SIG M17 Review - A P320 Worth Buying? [2023]

Disclaimer: This review is not sponsored, and all of the products featured were purchased by the author.

SIG M17 Featured Image

Back during the COVID craze of 2021, I decided to start a new gun project. I was fascinated by the B&T USW, and the version that took SIG P320 parts caught my eye. With that being a PDW/pseudo-SMG, I wanted a manual safety. That lead me to the topic for today, the SIG M17. While I made the USW project, I ended up spending a lot more time with the M17 in a traditional form, rather than in the USW chassis. What is the M17, and what makes it worth buying? Also, how's the M18?

What Is the SIG M17?

To discuss the M17 is to discuss the XM17 competition. The XM17 Modular Handgun System (MHS) was a competition that was done in the mid-2010s. The MHS's goal was to replace the Beretta M9 handgun with a new, more modular handgun. FN, Glock, SIG, and a few other companies submitted guns, which has lead to an onslaught of commonly owned pistols now. The FN509, Glock 19X, Beretta APX, and SIG M17/18 came out of the trials. SIG won, with the M17 and M18 becoming the new US Military handguns. You can read the full details in the Wiki article linked above.

The M17 is a double stack, striker fired 9mm handgun. Barrel length is fixed at 4.7", and magazine capacity is 17 rounds with flush mags, and more with extended magazines. The gun ships with iron sights, two 17 round mags, and one 21rd magazine. A calling card of the M17 and 320 is the Fire Control Unit (FCU). MSRP is $768.00, however, street price runs about $550-$680. I paid $599 for the M17, and $580 for the M18.

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SIG has been using a serialized FCU assembly since the P250 series of handguns. The FCU is "the guts" of the lower half of the gun, containing the trigger components, controls, and slide rails. With the FCU, that is the "gun", as in, the serialized, regulated part. Unlike more standard handguns, the frame itself is not the serialized part, and can be swapped easily. The M17/M18 FCUs are marked as such, and have cutouts for manual safeties.

The M17 is not a radically different gun, however, it is different than a standard P320.

What Differentiates the M17 From the P320?

So, what is the M17? Essentially, it's a manual safety SIG P320, with a standardized optic cut. The P320 likely needs no introduction, but to make a long story short, it's been SIG's polymer framed striker handgun for the last decade. While not a massive departure, the commercial M17 takes the military offering, and slightly changes the finish of the gun, and some select parts.

SIG M17 Safety Control Lever
The black-finished controls of the commercial M17.

The M17 has a manual safety. While not the first P320 with one, this model only comes with manual safeties. They are ambidextrous safeties, as are the slide releases. The commercial guns come with black finish controls, while the military/commemorative models are tan. Standard P320s are generally without manual safeties, simply relying on internal safeties and not pulling the trigger. A nice element of the M17 is that during "Dropgate" of 2017, the manual safety 320s were not having the drop safe issues, due to how the safety interacts with the trigger assembly, even when the safety is off.

SIG M17 R2 Optic Cut
Underside of the R2 optic cut.

The optic cut of the M17 is the "R2". This cut will direct mount anything that uses the Leupold DPP footprint, however, plates can be fitted to mount different optics. This optic cut goes directly through the slide, with screw holes visible in the underside of the slide. For the duration of my testing with both my M17 & M18, I used APEX ACRO plates.

So, we've got two features that separate the M17 from the normal P320. What's the difference between the M17 and M18?

The SIG M17 vs the SIG M18

It's just slide, barrel, and recoil assembly length. Yep, that's it. The frames and FCUs for both pistols are the same, taking the same magazines and parts. Both have the same optic cuts too. The difference is merely that the M17's slide pokes past the accessory rail on the frame, and the M18's slide ends at the end of the frame.

M18 Right Side
The slightly shorter SIG M18, with a Wilson Combat frame.

Barrel length on the M17 is the aforementioned 4.7", while the M18 is 3.9". SIG markets the M18 as the "carry gun", and the M17 as the "duty" option. I've put a lot more rounds through the M17 during my testing, however, the M18 was still shot a ton. With both guns being very similar, this was a boon for shooting, and familiarity.

A minor thing to note is the slide finish. The M17 I shot and used was an older production gun (2019), and the slide was black finished. The M18 was a 2021 production gun, with a peanut butter FDE color. As of time of writing (Winter 2023), all M17/M18s come with FDE frames and slides.

What's the field strip and takedown like on the M17?

Field Stripping & Detail Stripping

The M17 is a simple gun to field strip.

