configuration and caliber. Not every P320-branded component works with every other part, and caliber-conversion combinations can require specific slide and magazine dimensions.

Before purchasing a build kit, confirm compatibility with MPN 8900160 and verify that every component is designed for a post-upgrade P320. This FCU is not described as compatible with .45 ACP P320 components. It is also not a P365 FCU and does not fit P365-series grip modules or slides.

Key features

• Factory SIG SAUER Custom Works P320 fire control unit
• Serialized component requiring an FFL transfer
• Gold-colored titanium-nitride finish
• Titanium-nitride skeletonized flat trigger
• No manual thumb safety
• For compatible post-upgrade P320 components
• Supports properly configured 9mm, .357 SIG, or .40 S&W builds
• FCU only; external pistol components are sold separately

Transfer and assembly considerations

Because the FCU is the serialized firearm, it must be transferred through a Federal Firearms Licensee and is subject to all applicable federal, state, and local restrictions. The purchaser should confirm eligibility and transfer requirements before ordering. Final assembly should be function-checked without ammunition, and the completed pistol should be inspected for correct parts fit, safe trigger operation, proper slide movement, and reliable magazine engagement before live fire.

Confirm the package label shows MPN 8900160 and UPC 798681633319. Keep all ammunition away from the work area during assembly or maintenance, follow the current P320 owner’s manual, and use only components approved for the intended configuration.