The 5.7x28 FN

This diminutive Belgian import delivers smallbore steam from a very small package.

Article By Bob Forker

The 5.7x28 was developed by FN in the 1990s, and there is some pretty good evidence that it was originally developed for some real or proposed military application. At one time (perhaps still) there were four loadings with bullet weights ranging from 28 grains to 55 grains that included a tracer and a subsonic loading.

These loadings aren't available for civilian retail sale. They do suggest that FN has certainly considered other uses, other than just a simple pistol cartridge. And indeed, it was originally developed for the P90 Personal Defense Weapon.

Don't let the "5.7" part of the name fool you. This isn't a .23 caliber. This cartridge uses standard .224-inch-diameter bullets, the same as almost all .22 centerfires. As the picture shows, the 5.7x28 is what could be called a rimless Hornet--actually, it looks more like a rimless K-Hornet. If I could accurately predict which new cartridges would sell and which wouldn't, I'd be rich. Still, I think the 5.7x28 has good potential as a modern light .22. I would also suspect that by the time you read this somebody will have necked this neat little number to both .17 and .20 calibers. (I've done enough of that sort of thing and will leave this one for someone else).


The 5.7 x 28 FN

The only factory handgun being offered in this caliber is FN's Semi-Auto Pistol. It's interesting that while the factory is only producing 27- and 40-grain loads for civilian sale, the barrel twist in the pistol is a very tight 1:91?2 inches. That's enough to stabilize bullets up to about 70 grains and further suggests that the factory is still thinking about other applications down the road.

Bo Clerke made us two barrels, one five inches long and one 22 inches. At this writing, no one is building production rifle barrels in this caliber, but that will probably change overnight. It would sure make a great single-shot pistol. I know several companies are just waiting for a little demand to develop before cranking up their own production.

Today's ammo situation is interesting. FN is building some ammo with 27-grain aluminum-core bullets in Belgium, and Fiocchi is making some with 40-grain Hornady V-Maxs in Missouri but only to be sold through FN. So that's the only source of cases for the present. (Contact FN at 703/288-1292 for information.) Both the FN- and Fiocchi-built ammo styles employ staked-in primers in the military tradition. They both use Boxer primers and are easy to deprime but require reaming the residue of the staking off the mouth of the primer pocket before they can be reloaded. That's a bit of a drag, but you only have to do it once.

There are plenty of bullets that can be used and plenty of suitable powders. Our dies came from RCBS, but other manufactures have told me that can and will produce this caliber when the demand is there.

Because the present gun is a pistol, we used small pistol primers in our first development loads. It was easy to duplicate the performance of factory ammo, but at factory pressures our primers were a bit flat (see photo). We switched to small rifle primers. With identical loadings, the pressures and velocities we measured were identical with either style primer and the flattening went away with the rifle-style primers (of all brands). The gun had no problems firing the rifle primers either. I see no reason to use pistol primers in this cartridge.

The Hornet is only about 80 years old, more like 120 years if you include the .22 WCF, the origin of the Hornet. As is true of all old cartridges, the Hornet's pressures are very modest. The pressures we measured in 5.7x28 factory ammo were quite a bit more potent than Hornet pressures. That is to be expected in a modern cartridge that doesn't have any old guns to consider. Because it comes out of Europe, the pressure specifications for the 5.7x28 are controlled by a European agency called CIP (and not SAAMI) and therefore don't translate directly to the numbers we expect to see. It is no surprise that this slightly smaller-volume cartridge needs a little more pressure to match Hornet performance. There's no such thing as a free lunch.

Except for initially reaming the staking off the primer pocket entrance, reloading is straightforward. Since this cartridge holds only about 10 or 11 grains of water volume, you want to make any changes as you build up from the starting loads in very small increments. It doesn't take a lot more powder to go from starting loads to proof pressures.

We fired bullets from 35 to 80 grains in our testing. The 80-grain bullets were unstable from both the pistol- and rifle-length pressure barrels, so they aren't included in these loads. Obviously, this little number is at its best with the lighter bullets, but there could be specialized applications for some of the heavy weights. FN's subsonic and tracer loadings suggest that they may be thinking of some.

It is going to be interesting to see what happens to this caliber. It will make a very nice 150- to 200-yard small-varmint number. It can, and does, produce fine accuracy, the kind that's actually needed for varmint work. That's not a big surprise. I'm convinced that with good bullets and a good barrel, nearly any cartridge shape can be accurate. There's certainly no shortage of excellent .224 bullets.

Like the Hornet, the 5.7x28 will make a wonderful introductory caliber to get potentially recoil-sensitive shooters started on centerfire shooting.

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