FN 5.7 x 28mm Round, Explained

The FN 57x28mm Round pictured.
| February 13, 2023
Categories: Assorted Ramblings
Although it has been around for nearly 30 years, the FN 5.7 x 28mm round has become increasingly popular among shooters for personal defense, light varmint hunting, and casual target shooting.


Fabrique Nationale Herstal (FNH or FN) developed the 5.7x28mm round in the late 1980s for use in the FN P90 Personal Defense Weapon (PDW). The intent was to develop a high-velocity round to replace the 9mm Parabellum for NATO.
An FN pistol pictured.

The pistol for which the FN 5.7 x 28mm round was created. (Photo credit: FNH)

While some have compared the round to 22 Magnum or 22 Hornet, it is completely different. Unlike most common types of ammunition, it has no parent case. FNH designed it from the ground up for its purpose.

When first introduced in 1990, the round was designated SS90 and fired a 23-grain plastic core bullet with a muzzle velocity of 2800 feet per second (fps) from the 10” barrel of the FN P90. It should be noted as a general rule across ammunition types that when fired from a shorter 6” BBL pistol the loss in velocity is about 200 fps. When using a 16” carbine, the velocity increased by 300 fps.

Three FN 57x28mm Rounds, one with a metal tip and two with polymer tips

In 1993 an improved version debuted, known as the SS190. To chamber the 33-grain bullet in a pistol, the FN Five-SeveN, it’s seated slightly deeper. It used a steel and aluminum core instead of the original plastic one. SS190 supplanted the original SS90 round.


According to NATO tests, the round proved superior in performance to 9mm Parabellum. The recoil is 1/3 of that of the 9mm. Additionally, the rounds weigh 1/3 less of a 9mm cartridge and theoretically allow troops to carry more ammunition.
Penetration of various materials, including soft body armor, left 9mm in the dust. Viewed as a self-defense round within a military context where a hollow point or expanding ammunition types were against the protocols of the Hague Convention, over-penetration was not bad. The P90 was definitely on track as the latest next-generation PDW for support troops and personnel. They may not have needed a full-sized service rifle, but maybe something more powerful with a greater feed capacity than a typical service pistol.
FN states the round’s ideal range is within 250 yards with a maximum range of 1800 yards from the P90. Out of a pistol, this changes to about 50 yards with a maximum of 1500 yards.
FN coats the rounds in a thin layer of polymer to aid in feeding, case extraction, and ejection. This greatly helps with regard to reliability.
In addition to numerous military units, many law enforcement agencies, including the Secret Service, selected both the P90 and FN Five-SeveN.

Non-Military Roles

On the civilian side, the FN 5.7 x 28mm round has proven very popular over the past 15 or so years. FN had to redesign the P90 to meet importation standards in the US. FN lengthened the barrel to meet requirements without running afoul of National Firearms Act (NFA) restrictions.
Perhaps even more popular are the handguns chambered in 5.7, such as the original FN Five-SeveN and Ruger’s Model 57. Several manufacturers offer AR-15-style rifles and upper receivers chambered in 5.7 x 28mm. Some use the original 50-round magazine of the P90 or its civilian counterpart, the PS90. Newer incarnations use the pistol magazines of the FN Five-SeveN pistol, and perhaps the Ruger pistol magazine may be offered in the future.


The biggest complaints from shooters have been both the cost of ammunition and the lack of support on the reloading side. Pre-pandemic, a 50-round box of 5.7 ammo cost between $20 and $30. Over the past year, the price has soared tremendously. In time, the price should come down again, but this has never been an inexpensive round to shoot.
A major concern regarding a pistol chambered in 5.7 is the risk of overpenetration in a civilian defensive situation. This risk may be overhyped, however, as the bullet does not retain much energy due to its light weight while passing through a solid target. In fact, it carries less than half the energy of a typical 9mm bullet beyond 200 yards.
A box of FN 5.7 x 28mm rounds

(Photo credit: FNH)

While not intended as a hunting round beyond its use on small varmints, some rounds are loaded with a 40-grain Hornady V-Max bullet with a polycarbonate tip that aids in expansion.


Whether you collect military-style firearms or are simply a fan of a high-performing, somewhat specialized round, the FN 5.7 x 28mm may have something to offer you as a shooter. It is important not to downplay or overplay its performance, but rather to keep in mind the purposes for its design. 


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