The Sig Sauer M18 Comes to California By: Brian Jensen

Sig Sauer M18 P320 with magazines on a California flag
After close to 10 years, Californians now have a new option for semi-auto firearms.  The Sig Sauer M18 P320 is now on the California Roster…and is flying off shelves.

Table of contents

  • The Challenge of California Gun Laws…
  • Sig Sauer Steps In
  • Features on The M18
  • Making California Happy…
  • Common Sense
  • Shooting The California M18
  • Red Dots…Sig’s Romeo X
  • Final Thoughts On The M18

California is seen by many as a great place to visit, vacation, and see the sights with its beaches, mountains, and parks.  But for those in the Gun Rights community, it is seen as the worst-case scenario.  It’s no secret we have some of the toughest gun control laws in the nation. 

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One of the most onerous issues is a roster of “safe handguns” that are allowed to be sold to the public in the state.  The requirements on this roster have prevented any new semi-automatic pistols from being added to the roster since 2013, and many on the roster are 20+ years old technology.  Think about that for a minute….  We are legally forced to live with outdated designs that are inferior to newer, safer guns.

Sig Sauer handgun modified to be allowed in California with light installed
The Sig Sauer P320 M18 comes in a slightly two-tone FDE with black controls.

You can get guns that are not on the roster used by law enforcement (who are exempt) and those who move to California with these “off-roster” guns can bring them in and potentially sell them.  However, this market makes for some outrageous prices, such as $1500+ for a P365 or P320.

Available on GunsAmerica Now

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    Safariland SL 7360RD SLS/ALS L3 P320 BLK RH


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    Sig Sauer P320 Flat Trigger 8900095


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    Grey Ghost Precision GGP SLIDE COMPLETION KIT P320


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    Grey Ghost Precision GGP SLIDE FOR SIG P320 FLLSZ V1 BLK


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    True Precision TRUE PREC P320 X-CMP 9MM BLK TB


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    ProMag PRO MAG SIG P320 9MM 15RD SCMP


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    Elite Tactical Systems Group ETS MAG FOR SIG P320 9MM 30RD CRB SM


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    Grey Ghost Precision GREY GHOST SIG P320 FULL SIZE SLIDE V1 GREY


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    Sig Sauer P250/P320 Replacement Magazine MAGMODF4314


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    Sig Sauer P250/P320 9mm 17rd Magazine MAGMODF917


Recent court cases have now allowed new gun models with state-required safety features to be added to the roster.  (A requirement for micro-stamping is no longer valid…)  I cannot overstate how huge a development for the citizens of California this is. 

In July 2023 the first truly new centerfire semi-auto pistol to be introduced was announced…the Sig Sauer P320 – M18.  This is the version of the striker-fired P320 family adopted by several branches of the U.S. Military.  I saw the news that now we can have more modern choices.  I soon put my money down on deposit for one, and was told to expect its arrival in August. In a couple of months, my M18 was here. 

The M18 is the military pistol adopted by the Marines, Air Force, and Navy.  It is a polymer framed, striker fired pistol set on the modular Sig Sauer P320 system.  The standard capacity is a 17-round magazine and two 21-round magazines.  The M18 is the more compact version of the M17, with the M18’s 3.9 inch barrel compared to the M17 4.7 inch barrel.  It has night sights, and an integral optics mounting system using the Sig Romeo / Leupold Delta Point Pro footprint.

Closeup on the serrated slide of the M18 P320
Proudly marked on the slide, Sig Sauer P320 M18

Looking over the California M18 at first glance it looks identical to any other version.  The desert tan slide and polymer frame offer a two-tone look, each being slightly different in color.  The black accents of the controls, trigger, barrel, and optics plate provide great accents.  As with other M18 variants the gun comes with night sights.  The rear sight is attached to the red dot sight plate with two tritium vials against black steel and a front sight is dovetailed in the front of the slide that has a nice white dot with Tritium that jumps out at your eyes.

Pile of Sig Sauer handguns resting on checkered blanket with magazines and accessories
With the introduction of the P320 M18, shooters can now customize their guns to them, pick your grip frame, pick your slide, or mix and match.  The P320 system is one of the most versatile in the world.

The biggest questions were how would the M18 accomplish two of California’s three main requirements?  The Golden State requires guns to have a manual safety, a magazine disconnect safety, and a chamber-loaded indicator as specified by the California Penal Code. 

The magazine disconnect is integral to the FCU, so outwardly you’ll never see a difference.  The purpose of the safety is to disable the firing mechanism when there is no magazine in the gun.  (I know there are differing opinions on this feature…)  The mag disconnect works like a lever that gets pushed up and out of the way once a mag is inserted.

magazine disconnect system on the Sig Sauer M18 P320
The magazine disconnect system is a lever that is attached to the FCU that pushes up and out of the way when a magazine is seated, allowing the gun to fire. 

