SIG Sauer P320 Nitron, 9mm: modularity changes everything!

SIG's P320 is taking pistols to a new level of modularity

SIG Sauer P320 pistol review

The SIG Sauer P320 takes handguns to a new level of modularity. It has become hot property among handgun enthusiasts, since the US armed forces adopted the military version, the M17, in 2017. 

Why all the fuss about just “another” polymer, striker-fired 9mm pistol (yawn)? For the most part, these pistols are almost indistinguishable from each other, but in the P320’s case it’s all about individuality. It is built to be customised.

I obtained a basic SIG 320 Nitron from Cleaver Firearms to use for instructing new shooters, following requests from many people to try it.

First impressions: 

  • It’s just another polymer 9mm: looks OK, great fit and finish but a bit blocky.
  • It’s highly reliable: zero malfunctions in over 900 rounds so far with many different types of ammo.
  • Reasonable practical accuracy on the range for IPSC or action-type shooting competitions or for security work.
  • Reasonable trigger for a striker pistol, perfectly fine for intended purpose.
  • Generally a very practical choice for users, but not anything earth shattering.

But wait, there’s more. Much more…

SIG Sauer P320 review
P320’s constituent parts with Fire Control Group still in the frame

When I received the pistol, I was running late for a safety class and so did not do my usual full strip and clean of a new firearm, but was forced to simply check the barrel was clear and the slide worked. Then it was loaded and used with over 100 rounds by five students, all of whom were happy with the gun. Two of them absolutely loved it.

If you want to watch a video review of the same firearm, our friend Ozzie did a review of the standard, unchanged SIG 320.

It was then placed in the safe dirty and left for a week until I had time to take a close look. When I disassembled and cleaned it, when the penny dropped and I realised the SIG 320 has a special place in the evolution of the modern pistol.

SIG Sauer P320 review
Fire Control Group at the heart of the P320 is the secret to its modularity

Of course, I had already heard the marketing hype from SIG about the “Ultimate Modularity” of the 320 but to be honest I had not paid it much attention as gun companies tend to oversell minor advances all the time.

But as I took the gun apart I realised this is a very special beast. It is truly amazing in how you can customise this pistol to suit your own needs and make it your personal treasure. 

Forget anything you every thought about the frame being the firearm for legal purposes. The 320 turns that it on its head. The serial numbered part (which is legally the registered gun) is actually an easily removed internal Fire Control Group, containing the trigger assembly and action. 

SIG Sauer P320 review
Aftermarket grip modules can instantly change the P320’s character

This part simply pops out of the gun as a unit with two pins for cleaning or to totally change the gun’s personality and performance by changing the frame to an aftermarket version. I cannot emphasise how much this can totally change the feel and shootability of this pistol.

When I had picked up the firearm, I had been supplied with a ‘spare’ frame made by top-end company Wilson Combat. I was intrigued about how a polymer grip frame could make much difference.

It took about five minutes to fit the SIG 320 fire control unit into the Wilson Combat grip frame. It was quite tight and stiff but then popped into place like it belonged there.

Suddenly the gun had a whole different look about it. It was no longer another boring 9, it actually seemed to have personality. In my hands, it had truly been transformed, feeling fantastic, and nothing like the factory grip. I can’t adequately explain the amount of change. It was like a whole different gun. 

This isn’t to say the original grip may not feel fine in your hands. The point is that this system provides as many alternatives as the market can supply, if you want them.

Taking the now SIG/Wilson 320 back to the range and putting it through its paces I was excited and most pleased. I was noticeably faster and more accurate on different action shooting drills and I noticed that where with the factory grips I had been constantly shooting several inches low, this now vanished, a factor of the changed grip angle. Even the trigger felt smoother and a touch lighter, although it was fine to begin.

The 320 went from merely decent to exceptional for me, still 100% reliable but looking, feeling and shooting better. It was a different gun and my new best friend at the range.

