5.7×28 Ammo: Ballistics, Loads and Barrel Length

It was built to replace 9x19mm Parabellum in personal defense weapons and pistols. NATO’s requirement, often traced to document D/296, asked for more range, more accuracy, and better terminal performance than 9mm, plus the ability to defeat the soft body armor of the era. The intended users were not riflemen. They were vehicle crews, support troops, and other second-line personnel who needed something more capable than a pistol and more compact than a full-size rifle.

FN answered with a complete system: the cartridge, the P90 bullpup PDW, and later the Five-seveN pistol. The first production load, SS90, used a 23-grain polymer-core bullet at roughly 2,800 fps from the P90. That projectile did not last. In 1993–1994 it was replaced by the SS190, a roughly 31-grain steel-and-aluminum-core FMJ designed to defeat a NATO CRISAT target (1.6 mm titanium plus 20 layers of Kevlar) and then yaw in tissue. From the P90, FN has long claimed the SS190 will perforate 48 layers of Kevlar out to 200 meters; from the Five-seveN pistol, the same claim is made to about 50 meters.

That military duty load is restricted. In the United States it is not sold to civilians. Commercial 5.7x28mm ammunition uses conventional lead-core or lead-free sporting and defensive bullets. Those commercial loads are not the SS190, and they should not be described as if they were.

• Give a compact weapon more reach and a flatter trajectory than 9mm
• Defeat Cold War–era soft armor with a dedicated military projectile
• Cut recoil and cartridge weight so a soldier could carry more ammo and shoot faster
• Share one cartridge between a pistol and a PDW

It never replaced 9mm as NATO’s general sidearm cartridge. It did carve out a durable niche, and after FN’s patents expired the commercial market exploded: Ruger-57, Smith & Wesson M&P 5.7, PSA Rock, KelTec P50/R50/PR57, CMMG, and others.

A complete 5.7x28mm cartridge weighs roughly half as much as a 9mm cartridge. Recoil is commonly described as about two-thirds that of 9mm, or less, depending on the gun and load. Magazine capacity follows from the skinny case: 20–23 rounds in most pistols, 50 in P90/PS90 magazines.

Remeber to treat every published velocity as barrel-specific. A “2,000 fps 5.7” figure is usually a carbine or P90 number. Out of a 4.8-inch pistol, the same 40-grain sporting load is closer to 1,650–1,750 fps.

Trajectory is the cartridge’s real party trick. A 40-grain bullet at pistol velocity, zeroed at 25 yards, is typically down about half an inch at 50 yards and around 4–5 inches at 100 yards. From a P90 or PS90, drop to 100–150 yards is much smaller. Compared with 9mm, the 5.7 stays flatter and arrives sooner. Compared with 5.56, it is still a short-range cartridge. Effective practical range is about 50–75 yards from a pistol and 150–200 meters from a PDW with duty ammo.

Ballistic coefficients for common 40-grain bullets sit around G1 0.20. The 27-grain open-tip loads are closer to 0.12. They start faster and bleed speed sooner. That is why a 40-grain V-Max or TMJ is often the better 100-yard choice even if a 27-grain load looks hotter at the muzzle.

Energy numbers look modest next to 9mm. A 115-grain 9mm can leave a pistol with 350–400 ft-lb. A 40-grain 5.7 from the same length barrel is often 240–270 ft-lb. The 5.7 argument was never raw energy. It was velocity, sectional density of a skinny bullet, magazine capacity, recoil, and with the restricted SS190 compared to armor performance the 9mm ball load of the 1980s could not match.

Commercial 5.7 behavior in tissue depends on bullet construction and impact velocity.

• 40-grain V-Max (SS197SR and similar): Polymer tip drives rapid expansion or fragmentation on light game and gel. Excellent varmint bullet. Defensive results vary with velocity; from a pistol it can expand or come apart early.
• 40-grain bonded JHP (Speer Gold Dot, and similar defensive loads): Built to expand at 5.7 pistol speeds and hold together. This is the load class most often recommended for carry.
• 27-grain aluminum-core open-tip (SS195LF / SS198LF): Often looks like a hollow point but behaves more like an open-tip match bullet. At pistol and PDW velocity these rounds commonly yaw and tumble rather than mushroom. Gel tests frequently show dramatic upset and relatively modest penetration.
• 40-grain FMJ/TMJ (American Eagle, Fiocchi Range Dynamics, FN GUNR): Training bullets. They tend to penetrate more and expand less. Not the first choice for defense.
• SS190 (restricted): Designed to punch CRISAT/IIIA-class soft armor, then yaw. Soft-tissue penetration is often cited in the 11–13.5 inch range after armor, which is why FN marketed limited over-penetration as a feature. It is not a civilian load.

SS190, SS191 tracer, and official subsonic/frangible duty loads remain military and law-enforcement items. If a box does not say SS190 and is sitting on a civilian shelf, it is not the armor-piercing service ball FN built for the P90.

Handloading is possible with .224 bullets and small-rifle primers. The case is charge-sensitive and overall-length sensitive. Most experienced loaders stay at or under 40 grains for pistol-length barrels; the 1:9 twist will stabilize heavier bullets, but the tiny case does not give them much to work with.

• 4.8–5.3 inches: Pistol ballistics. 40-grain loads in the mid-to-high 1,600s fps. 27-grain loads from about 1,900 to a bit over 2,200 fps depending on the recipe. Fine for 25–50 yards. Recoil is soft. Muzzle blast is sharp.
• 8 inches: The first length where the cartridge starts to feel like a PDW instead of a hot .22. Expect a few hundred feet per second over a Five-seveN with the same ammo.
• 10.4 inches (P90 / PS90 SBR): The design length. This is where FN generated its original duty numbers. Independent chronograph work on a 10.4-inch PS90 SBR has shown SS197 around 2,022 fps and SS198 around 2,431 fps. SS190 in that test ran 2,279 fps.
• 16 inches: Maximum practical velocity for commercial powders in this case. FN’s PS90 figures put SS197 at 2,034 fps and 368 ft-lb. Light bullets can pick up another 150–300 fps versus the P90, depending on the load. Past 16 inches the returns flatten.

Barrel length also changes terminal performance. Expansion and yaw thresholds are velocity-dependent. A defensive hollow point that opens from a 16-inch carbine may be marginal from a short pistol. Conversely, a fragile V-Max that fragments too early from a carbine may hold together better from a 5-inch barrel. Match the load to the gun, not just the caliber.

Twist is usually 1:9. That is enough for the 27- to 40-grain bullets the cartridge was designed around. Very heavy subsonic slugs are a different stability problem and a different ballistic problem.

Use 5.7x28mm for what it does well.

It does well as a high-capacity, low-recoil pistol cartridge with a flat 50-yard trajectory. It does better as a compact carbine or PDW cartridge, where the extra barrel finally uses the powder FN put in the case. It is a legitimate varmint and small-game option with V-Max-style bullets. It is a niche defensive option if you pick a modern expanding load and accept that you are not shooting 9mm energy or 5.56 rifle energy.

It is not a general-purpose rifle cartridge. It is not civilian armor-piercing ammo. It is not cheap 9mm practice ammo, even though prices have fallen from the old dollar-a-round era into a more workable range-ammo band. And a velocity quoted without a barrel length is not a velocity. It is marketing.

If you remember only one thing from the ballistics, remember this: 5.7x28mm was built as a system. The cartridge, the 10.4-inch P90, and the restricted SS190 load were meant to work together. Everything else including pistols, 16-inch carbines, 40-grain sporting ammo, Gold Dots,  is an adaptation of that system. Judge each combination on its own numbers, not just on the legend of the P90.