5.7mm vs 9mm: More In Common Than You Might Think

The introduction of the Ruger 57 sparked renewed interest in the 5.7x28mm round. FN created 5.7mm to be a defensive round for the military, primarily for pistols and smaller personal defensive weapons. This, coincidentally, is almost the exact same niche filled by the 9x19mm cartridge, one of most-popular rounds on the market today. So what (if any) are the advantages of 5.7 vs 9mm? 

A Brief History of 9mm Ammunition

We often call 9x19mm ammo “9mm Luger”, and for good reason. The German Army wanted a round with a little more punch, so George Luger expanded the neck of his existing 7.62x21mm cartridge to make a 9mm diameter round. The P-08 Luger pistol and the 9mm Luger (aka 9mm Parabellum) soon became sought-after icons of World War 1, and later, World War 2. 

Second-line soldiers soon adapted the Luger pistol to serve a second purpose, as a defensive firearm. The “Artillery Luger” featured a longer barrel and higher capacity magazine, along with a detachable stock that, in effect, turned the pistol into a carbine. This, in turn, gave second-line troops a more effective defensive option that works at longer ranges. 

In addition, one of the first effective submachine guns, the German MP18, used the 9×19 Parabellum round. The 9mm cartridge grew in popularity after World War 1, and even more so after World War II. It’s now one of the most popular pistol cartridges in the world. It is the standard pistol cartridge for a large portion of the world’s armies, as well as the standard NATO pistol round. 9mm became the standard pistol round for the U.S. military in 1985, when it, along with the Beretta 92FS, replaced the iconic 1911 pistol, chambered in .45 ACP. 

A History of 5.7mm Ammo

The widespread military use of 9mm began to show some of its weaknesses. 9mm is an effective pistol cartridge and is also a very popular submachine gun cartridge. However, 9mm was designed before the First World War, an environment where modern innovations like bullet resistant body armor were not in common use. 

The increased use of body armor during the Cold War drove interest in ammunition that could punch through bullet-resistant materials, such as the M855 5.56mm rifle round. While 9x19mm is effective on unarmored targets, basic body armor easily stopped it. This drove interest in developing a cartridge for pistols that would be more effective versus body armor than the 9mm round. 

Mil-Spec Ammo

Enter the 5.7x28mm round. Fabrique Nationale created 5.7mm in response to a NATO requirement for a combination of cartridge and firearm second-line troops in the field could use. At first, that sounds like the exact same reasons why the “Artillery Luger” was created. It is. However, there was one significant difference in the new specifications. The NATO requirement was for a cartridge that could penetrate Level IIIA body armor at a distance of 200 yards. As Level IIIA is specifically designed to stop the 9mm round, a new kind of cartridge was needed. Belgium’s FN Herstal created the 5.7x28mm round, along with the FN Five-SeveN and PS90 firearms to shoot it.

Today, 5.7mm armor-piercing rounds are not available to the general public. As such, we’re going to compare some of the 5.7mm ammunition that is available for sale and see how it stacks up against 9mm. What are some of the advantages of 5.7 vs 9mm? What are the disadvantages? 

Advantages of 9mm

Almost universal acceptance and a 70 year head start on 5.7 has made 9mm one of the most commonly available calibers today. Ammunition manufacturers around the world make a dizzying variety of 9mm ammunition. There are also 9mm pistols in every corner of the world, in every shape and size. 

Because of this popularity, 9mm is cheap compared to other centerfire pistol rounds. There are usually many different kinds of ammo available at any given moment.

9mm is also an effective defensive round. Bullet technology has improved to where 9mm hollow point ammunition enjoys a proven track record. Millions of gun owners trust it around the world.

Advantages of 5.7mm

The big advantage is speed, and lots of it. The 5.7mm round uses lighter weight bullets than a round of 9mm. Rather than shoot a 115 grain 9mm round at around 1100 FPS, the 5.7mm fires 40 grain rounds that scoot out of the barrel at around 2300 feet per second. 

FN designed 5.7mm rounds with a ballistic profile that is more similar to a rifle bullet than a pistol bullet. A 5.7mm has a pointed tip and boat-shaped tail which help it cleave through the air, increasing its effective range.

The diameter of 5.7 vs 9mm makes a difference inside the pistol. A round of 5.7mm is less than 2/3rds the diameter of a round of 9mm. This means you can stack more of them inside a magazine. This in turn means more rounds inside the magazine of your pistol.

Disadvantages of 9mm

9mm is not a round designed for longer distances. The shape of the nose is round, and the bullet looks a bit squat when viewed in profile. This is not a shape that is optimized for long-range shooting. For that reason, we use most long guns chambered in 9mm in close quarters combat, not at longer ranges. 

Disadvantages of 5.7mm 

5.7mm is the new kid on the block. Because of this, there is not the wide variety of ammunition available for it compared to 9mm. In addition, the best ammunition for it, the SS190 armor-piercing round, is not available for sale to armed citizens. The SS190 is considered to be “armor-piercing,” and that’s a no-go for armed citizens, says the ATF. On top of this, the cost per round of 5.7 vs 9mm is higher by about 10%, which translates into less bang for your buck (literally). 

