5.7x28mm

The 5.7x28mm is a small-caliber, high-velocity centerfire pistol cartridge that looks like someone shrunk a rifle round and stuffed it into a handgun — because that’s basically what FN did. It was developed in the late 1980s and early 1990s by Fabrique Nationale d’Armes de Guerre, better known as FN Herstal, in response to a NATO request for a new personal defense weapon system. The result was a bottlenecked, spitzer-type cartridge that moves fast, shoots flat, and fits in magazines that hold a lot more than you’d expect. It’s not a traditional handgun round. That’s the whole point.

FN developed the 5.7x28mm alongside the P90 personal defense weapon in the late 1980s, and NATO formally evaluated the combination in the early 1990s as part of their PDW trials. The round was designed specifically to defeat body armor at combat ranges — something conventional pistol cartridges simply cannot do. The military and law enforcement SS190 duty load is classified. The civilian versions are not, and they’re still fast enough to be impressive. The FN Five-seveN pistol followed the P90, putting the round in a handgun platform. Both firearms became icons. The 5.7x28mm is the only cartridge that made the leap from NATO PDW proposal to legitimate civilian cult status. Not many rounds can say that.

Standard civilian loads push a 40-grain projectile at approximately 1,750 to 2,000 feet per second depending on barrel length — out of the P90’s longer barrel you get more velocity, out of the Five-seveN pistol you still get figures that embarrass most handgun rounds. Muzzle energy runs around 340 foot-pounds, which sounds modest until you remember the bullet is tiny and moving extraordinarily fast. Trajectory is flat in a way that handgun shooters aren’t used to. Recoil is minimal — almost unsettlingly light for a centerfire cartridge. The high-capacity magazines the platform supports, typically 20 rounds in the Five-seveN, make the low recoil even more useful in practice.

Military and law enforcement use the restricted armor-defeating loads in P90s for close protection, vehicle crew, and special operations roles. On the civilian side, 5.7x28mm has carved out a devoted following among sport shooters who love the combination of high capacity, low recoil, and flat trajectory. It’s genuinely fun at the range in a way that’s hard to explain until you’ve shot one. Home defense use is debated — the round’s terminal performance on soft tissue with civilian ammunition is adequate but not the first choice of everyone. Where it absolutely shines is as a range toy and conversation piece that also happens to be capable. The PS90 and Five-seveN are two of the most interesting firearms available to American civilians, and the 5.7x28mm is what makes them work.

FN’s own P90 (the semi-auto civilian PS90 in the U.S.) and Five-seveN pistol are the originals and still the benchmark. Ruger added the 5.7x28mm to their lineup with the Ruger-57 pistol, bringing the cartridge to a wider audience at a lower price point. CMMG offers AR-pattern rifles and pistols in 5.7x28mm with their own magazine system. Diamondback Firearms, Kel-Tec with the P50, and several others have entered the space as the cartridge’s popularity has grown. It’s no longer an FN-exclusive ecosystem, which means more options and better ammo availability than the early days when you practically needed an FN catalog to keep the thing fed.

Against 9mm, the comparison is interesting. The 5.7 carries more rounds, shoots flatter, recoils less, and moves significantly faster. The 9mm hits harder in terms of raw energy from a standard defensive load and has decades of documented terminal performance data behind it. Neither is objectively better — they’re different tools. Against .22 WMR, a comparison people make because of the similar bullet diameter, the 5.7 is in a completely different performance class. The rimfire comparison is mostly a caliber-war argument starter. Against 4.6x30mm — the HK MP7 round that competed directly with it in NATO trials — the two are close enough that your choice of platform probably matters more than the cartridge. FN won that argument commercially. The 5.7 ecosystem is simply bigger.

Arms East stocks 5.7x28mm because the people who want it are exactly the kind of customers worth having — they know what they’re looking for, they’ve done their research, and they want to talk about it. The staff here has shot the Five-seveN and the PS90 and will give you an honest take on both. If you’re trying to decide between platforms, or you’re just trying to find ammo that isn’t sold out everywhere else, come in and have the conversation. This is the kind of round that rewards knowing the right store.