GUN REVIEW: Sig Sauer P320 .40 Caliber

Sig Sauer’s first polymer-frame, striker-fired handgun

By Warren Wilson

There are three things I thought I’d never see in my career: Cappuccino in the drink holder of a police car, Captain Kirk’s Phaser on a cop’s duty belt, and a polymer, striker-fired Sig Sauer pistol. Thanks to Sig’s recent introduction of the P320, I’m now 0 for 3. Sig Sauer is probably not the first manufacturer that comes to mind when you think about plastic guns. They’ve dabbled in this area with their P250 and a few other models, but are now fully attacking the market with their new P320 Nitron. It was introduced at the 2014 SHOT Show and law enforcement officers anxiously gathered at the Sig Sauer display to handle the new pistols and speak with Sig’s representatives.

There were a lot of firearms to ogle and handle, but the P320 was the main attraction for several attendees including yours truly. One of my family’s ‘community’ guns is a Sig P250 Compact chambered in 9mm. The P250 is a polymer-framed, hammer-fired pistol with a trigger system similar in feel to a revolver. My wife, daughter and I all like to shoot this model and it’s a great handgun for new shooters on which to learn. The P320 is very similar to the P250, but instead of having a hammer, it features a striker fire system. Like its predecessor, the P320 comes in both full-size and carry (compact) models.

“Nitron” refers to the blackened finish on the steel slide of the gun. The first thing I noticed when handling the P320 was its ergonomics. Perhaps that term has been beaten to death, but it’s appropriate in this case. The gun feels really good in the hand. Its second and most obvious attribute is the semi-auto’s trigger. I hate to throw around the word “best,” but this pistol truly has a great trigger. It feels crisp, short, and about as light as you’d want for a duty pistol. I was pleasantly surprised by how good it was. Sig’s website lists the P320’s trigger weight at between 5.5 pounds and 7.5 pounds. It feels lighter than that. In fact, if you’d asked me before I broke out my RCBS trigger scale, I would’ve said it was less than 5.5 pounds. That was also the opinion of the half-dozen or so officers who ended up handling the gun. As a matter of fact, it measured between 6.7 and 6.9 pounds on the trigger scale. I was more than a little taken aback. I started to think there was something wrong with my trigger scale. But there wasn’t; Sig just did something really right with the bang lever on this pistol.

The P320 Full-Size Nitron is available in your choice of either 9mm, .357 Sig or .40 caliber, with a .45 ACP offering promised in the near future. Its magazine capacity is 17 rounds in 9mm and 14 rounds in .357 and .40 caliber. The P320 Carry Nitron magazines hold 15 in 9mm and 13 in .40 caliber and .357 Sig. The Full Size pistol weighs in at 29.4 ounces while the Carry comes in right at 26 ounces. Slide stop levers are on both sides of the frame and the magazine release is reversible for our “right-minded” friends of the left-hand persuasion.

Here’s the fun part about these pistols: You can buy both the Full Size and Carry models individually, or just one of the complete pistols and the parts package of the other. Then you will have a single trigger package, as well as the slides, barrels, frames and magazines of both the Full-Size and Carry versions of the Nitron. The trigger package is the actual gun as far as the law is concerned. It has the serial number and is the only part that requires an FFL transfer. There is only one serial number to register with your department. It would not be unreasonable for an officer to carry the Full Size during his/her regular shift, take a minute (not an exaggeration) to disassemble the Full Size pistol, install the trigger package in the Carry frame, and then reassemble with the Carry parts before leaving on off-duty pursuits. Extra slides, grip frames, and even calibers can be shipped directly to you since they’re not serial numbered firearms parts.
The P320 has an accessory rail, Siglite Night Sights, and comes in a choice of three different grip sizes. Speaking of grips, there will be no need to send a P320 off for stippling or adding skate board tape as is so common with some other similar polymer pistols. The front strap, back strap and both side panels are textured enough to allow the shooter an excellent purchase of the gun right out of the box.

