5.7x28 vs 9mm: Is FN's Little Round Worth the Premium?

A replacement for 9mm that 9mm outlived

In the 1980s, NATO asked a question that sounds odd now: what should replace the 9mm? Body armor was spreading, and a pistol-caliber round that couldn't get through it worried military planners. FN Herstal's answer was a tiny bottlenecked cartridge built around a 0.224-inch bullet, essentially a scaled-down rifle round. Designers Jean-Paul Denis and Marc Neuforge worked on it from 1986 to 1990, and it debuted with the P90 personal defense weapon.

NATO trials in 2002 and 2003 put the 5.7x28 up against Heckler & Koch's 4.6x30. The NATO group recommended FN's round, Germany objected, and standardization stalled until 2021. Meanwhile, 9mm stayed in nearly every holster on Earth.

Then something unexpected happened. Civilian 5.7 pistols multiplied. The Ruger-57 arrived in late 2019, followed by Smith & Wesson's M&P 5.7, Palmetto State Armory's 5.7 Rock, Kel-Tec's P50 and more. A cartridge built for armor became a hit at the range. So is it worth buying into?

The two rounds at a glance

Dimensions and the recoil comparison come from the cartridge's reference entry; capacity for the Five-seveN comes from its specifications.

Velocity vs weight

The 5.7's headline is speed. FN's published figures, as summarized in the cartridge's reference entry, put the 40-grain V-Max load (SS197SR) at about 1,950 fps from the P90's longer barrel and roughly 60 meters per second slower from the Five-seveN pistol. Hornady lists its 40-grain Critical Defense 5.7 load at 1,810 fps from a 4.8-inch test barrel, for 291 ft-lb of energy.

Compare a common 9mm defensive load. Hornady's 115-grain Critical Defense is listed at 1,135 fps from a 4-inch barrel and 329 ft-lb. A Federal HST 147-grain load is listed at 1,000 fps and 326 ft-lb.

So on paper, a quick 5.7 load and a 9mm defensive load land in the same energy neighborhood. They get there in opposite ways: the 5.7 throws a light bullet very fast, and the 9mm throws a heavy bullet at moderate speed. Light, fast bullets shoot flatter and recoil less. Heavier bullets carry more momentum and have a longer, far deeper body of real-world defensive data behind them.

What the 5.7 does genuinely well

• Low recoil. The muzzle stays flatter, which helps fast follow-up shots and makes the gun friendly to recoil-sensitive shooters.
• Capacity. Twenty rounds in a full-size pistol, from a slim bottlenecked case, is a real advantage.
• Flat trajectory. At longer pistol distances, high velocity means less holdover.
• Fun. That's a legitimate reason to buy a range gun, and 5.7 owners tend to say so.

Where 9mm still wins

• Ammo selection. Walk into any store and 9mm is there in FMJ, hollow points from every major brand, and specialty loads. Our 9mm bullet weight guide shows how wide that menu is.
• Defensive track record. Modern 9mm hollow points have been refined through decades of law-enforcement evaluation. 5.7 civilian defensive loads have a far smaller body of work.
• Gun choice. Micro-compacts, duty guns, carbines, competition pistols. Almost every pistol maker builds a 9mm.
• Running cost. 5.7x28 ammunition has historically cost more per round than 9mm, often by a wide margin. Check current price before you commit to a platform.
• Noise and flash. Reference sources note the 5.7's loud report and considerable muzzle flash, which matters indoors.

The armor-piercing confusion

The 5.7's military reputation comes from the SS190 load. The ATF classifies it as armor-piercing handgun ammunition, and FN restricts it to military and law-enforcement buyers. The loads civilians can buy are different. FN's commercial SS195LF hollow point and SS197SR V-Max, and the 5.7 loads from Hornady, Speer, Fiocchi and others, are not the SS190.

That means the civilian 5.7 isn't the vest-penetrating legend it's sometimes made out to be. It's a light, fast pistol cartridge with expanding and FMJ options.

The 5.7 loads worth knowing

Ammunition Depot's 5.7x28 section lists loads from FN, Fiocchi, Speer and Hornady. Defensive-minded buyers usually narrow it to these:

For range use, Fiocchi and FN both offer FMJ loads in the same section. On the 9mm side, the 9mm ammunition section has range and defensive loads from every major maker.

Barrel length matters more for the 5.7

Bottlenecked rifle-style cartridges tend to be sensitive to barrel length, and FN's own figures for the 5.7 show it. The same V-Max load runs noticeably faster from the P90's longer barrel than from the Five-seveN pistol, and the SS195LF hollow point drops by about 90 meters per second going from the P90 to the pistol, according to the cartridge's reference entry.

That has two consequences. First, if you're reading velocity numbers online, check which gun they came from. A carbine figure will flatter a pistol. Second, the 5.7's defensive bullets are light, and light bullets lean heavily on velocity to perform. A shorter barrel takes away some of what makes the cartridge interesting.

9mm is more forgiving here. Its straight case burns its powder fast, and while short barrels still cost velocity, makers build entire product lines around short-barrel 9mm pistols. Our 9mm bullet weight guide explains why heavier 9mm bullets are popular in short guns.

The platform question

Picking a cartridge also means picking a family of guns, magazines, holsters and spare parts.

• 5.7 pistols are typically full-size, with long grips to fit the long cartridge. Good for the range, the nightstand or open carry; harder to conceal than a compact 9mm. Holster choice is improving but still narrower.
• 9mm pistols come in every size, from micro-compacts to long-slide competition guns, and the holster, light and optic ecosystem around them is enormous.
• Carbines exist in both. A 5.7 carbine like the PS90 gets the most out of the cartridge's velocity, while 9mm carbines have a large following of their own and run on the same ammo as your pistol.

If you already own several 9mm guns, a 5.7 adds a new ammo type to stock and track. That's not a deal-breaker, just a real cost in shelf space and attention.

Who should actually buy one

A 5.7 pistol makes the most sense as a second gun for someone who already owns a 9mm, wants something with very low recoil and high capacity, and enjoys the range. It can also suit a recoil-sensitive shooter who has tested one and shoots it well, as long as they accept the narrower ammo choice and higher cost.

It makes the least sense as a first and only handgun for someone on a budget, or for a carrier who wants the widest range of proven defensive loads and holster options.

Whatever you buy, store it locked and unloaded when it's not in use, and keep ammunition separate from children and unauthorized users.

The call

Editorial note: This is an independent editorial overview built from manufacturer specifications, retailer listings and published sources. We have not performed hands-on testing of the products discussed, and nothing here is a performance guarantee. Verify specifications, compatibility and the law where you live.

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