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SIG Sauer P320 Custom Works Program

SIG Sauer launches the P320 Custom Works fire control unit (FCU) so you can design your own.

SIG Sauer P320 Custom Works Program

SIG Sauer P320 FCU (Guns & Ammo photo)

A handgun is the most personal of firearms because it spends so much time in the presence of its owner. Whether it’s in a nightstand or inside a holster, pistols get more contact and attention than any other firearm. As a result of all that attention, pistols see heavy customization. The changes can just as easily be functional as cosmetic, and the only limitation is budget and imagination. The downside of customization is the inefficiency. Brand new parts on brand new guns often get tossed aside for the desired aftermarket components.

SIG Sauer has changed that wasteful process with its new P320 Custom Works program. This venture allows enthusiasts to purchase the P320’s Fire Control Unit (FCU), the serialized chassis within the P320 platform from a SIG Sauer dealer. With it, you can build out the rest as you see fit.


SIG Sauer’s idea behind its Custom Works program is to allow the user unrivaled control over the features of the pistol. What makes the program possible is SIG Sauer’s design of the P320 FCU. The FCU carries the firearm’s serial number. Legally, the FCU is the defined “firearm.” The barrel, slide, and grip module are all just accessories. Everything but the FCU can be purchased and shipped without ever having to set foot in a gun store. Do your shopping online, if you prefer.

While SIG Sauer always meant for the P320 pistol to be modular and user-configurable, making changes came at the expense of discarding unwanted factory parts or selling them to recover some of the gun’s original expense. (The MSRP for the most basic P320 Nitron is $549.) This is a minor consideration for many gun fans, but to a new shooter on a budget, the thought of chucking new parts is a tough consideration.

Enhanced grip modules and laser-­sculpted grip textures are being developed and offered for the P320 FCU by various companies including (top-­left then clockwise): Mirzon, ($119); Talon Grips Granulate-textured adhesive wrap (, $20); SIG Sauer TXG Tungsten (, $299); Wilson Combat WCP320 (, $65); L2D Combat (; and Gray Guns (; $115)

SIG Sauer’s Custom Works program presents us with new options. The first is the ability to purchase the FCU from a dealer and then source parts from third party vendors, some of which who have built a business around customizing the P320. If the customer isn’t familiar with manufacturers who have teamed with SIG on this project, the Custom Works program can help. Once the customer has the FCU in their possession, he then sources his barrel, slide assembly and grip module of choice. If a guy bought an FCU and decided to shop around for a grip, he could either buy one from (which start at $39) or from a third party. SIG Sauer currently offers several grip modules for the P320, including those with multiple lengths and dust covers that facilitate everything from concealed carry to competition and duty use. There is even a tungsten-infused heavy XSeries TXG grip module ($299), which is currently all the rage.

SilencerCo is one of the only P320 barrel makers offering a threaded barrel ($185). Besides its use for suppressing P320 pistols, it was used by PMM to affix their effective compensator (, Gen 1, $100). This combination does not fit X-­Carry slides. The comp on a P320 Compact slide is the same length as a P320 Full-­Size for use in full-­size holsters. Currently, PMM offers silde/barrel/comp packages for $355.

Historically, P320 owners who wanted something particular or more functional could take a Dremel tool and customize a grip module. Or, he could send a module off to someone else to work on it, or replace it with one from a third party business such as Wilson Combat’s WCP320 ($65). Customers either risked modifying their original purchase at the cost of some additional time or expense, or they paid to replace it with what they really wanted. This is why the program is big news. SIG Sauer’s new Custom Works allows the FCU owner to build exactly the gun he wants, using preferred aftermarket parts, the first time around.