However, the Chamber Loaded Indicator (or “CLI” as it’s referred to) is usually a god-awful metal flag that pops up when there is a round in the chamber – in some guns, it can even be seen in your sight picture.  These CLI’s can break, potentially take the gun out of commission and this is especially true where they are placed, as almost always, on the top of the slide where they strike the holster on re-holstering.

Loaded Chamber Indicator on Sig Sauer handgun
The Loaded Chamber Indicator is the standard M17 / M18 system but with the words “LOADED WHEN UP” written on the optic plate. 

Sig used a not-so-common attribute – common sense.  They kept the loaded chamber indicator like all other M18’s, and added wording on the optic plate that says “LOADED WHEN UP” with an arrow pointing to the loaded chamber indicator.  A simple, and legal solution.  Once I add an optic, the plate will be off and you won’t tell the difference between this M18 and any M18 outside of California.

The California FCU works in any other P320 grip module that has the cutouts for thumb safety.  I chose an FDE Sig X-Carry grip to customize the pistol for me.  (Wilson Combat also makes ones that should work.)  I found a black M17 slide that set nicely on the grip module / FCU.  There is no reason I can see that any other upper wouldn’t work as well.  Pick your upper, pick your grip module, and enjoy. 

I work as an instructor for a local Police Academy.  One of our bigger agencies issues the P320 as their duty pistol, so this fell right in as a teaching aid.  On my first outing, I took the M18 out and put 200 rounds downrange with zero issues.  I was hitting steel easily at 40 yards.  Drills on dual steel targets at 10 yards became easy with the Sig, putting shots where they needed to go repeatedly.  The sights were excellent for picking up and making shots at a distance. Recoil was milder than expected to put it bluntly.    

Shooting the M18 P320
While shooting the P320 M18, recoil was mild, if not downright pleasant…

The gun only comes with 10-round magazines since this is California.  That being said, magazines fell freely from the mag well despite the magazine disconnect lever.   Reloads were just as quick with magazines slipping quickly, and securely into place. 

After my initial 200-round outing, I wiped down the gun, and removed all the gunk (I know…that’s a technical term…).  Then, I completely forgot to re-lube the gun.  I then shot an additional 350 rounds at the range where mags got dumped in the dirt and I treated the gun fairly rough.  I did a lot of rapid-fire, and accuracy drills – there was only one malfunction that was due to a bad primer.  Period…full stop.  To put it simply – this gun just runs. 

Sig Sauer M18 P320 on pile of shiny ammo
The author fired over 1000 rounds through this gun, without a single non-ammunition failure. 

I’m also getting into the red-dot system, and the M18 was a host for the new Sig Romeo X Pro.  It’s an open emitter optic that’s built…well like a tank.  There is a video out there of a prominent YouTuber using a Sig slide with the Romeo X as a hammer…and he isn’t being gentle.  That thing kept zero without losing a beat. 

The Romeo X uses a Sig Romeo / Delta Point Pro footprint.  So, it direct mounted to the M18.  Its low deck height also allows you to use the factory sights, incorporating a rear sight assembly into the back of the optic.  The RDS has a side loading 1632 battery so you don’t have to remove the sight and re-zero for a battery change, and uses multiple reticles (a dot, a circle dot, or just the circle).  I gave it a brutal range session where I used a wood beam barricade for single handed manipulations.  No loss of zero, and not much scarring on the sight…like none.    

M18 P320 with four magazines, used ammo casings, and Streamlight flashlight
The only part of the pistol that showed any wear at the end of 1000 rounds was the magazine finish…

So, after putting over 1000 rounds downrange in the last few weeks, the gun has run flawlessly.  The only malfunctions were ammo related (I had two rounds that were dead primers…).  This pistol will allow you to configure the gun to you with grip modules, slides, optics, etc.  This offers the first optics ready, modern handgun we have seen in almost 10 years here.  I am very impressed, and as I continue using it to teach, I really enjoy it.  It is bulkier than other mid-size guns, so keep this in mind as you look at this for CCW.

READ MORE: Small Caliber, Big Upsides: Force 22 TB Rimfire Pistol  

I commend Sig for remembering that California consistently ranks as the number 3 or 4 market in the country and bringing us the M18.  This was a great first step in this new era for us here in Cali.  We hope to see other offerings, such as a P365.  Moreover, this should be a challenge to other manufacturers, it’s time to step up to bring their offerings to the California Roster. 

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