Ruger has a carbine that fires the 5.7 round, the Ruger LC and The Firearm Arm Blog give their take on this below US$1,000 5.7mm rifle after some use... "In this episode of TFBTV, @JamesReeves performs an extended review of the Ruger LC Carbine. The Ruger LC Carbine is a light and compact, not to mention inexpensive 5.7x28mm carbine that has a number of well thought out features including a cold hammer-forged barrel with a threaded muzzle for easy attachment of muzzle devices. It includes a folding 6-position adjustable stock that is compatible with AR type buttstocks and removable for use of picatinny rail compatible stocks. Other features of the Ruger LC Carbine include a reversible magazine release, full length optic rail, ambi controls, and more. But James did run into a problem with the carbine on the range. Watch the video to see the verdict."