Field stripping this pistol is a breeze. There is no need to pull the trigger or use a tool to deactivate the sear. The P320 does not allow disassembly of the pistol while a magazine is seated. Just lock the slide back, flip the take-down latch, and remove the slide assembly forward off the frame. Keeping pressure on the back of the captured recoil spring and guide, pull it upward and off the barrel. The barrel will then come out the front of the slide. Pulling the guide rails forward and upward frees the trigger package. The obsessive (but still lazy) gun-cleaning troll that lives in my head loves this system. It allows for the thorough cleaning of a detail strip while only exerting the effort it takes to conduct a field strip. Reassembly is the same in reverse with one exception. After putting this pistol back together, the slide must be locked back and the slide stop pushed upward to disengage the aforementioned magazine safety. A shooter unaccustomed to this step and unwilling to carefully read the instructions may spend several minutes staring confused at the P320 like a Chimpanzee looking at a Rubik’s Cube. Of course, that could never happen to a Police Marksman reader…
or writer.

Range Time
I fed the P320 over 100 rounds of .40 S&W caliber Federal 155-grain HST, 50 rounds of Corbon 150-grain JHP, and around 100 rounds of a mixed bag of factory full-metal jacket rounds over two days without cleaning. The slide failed to lock back twice on an empty magazine for another 1911 shooter and myself. Many of us who are cursed with the 1911 addiction tend to hold down on the thumb safety as an index point while firing. Most Sig pistols’ slide stop/release levers are in the same general position as the aforementioned thumb safety. This downward pressure makes it impossible for the slide stop to engage. It should also be noted that my thumbs are as long as that of a lower primate and cause similar interference with many other well-regarded
defensive handguns.

When I focused on not putting pressure on the slide stop, all was good and the pistol locked back appropriately. Discounting that, the P320 functioned perfectly with all loads. It grouped just about an inch and a half to the right at 25 yards, but hitting an IPSC steel target at 50 yards was almost effortless. Over three days, four officers shot the P320. A few of us were able to get 2.5-inch groups at 25 yards with Federal 155-grain HST, Corbon 150-grain JHP, and Federal American Eagle FMJ without the aid of a mechanical rest, sandbag or sub-100-degree temperatures. That is well within what Police Marksman Magazine legend Evan Marshall refers to as, “minute of felon,” which is a tongue-in-cheek description of the minimum allowable level of accuracy for a duty-grade pistol or rifle. The Corbon loading averaged 1,235 feet per second while the HST averaged 1,167 fps.

A Winner On All Counts
To paraphrase my grandfather, this thing is slicker than grease on a doorknob. With an MSRP between $669 and $713, the “street price” of these pistols is right in line with other striker-fired duty pistols. However, there is an obvious economical advantage with the modular system inherent in the P320. You can get two guns for about two-thirds of the price you would normally pay for the pair when you purchase a P320 Full Size and a P320 Carry frame package that is currently available. With this pistol, Sig Sauer is aggressively and unapologetically stalking the law enforcement market. The P320 has all of the good qualities police officers like in polymer guns, plus a few more. Three other officers shot this pistol while I had it for test and evaluation and each of them used the word, “sweet.” Sometimes, the simplest terms are the most descriptive. PM

Warren Wilson is a Lieutenant with the Enid Police Department in Oklahoma. He is a former SWAT team member/leader and has been in law enforcement for 17 years.


  1. Sig Sauer introduced the P320 Full Size and P320 Carry at the 2014 SHOT Show.
  2. The P320 comes with two magazines, a polymer holster, and a gun lock.
  3. The P320 Full Size pictured next to the author’s P250 Compact.
  4. A 25-yard 2.5-inch group with Federal 155-grain HST ammunition.
  5. The P320’s modular design is simple to field strip. The serial numbered trigger group is the “gun.”
  6. Seven rapid-fire rounds at 7 yards.
  7. The Sig P320’s striker-fired trigger is the same pull from first shot to last, making it an excellent choice for police work.

Back to Top