  1. Remove magazine, and verify that gun is empty.
  2. Lock open the slide, using the slide release.
  3. Rotate the takedown lever.
  4. Slowly release the slide, allowing the slide to come off of the frame.
  5. Once the slide is fully off of the frame, remove the recoil assembly and barrel.
  6. To reassemble, reinsert the barrel and attach the recoil assembly to the slide cap, and barrel notch.
  7. Verify that the takedown lever is still in "takedown" position, and install the slide back on the frame, being sure to engage the slide release up when the slide is fully rearward.
  8. Rotate the takedown lever back down to the "standard" position.
  9. Function test firearm.
SIG M17 Field Stripped
A field stripped M17.

Detail stripping the M17 is a bit more complicated. While I won't take apart the FCU, I do have a video showing the field strip, and FCU removal from the frame. It isn't too hard to do this, however, you shouldn't need to take your FCU out of the frame unless you are changing parts.

One of the things I've found is that while the FCU comes out of the gun, it isn't super easy to work on. One of the nice things about traditional handgun frames is that you can pull certain parts out, and leave other ones inside. When I installed my APEX triggers, that was about an hour of work to install it. On a similar traditional gun, (Glock, M&P), it would be a ten-fifteen minute job.

Speaking of modifications, what did I do to my M17?

Modifying the M17

In the nature of full disclosure, I did not shoot my M17 or M18 stock for very long. Over the last two years, I've written a host of reviews for upgrades to the guns, and most of the upgrades remained in the guns.

SIG M17 Left Profile
The upgraded M17.

For both pistols, I upgraded the frames. I wrote a review for the Wilson Combat WCP320 grip back in 2021, and I'm still using those. They offer better texturing and posit the finger better onto the trigger. With the WCP320, you can also toss tungsten weights into the frame which I chose to do midway through 2022.

SIG M17 Recoil Assembly
The OEM recoil assembly on the left, and the Wilson guide rod and spring on the right.

Speaking of Wilson parts, I also dropped in their 1911 recoil spring conversion for the M17. This replaces the standard guide rod with a steel one, and allows the gun to use 1911 recoil springs. This, in conjunction with the tungsten weights, made the M17 a smoother shooting, softer pistol to fire.

As mentioned before, the APEX flat face trigger kits were installed in both the M17 and M18. These dropped the pull weight about half a pound (pulls at a consistent 5.8lbs), but more importantly, moved the trigger to be a little more rearward in the trigger guard. The pull length became shorter and more consistent, and the overtravel stop in the APEX kit made a big difference too.

For sights, I used Aimpoint ACRO P-1 & P-2s on my guns. The APEX BUIS plates worked well, and allowed for proper co-witness of the irons through the optics.

The aftermarket for the 320 is excellent, no need to mince words. How did my SIGs perform while shooting?

The M17 At the Range - Reliability & Ergonomics

As always, we need to discuss reliability. I fired just shy of 9,000 rounds through my M17 during my time testing it, and about 2,500 in the M18. A wide range of ammo was fired through the gun, from weak 115gr ball to 147 hollow point ammo. Most of the diet was 124gr NATO spec ammo during 2021, and 124gr standard pressure ball in 2022. Reliability was perfect during the entire testing run, aside from while I was testing the garbage ETS mags. I keep my guns fairly lubed, but not necessarily clean. The M17 just feeds and feeds and feeds.

The M17 survived the bean-pocylpse.

When using good magazines in the M17 (OEM or ACT Mags), reliability and magazine insertion and extraction were great. With metal magazines and a polymer frame, I've found that mags will shoot out of the gun when you hit the magazine release. A great feature, as every reload felt smooth on the M17.

The controls on the M17 are quite nice. On both my M17/18, the safeties were very positive, and had a tactile click. The slide releases also worked great, with them locking open on every empty mag. A 1911 style support hand method is needed to hit the release when reloading, but that's fine by me. On both the unmodified Glocks and VP9s I've shot over the years, neither would reliability lock open on empty. I was extremely pleasantly surprised to have the opposite experience with the M17.

While not tied to shooting, both the M17 and M18 carry well. I used a PHLster Floodlight for CC during my testing, and Safariland 6360s for overt use. With the Wilson frames, I found no hotspots while carrying AIWB.

The M17 At the Range - Shooting Characteristics

I never benchrested the M17, as I exclusively offhand shoot. This pistol will keep everything in the black of a B-8 at 25 easily, if you have the skill to do so. Practical accuracy is excellent, and many drills were shot with this pistol over the years.

Recoil impulse on the M17 is fairly soft, but is more upwards than I normally like. Even with my Wilson mods, the gun still had more slide movement than a Glock or M&P. It's not harsh recoil but it does upset the sights a fair bit. The M18 has slightly more recoil than the M17, but not a ton.

