5.7x28 vs 9mm

So, you were about to grab another boring old 9mm pistol when you stumbled upon a 5.7x28mm pistol. While it is nowhere near as common as the 9mm cartridge, the 5.7x28mm cartridge has some very different, very enticing performance features. In this article, we will go over these differences to help make your decision about which pistol to buy a little easier.

Physical Attributes

When viewed side by side, it would be difficult to point out a single similarity between the 9mm and the 5.7. In fact, the only similarity they share physically (other than materials) is the use of small pistol primers (though some 5.7 loads use small rifle primers). Past this common primer type, these cartridges could not be more different.

Perhaps the first difference you will notice is the shape of these cartridges. The 9mm features a slightly tapered case, and the 5.7 utilizes a bottleneck design that mimics a miniature rifle cartridge. While both case types are extremely reliable (assuming you’re using high-quality firearms and ammo), the bottleneck design of the 5.7 gives the cartridge a much larger case capacity than would be possible with another case type.

Looking at the business end of each cartridge, you will notice a very large difference in the projectile diameter of each. Just like a 223 Remington or 5.56 NATO, the 5.7x28mm utilizes bullets that are 0.224 inches in diameter. Using much larger 0.355-inch diameter projectiles, the 9mm boasts a 58.5% increase in diameter over the 5.7.

This increase in diameter allows the 9mm to be loaded with a much wider and heavier range of bullet weights. In fact, the 9mm can be found loaded with bullets weighing up to 165 grains (though this is somewhat uncommon). By comparison, standard 5.7x28mm ammunition is most often loaded with 40-grain projectiles, with some subsonic offerings ranging up to 62 grains. 

Power

If you’re entertaining the thought of these small cartridges, chances are, you aren’t very concerned with the amount of power they produce. While power may not be a top priority, you’ll probably be shocked to learn that these cartridges produce similar muzzle energy figures despite what their dimensions would have you believe.

Looking at Speer’s 115-grain Gold Dot offering in 9mm (standard pressure load), we see that it produces 355 ft/lbs. at a muzzle velocity of 1,200 feet per second. The Speer 40-grain Gold Dot in 5.7x28mm produces a respectable 288 ft/lbs. at a muzzle velocity of 1,800 feet per second.

So, although the 9mm produces about 23% more muzzle energy in this example, the 5.7 is going 50% faster out of a handgun. Increased velocity not only means that the 5.7 will get to the target faster, but it will also be substantially flatter shooting.

When we move to longer barrel lengths than traditional handguns encompass (> 6 inches), we start to notice a greater increase in velocity with the 5.7 over the 9mm. This is primarily due to the much higher operating pressure of the 5.7 (48,500-psi max according to new SAAMI specs) compared to the operating pressure of a standard 9mm (35,000-psi max according to SAAMI).

As velocity increases, so does muzzle energy. This means that the 5.7 surpasses the muzzle energy of many 9mm loads and does so with a much flatter trajectory. So, if you were considering a rifle-length barrel (16” +) or similar setup chambered in either cartridge, the 5.7 becomes a far more enticing option.

Recoil

If you’re looking to shoot as quickly as possible, recoil should be a primary concern. Although these cartridges may produce similar muzzle energy figures, the 9mm is often loaded with bullets weighing more than three times the 5.7 bullets. This translates to significantly more momentum both down range and at the shooter’s wrists.

With the 115-grain load referenced above, the 9mm produces approximately 5.7 ft/lbs. of recoil from a 25-ounce handgun (approximate weight of a Glock 17 with an empty mag). While this figure may not be significant compared to most other handgun cartridges, it is nearly three times the 2.1 ft/lbs. of recoil generated by the 5.7 from a handgun of the same weight.

In the field, this increase in recoil makes a noticeable difference in keeping each cartridge on target, though the 9mm is still very controllable. It should be noted, however, that effective muzzle brakes and similar devices can reduce 9mm recoil levels to feel like the 5.7x28mm.

Cost

Let’s face it: The 9mm is the most popular centerfire handgun cartridge on the market. With its massive popularity comes extremely large production volumes, which help make it the most cost-effective cartridge available. This affordability often leads to longer sessions at the range, ideal for those looking to train.

Although the 5.7x28mm is a popular cartridge and seems to be getting more popular by the day, it does not compete with the 9mm’s massive fan base. Decreased popularity not only means significantly fewer factory load options offered in 5.7, but it also means significantly higher prices. In fact, factory-loaded 5.7 offerings are typically double the price of comparable 9mm FMJ loadings, if not slightly higher.

These prices cause many to shy away from the cartridge, though we must realize that the 5.7x28mm continues growing in popularity. In recent years, a growing list of budget-oriented firearm options has spiked interest in the cartridge, ultimately leading to more ammo options. With these options have come somewhat lower prices, though this does not mean that prices will ever reflect the 9mm.

Suppressibility

With the massive popularity of suppressors, there’s a good chance you’re looking to suppress either of these cartridges. If your goal is to shoot as quietly as possible in as compact of a platform as possible, few cartridges do it better than the 9mm. With relatively heavy bullet weights, subsonic 9mm ammo not only produces great muzzle energy figures (relative to supersonic), but it also functions reliably in nearly every setup.

While several subsonic offerings are being introduced for the 5.7, bullet weights seldom exceed 62 grains. When fired at subsonic velocities, these lightweight 5.7 offerings barely surpass 150 ft/lbs. of muzzle energy. In addition to these shortcomings in muzzle energy, potential reliability issues also arise due to the lower operating pressures generated by these subsonic 5.7 offerings.

Which One Should I Choose?

In nearly every metric, the 9mm and the 5.7x28mm are very different cartridges that offer very different performance. With all these differences, you’re probably wondering which is the better choice.

If you’re looking for a high-velocity semi-auto handgun cartridge capable of flat trajectories, few do it better than the 5.7x28mm. Out of rifle-length barrels, the 5.7 really begins to shine above the 9mm, though its performance is dwarfed by any intermediate rifle cartridges. You must realize, however, that the 5.7 is not ideal for subsonic fire, and range days will be far more expensive than with 9mm.

While the 5.7 may experience reliability issues with subsonic offerings, the same cannot be said for nearly any subsonic or supersonic 9mm offering. With its massive popularity, decent muzzle energy figures, and low ammo costs, it would be difficult not to have a 9mm in your collection.

Regardless of their differences, know that you’re making a great choice with whichever cartridge you choose.

--Banana Ballistics