The world is changing before our eyes every minute of every day. New technologies propel industry forward with better efficiency, quality and end-user satisfaction. Having developed into somewhat of a curmudgeon by my late 20s, I have sometimes been dragged into accepting change for the past couple of decades. I’m one of those folks who usually likes the old ways better—such as cell phones with buttons, MP3 players just being MP3 players and typing search queries into a text box rather than calling out to an inanimate object on the kitchen countertop. I’m sure you can sense the irony.

No such hesitation exists, however, when it comes to the incredible advances made in the firearms industry. Granted, I, along with plenty of other folks, was dubious about mainstream polymer-framed handguns during their initial foray into the firearms industry. Those doubts quickly went away, and I learned my lesson. Now I’m proud to say that when I saw the introduction of the new Sig Sauer P320 RX, I was one of the first in line to try it out, and you might call me an early adopter. Baby steps.

The P320 RX is a new addition to Sig’s already popular line of pistols with polymer grip modules and interchangeable trigger control groups. Building on the success of the P320, Sig Sauer recently made some enhancements to the line, creating variants that are truly at home in a combat environment.

The main enhancement was the inclusion of a preinstalled reflex sight—Sig Sauer’s ROMEO1 model. The company’s second change was the incorporation of suppressor-height SIGLITE night sights that can be co-witnessed through the reflex sight’s optical window. But before we jump off into the deep end, let’s take a step back and survey the basic platform on which these changes were made.

The P320 Platform

Sig Sauer P320 RX Full-Size pistol rail
The P320 RX comes equipped with front cocking serrations as well as a long dust-cover Picatinny rail for mounting accessories like lights, lasers and combo units.

For the uninitiated, the Sig P320 was introduced around three years ago and immediately received enthusiastic reviews from shooters. Based on Sig Sauer’s P250 series of hammer-fired pistols, the company transformed the basic package into a striker-fired model that essentially kept the same lines and basic ergonomics of the original as well as its unique modularity.

The modularity of the P250 and the subsequent P320 is owed to the ingenious chassis that houses the trigger group and can be removed from one frame by the user and installed into a differently sized frame. The trigger group and accompanying chassis is the serialized component of the pistol. This is, in fact, the “firearm.”

This design allows the user to swap the chassis from a full-sized frame and slide used for home defense or competition to a subcompact frame for easier concealed carry. Currently, there are four basic frame sizes: Subcompact, Compact, Carry and Full-Size. These variations pretty much cover all of a user’s needs without having to purchase and register (in some jurisdictions) an entirely different pistol.

To match up with the different frames, Sig offers appropriate barrel lengths and magazines ranging from 10 to 21 rounds for the 9mm models. Other calibers are available for the P320, including the .40 S&W, .357 SIG and .45 ACP. The sample that I received for this test is in 9mm, so I’ll be speaking about the P320 RX in that context.

When you look at the specs for the Sig Sauer P320 on the company’s website, it’s a little confusing at first for new buyers. The specs list the frame as stainless steel and the frame finish as stainless steel, with a stainless steel slide. So, where exactly is the polymer? Remember that the trigger group module is what’s considered the firearm, so the specs you read are directly related to that piece of equipment.

What we would normally consider the frame is what Sig Sauer refers to as grip modules—almost as though they are accessories to the trigger group. And, in a way, they are, since they can be swapped out along with different barrels, slides and magazines.

The full-sized P320 comes with two full-sized, 17-round magazines and sports a 4.7-inch barrel, providing a long sight radius for quick targeting. The slide is finished in black Nitron finish and is available with either three-dot contrast sights or SIGLITE night sights.

Dressed up with its full-sized accoutrements, the P320 has an overall length of 8 inches, a height of 5.5 inches and a width of 1.3 inches. Despite the extra length, the weight of the full-sized P320 comes in at just 29.5 ounces unloaded.

Back To The P320 RX

Sig Sauer P320 RX Full-Size pistol romeo1 optic
The ROMEO1 can be adjusted for windage and elevation, and the CR1632 battery is loaded from the top, so the sight doesn’t have to be removed to install a fresh cell.

Part of the technological advances mentioned earlier has to do with the relatively new use of red-dot or reflex sights on handguns, particularly semi-automatic pistols. Where it used to take a skilled gunsmith to mill out a pistol’s slide to fit a reflex sight, many companies are now offering models with the slides pre-cut. Sig Sauer goes the extra step with the P320 RX by also mounting its ROMEO1 reflex sight so the package is ready to go straight out of the box.

The ROMEO1 is housed in a CNC-machined, two-piece magnesium assembly and is powered by a CR1632 battery. This battery is loaded from the top so the user doesn’t have to remove the optic and lose their zero in the process. The lens is made of aspheric glass that has an ultra-wideband coating to reduce reflections and glare, and to enhance light transmission for a crystal clear view of the target.

