Difference Between Sig P320 M17 vs Sig P320 M18

The perfect time of the year to get your SIG is Christmas, right? If you are eyeing the twin brothers M17 and M18 from the SIG P320, this article is for you.

There are many subtle differences between the both. Choosing one depends on the type of use you are going to get. But the M18 is better by the margins of minute accuracy, ease of shooting and other differences between the two.

So stay tuned till the end of this article and find out!

Sig P320 M17 vs Sig P320 M18: Quick Comparison Table

SpecsSig P320 M17Sig P320 M18
Cartridge9mm Luger9mm Luger
TypeStriker-fired semiautomaticSelf-cocking striker-fired pistol
GripCoyote-tan grip moduleCarry polymer medium
Length8 inches7.2 inches
Height5.5 inches5.5 inches
Width1.3 inches1.6 inches
SafetyNo manual safety; MS version has oneAmbidextrous manual safety
SightsSIGLITE front; removable Night Sight rear plateSIGLITE front / Night sight rear plate
Capacity17+1 rounds17 or 21 rounds
Barrel Length4.7 inches3.9 inches
Weight13.6 oz28.1 oz
Barrel MaterialCarbon steelCarbon steel
Trigger Pull8 lbs.5.5-6.8 lbs.
Sig P320 M17 vs Sig P320 M18
Sig P320 M17 vs Sig P320 M18

What’s The Difference Between Sig P320 M17 and Sig P320 M18 Based on Features?

Between these two guns, Which one to get depends on the ease of use. Because there’s very little difference between them. Let’scheck them out.

Feature 1: Size

The M17 is a full size and has an approximate eight-inch overall length. Its height is 5-1/2 inches and its width is 1.3 inches. It also weighs 29.6 ounces.

The M18 on the other hand is 7.2 inches long and 1.6 inches wide, with the same height as the M17. It weighs 28.1 ounces.

Now both the pistols have striker-fire barrels measuring 3.9 inches and 4.7 inches, respectively. However, the M17 is a lot wider so for conceal or carry, the M18 has the advantage of being light.

As both magazines are interchangeable, I would say that you can be sure to buy the M18 for a carry gun and the M17 to be a defense gun.

Feature 2: Recoil Spring Assembly

The M17 RSA can be swapped for a solid Full-length guide rod, enabling the use of 1911 springs to tune for different loads. The M17’s longer, single spring does not work as hard as the M18’s

Although both will last much longer, the M18 has a 5,000 round recommended replacement interval and the M17 has a 10,000 round recommendation.

However, the P320-M17’s recoil spring seems absurdly frail. You can feel the slide going ‘ka-chunk’ and stuttering at the end of its backward travel or gradually easing the slide forward while firing the pistol.

Feature 3: Accuracy

Both are very accurate guns. In the case of the M17, the gun would produce 2 inches at 25 meters. This can be found with CCI Blazer Brass, 124-grain FMJ.

The M18 at a range of 25 yards also produces somewhat similar results.

All these tests must be done with at least 1000 rounds. And the data collected in this article was of 10,000 rounds. So I would say both are very accurate guns.

Feature 4: Ammo

Anything hotter than NATO-spec ammunition should not be used with the M17 because that is what it was built to handle. It would be best to use Sig 9MM, 124GR, ELITE V-CROWN, Crosman LM77 Premier .177-Caliber Match Grade Pellets etc. Look into Federal HST as well.

All of the following ammunition is suitable for the M18: 124-grain FMJ and carry 124-grain JHP, Winchester 124gr NATO, 115gr range ammo by Winchester, Federal or Blazer Brass (brass cased), and Federal 124gr HST standard pressure. The 124gr NATO ammunition that was intended for the pistol is 10%–15% hotter than typical 124gr ammunition.

The pistols use more or less the same kind of ammo. So there is no budget-friendly advantage.

Feature 5: Sights

The sights on the M17 can occasionally be problematic. According to information floating around on the internet, the GI version is distinct from the civilian model and has screws attaching it. The bullets would hit the target at 7 yards about 6 to 8 inches below the point of aim.

The DPP and Romeo 1 Pro are the native sights that simply mount up because the M18 has a delta pro footprint. Any other thing that fits that footprint also functions. Romeo 1 Pro is a bit of a hit and a miss.

It seems though, the sights of the M18 are likely to perform better. A Vortex Venom optic or a 507c are some popular optics for the M18.

Sig P320 M17 or Sig P320 M18 Which One to Choose?

The M17 P320 is the standard issue across the military. However, they have started using the M18. It is more compact and was integrated for specialty missions, according to the military.

I don’t favor either over the other. If I had to choose, I would choose the M17, and I might then suggest the SIG M18 conversion kit. You would have both that way, as the Army had intended.

Having said that, I guess I do favor the M17’s balance. Better ballistics are made possible by the M17’s slightly longer barrel (which it does have).

It may be 50 FPS faster than the M18 for an average 9mm round due to the 8-inch difference. It may also have a slightly less muzzle blast. Because of the M17’s longer barrel and slide, it weighs more and has slightly less recoil than the M18.

The M17’s slightly longer barrel provides a slightly longer sight radius and a little bit more usable accuracy than the M18. These variations favor the M17 by small but noticeable margins.

It depends on which one is simpler to use and feels more comfortable for your hands.

How are the Civilian and Military M17 and M18 Different?

The color of the controls had been the difference between civilians and soldiers. All of them now share the same color.

Barrels used by the military differ in these guns from the ones used by civilians. The military versions have loaded chamber indicators (LCI’s).

Additionally, the rear sight is held in place by one bolt on the military slide. The commoner employs two.


For people who do not feel comfortable with the light “first shot” trigger pull on the striker-fired models, they might as well get one of the M17 or M18s.

However, looking at this article it is safe to say that M18 may become your ‘it’ gun. Good luck for your purchase!

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