The centerfire FN 5.7x28mm service round is fired by a variety of sub-machine guns (for which the cartridge was originally developed) and the Five-seveN pistol manufactured by Fabrique Nationale de Herstal (FNH) of Belgium. In appearance, it looks like a miniature rifle cartridge. FN credits the 5.7x28 with an effective range of 55 yards when fired from their Five-seveN pistol. (Presumably, they mean against human targets.)

The 5.7x28 is based on a centerfire, rimless, bottleneck case with zero body taper and a sharp 35-degree shoulder. The case length is 1.135 inches and the cartridge overall length (COL) is 1.594 inches. FN 5.7x28 ammo is loaded to the unusually high maximum average pressure of 50,037 psi. This and the shape of the cartridge make it unsuitable for use in the great majority of existing semi-automatic pistols, whose actions were designed for lower pressure cartridges with conventional case profiles.

The 5.7x28 is not a mainstream civilian handgun cartridge, at least in the US, but it is slowly becoming better known. However, as this is written in the summer of 2014, both 5.7x28mm ammunition and pistols to shoot it remain scarce and expensive. It has found much wider acceptance among military users, usually in sub-machine guns. It is reportedly in service with some 40 military organizations around the world.

Since the 5.7x28 is a sub-machine gun cartridge, it is easy to confuse the ballistics derived from 10.35 inch sub-machine gun length barrels with the ballistics from a 4.8 inch Five-seveN pistol barrel. Being less than half the length, the pistol barrel achieves significantly less muzzle velocity (MV) than a sub-machine gun. Federal factory load ballistics for the 5.7x28mm claim a MV of 1655 fps for a 40 grain FMJ bullet from a 4.8 inch barrel.

Interestingly, this makes the 5.7x28mm inferior to the obsolete .22 Jet, a .22 centerfire revolver cartridge based on a necked-down .357 Magnum case designed by Remington for Smith & Wesson. When introduced in 1961, the .22 Jet claimed a muzzle velocity of 2460 fps with a 40 grain bullet. This proved to be optimistic, with the cartridge actually delivering about 2000 fps from a S&W revolver. S&W quit making .22 Jet revolvers due to the sharply tapered case setting back upon firing and jamming the cylinder.

Another cartridge to which the 5.7x28 has been compared is the .22 WMR, which brings us to the reason for this article. It seems strange to compare a very high pressure centerfire cartridge to a moderate pressure rimfire cartridge, but that is what we are doing.

The .22 WMR (Winchester Magnum Rimfire) has been around since 1959. It is a straight cased, rimfire cartridge. Its case length is 1.052 inches and the COL is 1.35 inches. The loaded cartridge is, therefore, about 1/4 inch shorter than a 5.7x28 cartridge. The MAP is 24,000 psi.

The .22 WMR is popular in both rifles and handguns, principally revolvers in the latter case. Based on a rimmed case that is long in relation to its diameter, it is not well adapted for use in autoloading pistols, although Kel-Tec offers their interesting PMR-30 autoloader, which was designed for the .22 WMR cartridge.

The .22 WMR offers more stopping power than the .22 Long Rifle and a flatter trajectory. It is an excellent field cartridge for shooting varmints and small game at moderate range (when chambered, for example, in the large Contender single shot pistol or a Ruger Single Six Hunter revolver) and for use in a kit gun.

Its trajectory is comparable to the other standard magnum revolver cartridges (.327 Magnum, .357 Magnum, .41 Magnum and .44 Magnum), which means it can be zeroed at 100 yards without shooting over normal size targets at intermediate distances and its ammo is far more compact. A 50 round box of .22 WMR ammo is not much larger than a 12 gauge shotgun shell and only a fraction of the size of a 50 round box of centerfire magnum ammo. I have, for example, often carried a .22 Magnum revolver as a sidearm on camping and fishing trips.

It is also offered in a number of handguns useful, or specifically intended, for personal protection. The selection includes the aforementioned PMR-30, derringers, mini revolvers, snubbies, compact (small frame) revolvers and full size (medium frame) revolvers. .22 WMR ammunition is available from every major US manufacturer of rimfire ammo, widely distributed and inexpensive.

Bullets

Both the 5.7x28 and .22 WMR shoot .224 inch diameter bullets. (The 5.7mm is mis-named, as it is actually a 5.56mm.) FN 5.7x28mm factory loads are available to civilian shooters with bullets weighing 28 grains (JHP) and 40 grains (V-Max polymer tipped and FMJ). .22 WMR factory loads from CCI, Federal, Hornady, Remington, Speer and Winchester are offered with bullets of all types (V-Max and other polymer tipped, JHP, JSP and FMJ) weighing 25, 28, 30, 33, 34, 40, 45, 50 and 52 grains.

Velocity

Among the major US ammunition companies, only Federal (in their American Eagle brand) offers a 5.7x28mm factory load. This uses a 40 grain FMJ bullet at a claimed MV of 1655 fps from a 4.8 inch pistol barrel.

When the .22 WMR cartridge was introduced, Winchester factory ballistics called for a handgun MV of 1550 fps with a 40 grain bullet from a 6 inch test barrel. Current factory handgun ballistics call for a 30 grain bullet at a muzzle velocity of 1610 fps and a 40 grain bullet at a MV of 1428 fps.

Energy

The muzzle energy (ME) of the 40 grain FMJ .22 WMR bullet is given as 181 ft. lbs. The catalog ME of the 40 grain FMJ 5.7x28 bullet 243 ft. lbs.

Not surprisingly, the 5.7x28 is the more powerful cartridge, with a 36% advantage in kinetic energy. However, the difference in energy seems less than one might expect from a cartridge operating at over twice (200%) the pressure.

Trajectory

Both calibers shoot flat enough to be zeroed at 100 yards, at which distance the 40 grain .22 WMR bullet would have a 50 yard rise of about 2.8 inches and the 40 grain 5.7x28 bullet a 50 yard rise of 1.8 inches. Thus, the 5.7x28 has about an inch less midrange rise than the .22 WMR over 100 yards. Of course, the lighter bullets at higher velocity shoot flatter in both calibers, particularly the 33 grain, plastic tipped spitzer bullets in .22 Magnum, which have a higher ballistic coefficient (lower drag) than the flat point 40 grain FMJ bullet compared here.

Summary and Conclusion

When you compare the ballistics of 40 grain bullets from both cartridges, the winner in every performance category is the 5.7x28mm. It could hardly be otherwise, since it uses a larger case with greater powder capacity and is loaded to over twice the MAP. Those who claim the .22 Magnum is equal to the 5.7x28 are simply wrong.

However, I do find it interesting the 5.7x28's margin of superiority is not greater. When its good performance, much lower cost and the vastly greater availability of both guns and ammo are taken into account, the .22 WMR seems like a viable choice.

.22 WMR ammo is available in a much wider variety of loads, bullet weights and styles, allowing the shooter to intelligently match the cartridge to its intended purpose and increasing its versatility. There are even special loads designed for use in mini revolvers with 1.5 inch barrels.

Clearly, when comparing these two cartridges there is much to consider. The 5.7x28mm is the winner in performance, while the .22 WMR simply makes more sense in other respects.