SIG Sauer is also working on an online configurator called the “P320 Studio,” which will allow FCU customers to shop for barrels, slides, frames and other accessories available from SIG as well as from many of the partnered manufacturers. This means that, with a P320 FCU in hand, you can get on the P320 Studio and order a JTTC slide, barrel and compensator from Parker Mountain Machine ($355), and a grip frame from Mirzon ($119) to complete the pistol, for example. Parts ordered from SIG Sauer’s P320 Studio will come with a one time, 10 percent discount for all FCU’s registered in the configurator. Only SIG Sauer’s products will initially be available, but third party offerings will be added quickly.

Previously known for custom slides on several Glock models, L2D Combat expanded its offerings to include parts and assemblies for the P320. The complete upper assembly features an optic cut for Trijicon’s RMR and has everything needed to complete the upper half of an FCU build

The second major benefit of the FCU’s availability is the opportunity it presents aftermarket companies. Zev Technologies, for example, has customized polymer framed pistols for years. (They’ve even developed their own striker fired polymer framed handgun.) Zev is one of SIG’s partners for the Custom Works P320 program, which allows Zev the opportunity to purchase FCUs and what SIG Sauer calls “gunsmith slides,” in order to build their own Zev-branded custom guns. Like the savings a consumer sees from buying what they want, Zev has the ability to buy critical parts and finish the builds in their own signature configurations. Instead of being limited by starting with a factory finished slide, Zev buys partially finished slides and machines them to their desired specifications. Zev’s XCompact and XCarry Z320 Octane models retail for $1,299.

Grey Ghost Precision offers GGP320 slides in black and grey Diamond-Like Coating (DLC), or with an FDE Cerakote finish ( These slides are available for Full-size or Compact P320s with enhanced aesthetics and optic cuts that will accept the SIG Sauer Romeo1, Trijicon RMR or Leupold DeltaPoint Pro right out of the box.

Options Galore 

The P320 and X-Series has been commercially sold for some time, so there is already a good selection of aftermarket parts available. The P320 Custom Works program is the first, to my knowledge, that actively seeks out aftermarket partners and helps them promote and sell their products in support of the FCU. Where there are currently many options available, I suspect there will soon be even more. This kind of parent-company support for aftermarket, third party products is unprecedented.

Probably the most prominent aftermarket components for the P320 are grip modules. Choices are available from Wilson Combat, Icarus Precision, Mirzon and GrayGuns for a start.

This FCU build illustrates what’s possible. The trigger is GrayGun’s Adjustable Straight Trigger ($89), and the FCU ($350) is installed in SIG Sauer’s TXG grip module ($299). The Grey Ghost Precision Slide ($430) shrouds a SilencerCo threaded barrel ($185) fitted with a compensator by Parker Mountain Machine. Sights are from Trijicon, while a Streamlight TLR-1 ($125) hangs from the module’s full-size rail and a Taren Tactical +5 basepad ($42) increases magazine capacity to 22 rounds.

Icarus Precision offers aluminum frames that fit the P320 FCU ($370). These grip frames are made entirely of billet 7075 aluminum and have the top portion of the grip thinned considerably when compared to the standard P320 grip from SIG Sauer. This makes it easier for small hands to work the pistol’s controls. I found that these A-320 frames fit just about every hand well.

The Mirzon Enhanced Grip Module for the P320 has rubber panels inlaid in the grip ($119). Along with the rubber feel, Mirzon thinned the top of the grip and fattened up the bottom to allow easy access to controls while still filling the hand.

Coming soon! SIG Sauer is near launching the next-­generation Romeo2 red-­dot sight with larger window, protective shroud, easy-­access battery and recessed illumination buttons. The ruggedly durable sight is also convertible between operation as an open emitter or a closed emitter system.

GrayGuns is a long time player in the high end competition scene, and has a reputation for trigger components that significantly improve factory offerings. GrayGuns is offering laser etched grip modules for the P320 that look good and improve purchase on the grip ($115 to $165), but their triggers are my favorite products. The triggers GrayGuns sell look the same as the factory units, just with different shoe shapes, but that’s not all. GrayGuns’ triggers cost $89. They drop into the factory FCU and reduce pull weight by around 30 percent. More complicated trigger kits are also available to get pull weights even lighter while still retaining all the factory safety.

