World's first AR FiveSeven Carbine? Possibly

The gun shop where I work may well have created the world's first AR Five-Seven Carbine. What's that, you may ask?

The FN Herstal Five-Seven Pistol (top right) and the FN PS-90 Personal Defense Weapon (top left) share a new cartridge developed by FN, the 5.7x28mm, basically a short version of the .223/5.56x45mm NATO. If you convert the 5.7mm into its equivalent in inches it comes out to about .224 caliber, so it's just 1/1000th larger in diameter than .223. But the latter number indicates the length of the two cartridges, 45mm for NATO and 28mm for the FN 5.7mm.

But now the differences between the two have been bridged by a company that creates the AR Five-Seven upper assembly, designed to fit on the lower assembly of most AR-type rifles and carbines. Which is exactly what we did at our shop as seen in the third photo.

We took an AR Five-Seven upper assembly, which fires the 5.7x28mm round, and installed it on a Rock River AR lower assembly and voila! The world's first AR Five-Seven Carbine. Maybe. At least it's the first one I've ever seen or heard about. But since the AR Five-Seven upper assembly is on the market, surely some enterprising gun shop has put it on an AR lower assembly and is selling the duo as a complete AR Five-Seven carbine or rifle. Maybe so, but this is know for sure. Our shop has one and I listed it today on gunbroker, so you can have one.

Or you can buy yourself an AR Five-Seven upper and put it on your AR. Or you can buy both the AR Five-Seven upper and the Rock River lower assembly and build your own. But if you do, don't forget you gotta have the FN Five-Seven PDW magazine to make the thing work. And you gotta have some 5.7x28mm ammo too. If you can't find those, give the shop a call. We've got 'em.