Sig Sauer P365 Frame Fire Control Unit Custom Blk

The Sig Sauer P365 Fire Control Unit Custom in Black is the serialized foundation for building a personalized P365 pistol tailored to your carry method, hand fit, and shooting preferences. As the regulated core component of any P365 build, this FCU lets you start from the inside out—selecting your grip module, slide, barrel, optics, and accessories around a single controlled piece. Whether you're a P365 owner looking to create a dedicated second configuration, an armorer assembling custom defensive pistols, or an enthusiast who wants maximum flexibility in a micro-compact platform, this Custom Works FCU gives you the modular starting point to do it.

The Custom Works finish and flat trigger face set this FCU apart from standard internal assemblies. The flat trigger encourages consistent finger placement for more repeatable trigger control, while the refined black finish provides a premium foundation for your build. The modular P365 ecosystem is one of the platform's greatest strengths—one serialized FCU can support compact carry setups, XL configurations, longer slide assemblies for range work, and even optics-ready or compensated builds when paired with compatible components.

This FCU is compatible with 9mm Luger and .380 ACP P365 configurations, depending on the parts you select for your build. Because the fire control unit is the federally regulated component, acquiring one requires an FFL transfer, but it opens the door to assembling a pistol that matches your exact specifications without starting with a complete handgun and replacing major components.

Key Features

• Serialized fire control unit—the regulated core of your P365 build
• Flat trigger face for improved shooter interface and finger placement consistency
• Custom Works refined black finish for a premium aesthetic
• Compatible with 9mm Luger and .380 ACP P365 configurations
• Modular design supports compact, XL, optics-ready, and compensated configurations
• Enables dedicated second builds without purchasing a complete pistol

Specifications

Frequently Asked Questions

What is a fire control unit and why would I need one?

The fire control unit is the federally regulated component of a firearm. By acquiring a serialized P365 FCU, you own the regulated core and can build the rest of the pistol around it—choosing grip size, slide length, barrel, and optics to match your needs. This approach gives experienced builders and P365 owners the flexibility to create a second or custom configuration without purchasing an entire new pistol.

What P365 configurations can I build with this FCU?

This FCU is compatible with the broad P365 ecosystem, including compact carry modules, XL grip modules, longer-slide range configurations, optics-ready slides, and compensated setups. The specific configuration depends on the compatible grip modules, slides, barrels, and other components you select for your build.

Does this FCU work with 9mm and .380 ACP?

This FCU is compatible with both 9mm Luger and .380 ACP P365 configurations when paired with appropriate compatible parts. The caliber compatibility depends on the slide, barrel, and magazine components you choose for your build.

What's included and what will I need to complete a build?

The FCU is a stripped component—the serialized core only. To complete a functional P365, you'll need to source a compatible grip module, slide, barrel, spring assembly, and magazines. This modular approach lets you customize every aspect of your finished pistol.