The biggest gripe I have with the M17 is the trigger. Before and after my upgrading, the trigger pull still feels weird. The trigger has a very "squeeze" feel to it, like pushing on an older keyboard. The trigger is by no means bad, but it isn't as good as I'd like it to be. I did feel as though I had shots pulled due to the oddity that is the M17 trigger feel.

Dryfire is also strange with the M17/M18, as the way that the FCU interfaces with the slide leads to some wiggle. The slide will move up and down a hair when the trigger is depressed. This only happens with an empty magazine in the gun, so dummy rounds in the mag fix the issue. However, a chambered gun still has this issue, so it will effect live fire. I do not like that.

I've got a playlist of all of my M17/M18 drills here.

Pros Of the M17 & M18


  • Excellent ergonomics
  • Good build quality
  • (Generally) good shooting characteristics
  • Excellent aftermarket

The M17 is basically a SIG doublestack 1911, in regards to the ergonomics and controls. I like the placement of the controls, and how they all work. While I quickly ditched the OEM frame, that frame was quite comfortable.

M18 ACT Mag
Even the OEM frame felt pretty great when shooting.

Build quality is generally good. While SIG has certainly had a mess of lemons leave their factory, both of my guns were well made, having no defects or issues. Assembly and disassembly are simple, and with the good build quality, it is a fast process.

Accuracy and reliability of the M17 is excellent. I shot really well with mine, and find them to be soft shooting, and easy to shoot.

Lastly, the aftermarket support is great on the M17. A mess of companies are providing parts, frames, and optic plates for these guns. With them being the Army's current handgun, you'll have plenty of support moving forward.

Cons Of the M17 & M18


  • FCU is difficult to work on
  • OEM mags are expensive
  • Recoil impulse will be difficult for shooters to overcome
  • Trigger pull leaves a lot to be loved

The FCU is a great design in regards to aftermarket modifications, and US gun laws, but it sucks to work on. It is a tiny hunk of metal, and swapping parts can sometimes feel like an exercise in futility.

The OEM mags are very pricey, running over $40 USD at the time of writing. While aftermarket options exist, high-dollar OEM mags still suck to have to pay for.

While not bad, the recoil impulse of the SIG is very much going to be a limiting factor for shooting fast. The gun has a fairly heavy, tall slide. With this, you have more upwards recoil as the gun cycles. I found it to be a factor that prevented me from shooting the gun as fast as something like a Glock, which has more inline recoil.

M17 Strange Trigger Feel
A strange trigger feel, to say the least.

The trigger pull is very meh. It isn't bad, but it isn't great either. When compared to a stock Glock, VP9, PPQ, PDP, or M&P, my two SIGs both feel worse than those.

Do I recommend the M17?

The Verdict

The P320 was a platform that I was very hesitant to get into. SIG treats the public market like Guinea pigs, and I don't like that. When I wanted to get a P320, I wanted to get the one that I felt was the most inherently safe model. I do recommend the P320, but only the M17 or M18.

I will not carry a striker fired handgun unless it has a manual safety, or some form of trigger safety (dingus, hinge). While I practice safe gun handling, holstering, and reholstering, the lack of either safety on the standard P320 has made me dislike it. However, the M17 and M18 fix that issue, and do it in a manner that doesn't hurt the performance of the gun.

M18 Left Side
The M18 and its bigger bro are excellent pistols.

I really enjoy the M17 and M18. Both are reliable, accurate, and easy to modify guns. You'll find parts and holster for them easily, and you'll have support for the next few decades. However, the shooting characteristics were an issue for me. When put on the clock against similar handguns, I shot the M17 a little worse than the VP9 and Glock. Despite the "me" issues, I can easily recommend the M17 or M18. Admittedly, they are the only 320 variants that I think are worth buying.

In Closing

Well, here's where I tell you that I've already sold my M18, and will be selling my M17 soon. While the guns generally performed well in my time spent with them, I found that the triggers and recoil impulse were unfavorable. I've been working on shooting more accurately and faster, and I'm doing that much better with other handguns.

While this might sound contrary to the last subheading, I still really like the M17. While I will soon be without one, it's not due to disliking the gun, but rather, wanting to hone in even more on the skill I've got on a different platform.

SIG M17 & Glock 17 Gen 5
Out with the old, in with the older?
About Paul Whaley 197 Articles
Paul Whaley is a guy with an interest in practical and defensive pistol shooting techniques with an eye for quality gear. He has received training from Holistic Solutions Group, John Johnston of Citizens Defense Research, Darryl Bolke, Cecil Birch, and Chuck Haggard. When not trying to become a better shooter, he can be found enjoying a Resident Evil game or listening to Warren Zevon.

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