Sig Sauer P320 Custom Works Fire Control 9mm .40 S&w .357 Sig Nitride Finish

The Sig Sauer 8900161 P320 Custom Works Fire Control Unit is an FFL-only firearm component that brings the P320's modular philosophy into the hands of builders, gunsmiths, and competitive shooters who want a high-performance drop-in trigger group for 9mm Luger, .40 S&W, or .357 Sig conversions. As part of the P320 series, this Custom Works FCU pairs a titanium frame for reduced weight and corrosion resistance with a black nitride finish for durable wear resistance, while the flat face skeletonized trigger delivers a consistent finger pad engagement and a crisp, repeatable break that benefits rapid-fire stages, defensive drills, and precision dry-fire practice. Designed to fit Sig P320 parts and frames, the unit simplifies caliber and configuration changes without altering the pistol's serialized core, making it ideal for custom builds, duty platforms, and modular carry systems where trigger feel and component longevity matter. If you're outfitting a semi-auto pistol for competition, range work, or tailored defensive carry, this Sig Sauer P320 Custom Works FCU offers the modern metallurgy, ergonomic trigger geometry, and compatibility that experienced shooters demand.