Comparing 5.7 vs 9mm Ammo

As said earlier, a pistol chambered in 5.7mm will have more rounds in its magazine than a comparable pistol chambered in 9mm. Recoil will also be lighter with 5.7 vs 9mm. Those two facts put together make a compelling argument for using a 5.7mm pistol as a defensive firearm. But just how effective is 5.7 vs 9mm? We’ll shoot two guns, a 9mm CZ75 and a 5.7mm Ruger 57, and compare them in three different areas. We will also shoot two different kinds of ammo in each pistol, one full metal jacket round and one defensive round. We measured the velocity of each round with a Pro Chrony chronograph in order to determine the actual muzzle energy of each round.

9mm Fiocchi 115 Grain Full Metal Jacket
Average muzzle velocity: 1132 fps
Average muzzle energy: 327 fps

9mm Sig Sauer 124 Grain Jacketed Hollow Point
Average muzzle velocity: 1151 fps
Average muzzle energy: 365 ft/lbs

5.7mm FN 30 Grain SS195LF Jacketed Hollow Point
Average muzzle velocity: 2162 fps
Average muzzle energy: 311 ft/lbs

5.7mm American Eagle 40 Grain Full Metal Jacket
Average muzzle velocity: 1653 fps
Average muzzle energy: 243 ft/lbs

The velocity of a 5.7mm round might be much higher than a 9mm round. However, the lighter weight of the bullet means that it doesn’t deliver the same amount of energy on-target that a round of 9mm does. 

Recoil

The 9mm round isn’t known for it’s recoil, and the full-size metal CZ75 helped control what little recoil there was. However, even the soft recoil of a 115 grain round in a full-size, metal-framed pistol is more than the recoil from the Ruger 57.  As you can see from the photos below, recoil from the CZ75 was mild, but it was even milder with the Ruger. 

Gel Testing 

To test the defensive capabilities of 5.7 vs. 9mm, we shot five examples of each round into Clear Ballistics gel. The current FBI standard for defensive ammunition is that an effective defensive round should penetrate four layers of heavy clothing, then go through 18 to 24 inches of ballistics gelatin. To follow these protocols as closely as possible, we covered the front of the gel with four layers of heavy cloth and then shot the gel from 10 feet away. 

Results

Five rounds of 124 grain 9mm Sig Sauer JHP
Shot 1: 23.125 inches of penetration
Shot 2: 23.25 inches of penetration
Shot 3: 21.125 inches of penetration
Shot 4: 21 inches of penetration
Shot 5: 17.125 inches of penetration

Average penetration: 21.125 inches

30 grain 5.7mm FN JHP
Shot 1: 10 inches of penetration
Shot 2: 10 inches of penetration
Shot 3: 9.5 inches of penetration
Shot 4: N/A
Shot 5: N/A  

Average penetration: 9.83 inches

Results

We found all of the recovered 5.7mm rounds in the gel with their bases toward the direction of motion. This indicated that they were tumbling as they passed through the testing medium. The tumbling motion increases the temporary wound channel of the ammo. This is something quite common in rounds with the same profile as our testing ammo. Because of this tumbling motion, two of the fired rounds flew out of the gel. We chose not to include them in the results. All three rounds we recovered from the gel failed to expand. In addition, the tumbling dramatically slowed each round inside the medium. This caused them to slow down well short of the FBI’s minimum standard of 16 inches of penetration.

On the other hand, the 9mm Sig Sauer ammunition all penetrated to 16 inches, and a bit beyond. The average penetration of this round exceeded the FBI standard. All of the rounds expanded inside the gel. We successfully recovered each of them from inside the gel block. 

Armor Penetration

One of the reasons NATO saw the need to replace 9mm with something else was improved performance versus Level IIIA body armor.

Level IIIA body armor is designed to prevent penetration from pistol rounds and 12 gauge buckshot rounds. As Level IIIA is specifically designed to stop 9mm rounds, we chose not to test it. However, we tested the 5.7mm rounds to see if they would go through body armor. We set up two panels of body armor in front of a block of ballistics gel. Then, we shot at each panel with one round of 5.7mm ammo. We shot the first panel, on the left of the photo, with one round of 30 grain SS192 ammo. This is a hollow point, copper jacketed and aluminum cored ammo that was purchasable by armed citizens. It is now discontinued. 

We fired one round of 30 grain S195LF at the second panel.

Results

Neither 5.7mm round was able to penetrate the Level IIIA plate. In theory, the 5.7mm round may be capable of piercing pistol-rated body armor. However, not with ammunition that is available to the gun-buying public. 

Conclusion 

The recent introduction of the Ruger 57 pistol has jump-started interest in the 5.7mm round. There are certainly some advantages of 5.7 vs 9mm, such as a larger capacity magazine and a flatter recoil. However, if you choose 5.7mm, you’ll need to realize that it may not penetrate far enough into the target to reach a vital area and stop the threat. This means you must pay close attention to where your shots are landing and be prepared to switch over to a failure to stop drill at a moment’s notice if things aren’t going well.

9mm may not have the cool factor that 5.7mm has, but it’s been a proven performer for over 100 years now and costs less per round. 9mm has more recoil than 5.7mm, but it also has a wide selection of defensive ammunition that have proven to do the job. 

As for me, I really enjoyed shooting the Ruger 57. However, when it comes to personal defense, I rely on a 9mm pistol, a Smith & Wesson Shield, to do the job of protecting me and my loved ones.