SIG FCU Build Take 1 By: Clay Martin

Fire Control Unit from Sig Custom Works

The FCU’s have been flowing for some time now, I know. But I wanted my first build to be something magical, and that has taken time to source parts for. Finally, everything came together this week. I, for one, think it was worth the wait.

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SIG brand slide completion parts

What exactly is an FCU, anyway? It stands for Fire Control Unit and is like phase purple for SIG’s plan to completely take over the striker fired pistol market. (If you are keeping score at home, it’s working.) The SIG P320 started life as a modular pistol, with the trigger group being the only serialized part. Trigger group, chassis, FCU- it has worn many names. But basically, all the parts that make a P320 (or a P365) a “gun” are held together and retained in the frame by one pin. Take the slide off, drop that pin out, and the entire bit that makes it go bang comes free.

GoGun Gas pedal, a winning solution

Which originally was pretty cool, but maybe not earth-shattering cool. It meant you could buy one gun, and theoretically change its configuration to anything you wanted. Buy a full size, you can make it a sub compact. But when it started, the only real options were SIG brand caliber conversion kits and grip modules. So you could have any caliber and combination you wanted, as long as you still wanted a plain jane SIG P320.

Norsso Slides, and custom cerakote by MCM firearms

That changed big time with the FCU concept. The FCU is just the serialized bit, at a price significantly cheaper than a factory P320. And SIG took an unprecedented step in recruiting the aftermarket to make P320 parts. Many times, a manufacturer will jealously guard the secrets to how they make components. And they will be none too happy, sometimes even suing, anyone that starts making major end items for their gun. SIG was having none of that. They invited dozens of aftermarket names in pistol parts to NH, and told them about the project. I also have it on pretty good authority they actually handed over the prints for P320 slides, barrels, and grips modules to ensure the aftermarket parts were spec’d correctly.

Reptile C for this project, another Norsso on hand for another

Which is absolutely insane, and brilliant at the same time. SIG effectively not only encouraged you to make your dream pistol according to your own vision, but they recruited hundreds of outside machine shops to help. There is a massive difference between measuring a few off-the-shelf guns and trying to guess the tolerance standards, and being given those tolerance standards on a silver platter. With the FCU project, all of us win.

Ameriglo front sight

The FCU has some bonus features as well. A crisp 4.5 flat trigger, for starters, is slightly lighter than even the X series trigger groups. Custom FCU###### serial numbers are available for order. And an exclusive Titanium Nitride finish. SIG has available some excellent Pro series parts available as well, including a slide we absolutely loved.

Ameriglo rear sight

But for our first build, we wanted something different. We did use SIG Factory small parts, as they are the most available at the moment. And we actually used a SIG barrel, since everything else was on backorder. Welcome to 2021 logistics. But for the rest, we swung for the fences.

GoGun take down lever

First up was the all-important slide. We looked no further than Norsso, a company out of Las Vegas that specializes in aftermarket slides for EVERYTHING. Their catalog is so deep on the SIG P320 that we had a very difficult time deciding. We finally narrowed it down to the Reptile C for this project and the Vector for a near-future one. Norsso makes seriously cool stuff, and you leave their website wanting one of everything. True to reputation, the Norsso slide was dimensionally perfect and went together as it rolled off the assembly line in New Hampshire.

Gas Pedal installed

Next, we picked up an X-carry sized grip module from SIG. That is my favorite size, and when we started the parts collection, true aftermarket was impossible to find. But to spice it up a bit, we turned to our buddies over at MCM Firearms for a custom cerakote job. We picked Multicam because we all believe I won’t drop this gun in the woods and lose it all time. The Multicam job came out perfect and adds a very distinct look to this already sharp pistol. The Norsso slide looks even more magnificent with a coat of custom gun paint.

Tested with Hornady XTP

For sights, we were hard-pressed. The SIG factory night sights are great, easily my 3rd or 4th favorite option of all-night sights. But we did want to step out a bit, so Ameriglo was the weapon of choice. Ameriglo makes fantastic night sights and a wide variety of them. We chose the $80 protector series, with a tritium front and black rear. The tritium front is ringed by high visibility paint, making this Ameriglo a great choice day or night.

Last but certainly not least was a Go Gun Gaspedal takedown lever. This is a simple-looking device that is worth its weight in gold. Or 9mm, roughly the same price right now. The Gas Pedal is so cool that SIG sells it in their own online store, though you can get it from Go Gun direct as well. The shape of the Gas Pedal for the P320 acts as a shelf for your nondominant thumb, and lets you get some very real leverage against the forces of recoil. This is basically a tactical version of their famous competition OPP Grip, tactical in this case meaning nonobtrusive and you don’t need a special holster. (It fits my Safariland and Red Ballon with no modifications.) The Gas pedal is a stunning addition to any gun, and the SIG geometry lets you install it in place of the take-down pin. How good is it exactly? I can’t say it any better than they do.

Not convinced? Opposable Grip took Clean Sweep in 2015 National Championship, winning High overall, Men’s, Ladies, Senior and Junior. Winning don’t lie. Still not Convinced? How about REPEAT championships 2015, 2016 by Chris Tilley with Gas Pedal® brand. How about the fact that in the last 6 years of National Championships, the lions share of top five finishers all used opposable grip and 7 of 8 last champions used the opposable grip.”

STILL NOT CONVINCED? OPP Grip won every year from 2015 to 2020 US Nationals AND 2017 World Championship. “ ( courtesy GOGUNUSA.COM)

The FCU is an absolute winner, and a joy to build. Build is a strong word. Assemble the gun of your dreams. With an FCU, the sky is the limit, and options grow every day. Grab one and start looking up aftermarket parts, this is a purchase you are never going to regret.