In addition to offering custom services, GrayGuns sells its Custom Fat Stainless Steel Guide Rod (, $25) that includes a 15-­pound recoil spring (14-­pound spring optional). Also known for its triggers, GrayGuns produces a drop-­in curved shoe that reduces trigger weight while preserving mechanical safety ($65), and an Adjustable Straight Trigger ($89).

Perhaps my favorite aftermarket grip module comes from Wilson Combat. Wilson Combat WCP320 grip modules feature Wilson’s distinctive Starburst pattern textured into the grip. While it may look like a modified SIG grip, the Wilson Combat offering is made by them. The WCP320 features significant changes that make it much more comfortable than the stock module, too, in my opinion. Selling for $65, it’s not expensive at all (which explains why they are often sold out on their website.) The grip has a slightly radiused frontstrap and heavily radiused backstrap that makes both narrower than the SIG Sauer P320 stock grip. When combined with the heavy scallops behind the trigger, the Wilson Combat grip frame feels great in the hand. I haven’t met anyone who disagrees.

Wilson Combat also places aggressive texturing on the front  and backstraps that makes the WCP320 module controllable in rapid fire. Wilson even integrated a weight system that allows the user to install tungsten or metal dowel rods to sit just behind the magazine inside the grip frame. (Adding weight to Wilson’s grip is similar those who have handled SIG Sauer’s X5 and Legion pistols.) This improves the balance and recoil characteristics of the P320. Lastly, Wilson’s integrated a magazine funnel into the module that speeds reloads without adding any bulk. What looks like a pretty simple grip module is thoughtful, subtle and performance enhancing.


SIG Sauer’s P320 Custom Works program doesn’t just include several options for grip modules. It covers the top half of the guns as well. Options for slides and barrels are available from Grey Ghost Precision, Parker Mountain Machine (PMM), Rival Arms and L2D Combat. PMM is a small shop just down the street from SIG Sauer who has sophisticated barrel/compensator/slide packages ($355) that integrate the compensator in such a manner that it looks like a factory product. The most impressive aspect is the performance that these packages offer. The assembly cuts muzzle flip to almost nothing! I was able to keep all shots in a relatively small group during rapid fire because the muzzle didn’t move. I never even lost sight of the red dot, which is another slide cutting service PMM offers.


Both Rival Arms and L2D Combat offer barrels, slides and parts kits that are a great way to complete any P320 FCU build. Rival Arms and L2D Combat make their own slides, but now SIG offers them the gunsmith slides. These slides have all the critical dimensions cut at SIG Sauer, but leave the slide’s exterior unfinished for Rival Arms and L2D Combat, should these companies decide to streamline their production. Rival and L2D can then integrate their slide cutting methodologies to hit SIG Sauer’s recommended slide-weight specs while still integrating their optic-mounting solutions, lighting cuts, texturing and aesthetic additions.


It’s a brave new world for handgun shooters everywhere. SIG Sauer’s effort to include and promote third-party manufacturers around the FCU program will ensure customers like us can get exactly what we want or need, even if it’s something that SIG Sauer doesn’t produce. Never has a handgunner had more great options available.


SIG Sauer P320 FCU Specs

Type: Striker ­fired, semiautomatic, chassis
Finish: Titanium Nitride (TiN)
MSRP: $350
Manufacturer: SIG Sauer, 603-­610-­3000,


SIG Sauer P320 FCU

Start building your P320 with SIG Sauer's Custom Works P320 Fire Control Unit.

SIG Sauer P320 FCU

Faxon Firearms Grey Ghost Precision


Parker Mountain Machine


True Precision Faxon Firearms


True Precision


Grey Ghost Precision Sig Sauer


Rival Arms


L2D Combat




Grayguns Grey Ghost Precision


Parker Mountain Machine


Parker Mountain Machine

SIG Sauer P320 FCU

Mirzon Faxon Firearms


Rival Arms


True Precision

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