“Sig P320 FCU” refers to the Fire Control Unit (FCU) of the SIG Sauer P320 pistol. The SIG Sauer P320 is a modular handgun that has gained popularity for its versatility and adaptability. The Fire Control Unit is a critical component of the P320, and it serves as the pistol’s serialized firearm component, which means it is legally considered the firearm.
The FCU or Fire Control Unit is the serialized assembly that holds the trigger components, controls, and slide rails.
Previously, shooters wanting to change their FCU had to spend time and money using a Dremel tool or risk modifying their pistol with an aftermarket kit.
The Sig P320 FCU includes various safety features, including a striker safety, a disconnect safety, and a trigger safety. These safety mechanisms help prevent unintentional discharges.
Firing Pin Return Spring
Sig Sauer’s P320 pistol, including the fire control unit (FCU), features an innovative modular design. This non-serialized core component houses the trigger, sear, slide rails, and other essential parts that make a gun function. The FCU is designed for easy customization and pairing with different slides, barrels, and grip modules. The kit includes the titanium nitride FCU, flat-faced trigger, and all the springs required for proper functioning.
The primary internal safety mechanism is not easily disengaged. Still, a lawyer representing officers in lawsuits against Sig Sauer asserted that it’s possible to disengage the safety by pulling the trigger just 0.075 inches, which could lead to an accidental discharge. This is one of the reasons that some police departments have stopped using the Sig P320 for duty.
As with any firearm, several factors can cause an unintended discharge, such as improper use and maintenance. Always be mindful of your surroundings and follow proper gun handling protocols. Also, be sure to clean and lubricate your weapon regularly.
Extended Firing Pin
Sig Sauer’s P320 pistol has been an outstanding success. However, some have pointed out that it may be susceptible to accidental discharge.
The Sig P320 FCU is the only part that carries a registered serial number and qualifies as a firearm in the eyes of the ATF. Other parts, like the barrel, slide, and grip module, are accessories.
Firing Pin Reversal Spring
The ring collar 11 on the firing pin has a recess trained to engage with a catch nose on the safety body. When pressed against this feature, the spring leg pushes the ring collar against the retaining ball in the recess, preventing the firing pin from moving forward to engage the primer.
Conventional “extra-power” springs have larger diameter wires and require more room inside the bolt body – friction can develop, lock time can slow, and ignition consistency inconsistencies may occur. The superior CS material of a new spring requires less space. It allows for smaller diameter wire, creating more reliable contact with the retaining ball and reducing friction for improved performance.
While the P320 doesn’t have an external safety, it does feature multiple internal safeties. A safety lock lever, disconnector, and secondary sear notch keep the striker from firing even if it slips off the primary sear surface. Those three safety features combined with an extensive inertia-reducing, skeletonized trigger help ensure that the firearm won’t fire accidentally.
Many shooters have complained that the P320’s lack of thumb safety is unsafe, but many disagree and have studied the design.
SIG Sauer has an extensive new program to make it easier for pistol fans to modify their P320s by selling FCUs as stand-alone units. These units will be finished in titanium nitride and include an enhanced, skeletonized flat-face trigger. Sig Sauer is partnering with carefully chosen aftermarket companies to make those modules and other parts available.