The ROMEO1 incorporates a 3-MOA red dot that has five daylight settings and two nighttime settings. Considering that 3 MOA is approximately 3 inches at 100 yards, at 25 yards, the red dot of the ROMEO1 covers just 0.75 inches—a very precise point of aim in comparison to normal iron sights. To make sure the sight effectively holds its zero, Sig Sauer utilizes two robust springs in conjunction with the carrier plate for the ROMEO1. Called TRUHOLD technology, the springs work in concert with the plate carrier to keep the optic from shifting during fire.

The ROMEO1 can be adjusted for both elevation and windage in 1-MOA increments, and it offers a 50-MOA range to make those adjustments. The ROMEO1 is waterproof to 1 meter and utilizes Sig Sauer’s MOTAC technology. This design activates the red dot when motion is detected and also turns off the power when no motion is detected for two minutes, helping to conserve battery life.

One issue I did dig into was the battery life of the ROMEO1. A concern I had were I to purchase an RX model was the constant motion of the gun while being carried in a holster. The unit would never turn off with the continuous daily movements of officers and concealed-carry holders carrying an RX model.

I contacted a Sig representative about this issue and learned that the battery life is 40,000 hours on medium brightness. That’s 4.5 years of continuous operation. Provided it lasts as described, the ROMEO1’s red-dot aiming system should be available whenever required, and the optic shouldn’t stay powered while on the go.

The P320 RX’s suppressor- height night sights provide an excellent sight picture and, as mentioned, can be co-witnessed through the lens of the ROMEO1. The iron sights include tritium inserts, making them a viable alternative to the reflex sight in low-light conditions. Throw in a threaded barrel and the Sig P320 RX is good to go as an excellent host for a sound suppressor.

Rockin’ At The Range

Sig Sauer P320 RX Full-Size pistol test
Thanks to the Sig ROMEO1 reflex sight, it was extremely easy to get on target quickly with the P320 RX, and it was very controllable off-hand—even with hotter +P loads.

Having purchased a base P320 a couple of years back, I felt like I already had a good idea of how things were going to go when I broke in the new P320 RX. Sig Sauer is known for its quality and consistency, and I wasn’t expecting any surprises. My own personal copy is extremely accurate, and in the two years I’ve had with it, I haven’t experienced a malfunction yet.

That said, the inclusion of the ROMEO1 reflex sight on the P320 RX adds a whole new dimension to the shooting experience. With the ability to focus on the red dot “painting the target” in the lens, it’s much easier to get fast, accurate hits at longer distances, and it’s less taxing on the eyes than having to align iron sights to try and achieve the same results.

I will admit that the trigger on the P320 RX is not the lightest I’ve tried. My test sample’s broke at 6.25 pounds, but it was a clean break (I especially appreciate the metal trigger) and had a short reset for quick follow-up shots. Also, the P320 pistols are among the most natural-shooting pistols for me because of the reach from the backstrap to the trigger. It fits my hands flawlessly for a smooth and natural pull, though the fit will vary depending on the person.

Shooting from a rest at 25 yards with the P320 RX provided some excellent results. I used Sig’s own 115-, 124- and 147-grain V-Crown JHP loads as well as a box of Federal’s 147-grain +P HST rounds to keep it honest. All four loads performed more than well enough to serve for self-defense or duty, though the P320 RX did have its favorites.

The best five-shot group of the various loads came with Sig’s 124-grain V-Crown JHPs at just 1.25 inches at 25 yards. The best average group size, however, went to the 147-grain V-Crowns with an average spread of 1.79 inches. While these results seem too good to be true, the 0.75-inch coverage of the ROMEO1’s red dot at 25 yards provides a very precise aiming point.

In addition to the premium loads that I used during the range sessions, I also fired an additional 300 rounds of both Sig and Federal 115-grain FMJs during different drills to test for reliability. As expected, the P320 RX digested all of the FMJs and hollow-point loads without a single hiccup. This performance reinforced my previous experience with the P320 platform and its efficacy, accuracy and absolute reliability.

Seal Of Approval

Sig Sauer P320 RX Full-Size pistol army
In early 2017, the U.S. Army selected the P320 Carry (left) with a full-sized slide option (right) to replace its legacy Beretta M9 pistols.

After much testing, the United States Army just announced the selection of the P320 line as the new M17 service pistol, and that choice is going to hold more sway than any recommendation I could give. Even so, I’ve had the chance to shoot a base P320 and both the P320 RX and P320 RX Compact, and I have to mention the incredible consistency between the samples in terms of accuracy, trigger pull and reliability across the board.

In bringing out the P320 RX, Sig Sauer took an excellent pistol platform and made it that much better. The addition of the ROMEO1 reflex sight and
suppressor-height night sights to the mix makes it a more versatile and effective weapon. Faster, more precise aiming is always welcome, particularly on a combat handgun, and Sig Sauer’s P320 RX is a package that’s just as ready for the streets as it is for active duty.

Caliber: 9mm

Barrel: 4.7 inches

OA Length: 8 inches

Weight: 29.5 ounces (empty)

Grip: Polymer

Sights: SIGLITE night, ROMEO1 reflex

Action: Striker-fired

Finish: Matte black

Capacity: 17+1

MSRP: $869

For more information, visit

This article was originally published in “Combat Handguns” July/August 2017. To order a copy, visit

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