Two of the people who had shot it in its original frame were at the range. Both agreed it looked far better, but only one found it also shot better (faster and more accurately in drills) while the other liked the original grip frame feel more.

SIG Sauer P320 review
It may not look it, but the SIG Sauer P320 is not a typical striker-fired pistol

With the quickly growing popularity of the 320 series in the USA, combined with SIG allowing and encouraging aftermarket suppliers to develop and sell frames, triggers, slides and almost anything you can think of, this 320 format is becoming very attractive for those who love to personalise and customise their firearms to suit themselves.

Almost weekly it seems there are more accessories and add-ons available for this truly innovative pistol platform. In years to come people will look back and see how the 320 changed the world of pistol modularity in a way never achieved before.

SIG Sauer hasn’t missed its own boat, either. There are now over a dozen quite different 320 models on the market to suit your taste and wallet size. Whether you are a high-end competitor, club plinker or work in security there is a model for you. The amount of versatility and modularity will amaze you when you check out the full range.

Accuracy off the bench

SIG Sauer P320 review
SIG Sauer’s accuracy at 25 yards is probably better than our shooter’s!

Once I realised what an interesting gun this is, I sat down at the bench and using a rest was able to obtain groups around 50mm (2 inch) at 25 yards with ammo it liked and the worst group was still well under 75mm (3 inch).  Best group of the morning was using Magpul 115gr jacketed round nose kindly supplied by Gold Coast Shooting Supplies. This five-shot group of 43mm (1.7 inch) at 25 yards tells me there is huge potential here.

So all this goes to prove your mum really was right when she said, “don’t judge a book by it’s cover”. Sometimes the real beauty is just below the surface.

Bad news for NSW residents

SIG Sauer P320 review
The magazine is crimped to reduce capacity to 10 rounds in Australia

The SIG 320 is currently prohibited to NSW club shooters. Why?

Apparently the NSW Firearms Registry (FAR) believes the crimped, reduced 10-round magazines could be changed to the standard 17-round capacity. Anything can be done but I would not like to wreck magazines and face legal penalties for doing this, and I suggest FAR may be overreacting as many, many magazine makers use the crimp method to reduce magazine capacities.

The good news is that companies like Magpul in the USA are currently gearing up to make magazines for the 320 series and they are not the crimped style so later this year hopefully we may see the 320 reassessed for NSW if the importer changes to supplying the guns with polymer Magpul type ones.

This would be a very smart move and greatly increase the market for the modular magic of the SIG 320 in Australia.


  • Calibre: 9mm
  • Barrel length: 120mm
  • Magazine: 10 rounds (two supplied)
  • Frame: Polymer, full size
  • Trigger action: Striker
  • Sights: Steel, 3-dot, fixed
  • Overall length: 203mm
  • Weight: 836g
  • More info: SIG Sauer
  • Importer: Outdoor Sporting Agencies
  • Price: From around $865-900 (March 2021)



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  1. What you don’t mention is that most European Polymer semi-auto handguns including the SIG, do not like cast lead projectiles in terms of accuracy. Since most H Cagatory Club shooters reload and most use cast projectiles because of cost. It makes these guns almost useless because they are simply not accurate.
    If you have a look on the used guns website, they are full of second-hand European polymer pistols because the owners have found they just don’t shoot cast projectiles with acceptable accuracy.

  2. Rob, you raise an excellent point regarding Glocks and some other Euro pistols, however I have some great news for you.
    Whilst Sig is a Euro based company, the 320 model is actually designed and fully manufactured in the USA by SIG USA and as such they were fully aware of the US (and Aussie) desire for competitive shooters to use cast bullets as well as fully jacketed.
    When I tested the 320, I tried it quite extensively with my own handloads using Berry coated lead projectiles and they shot very well. I know a few guys putting high round counts through their own 320’s using exclusively cast projectiles and they have not reported any issues either.
    Hope this feedback is helpful


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