This is because its not a reliable gun. It started melting when fired repeatedly. X stood for experimental.

They upgraded it though. The biggest problems were the handgaurd melted and the battery didn't last for the integral sights. They, to get re-evaluated made the handguard out of a more reliable material and extended battery. Also when tested to be a possible replacement for the M16/M4, it showed less stoppages than the M16 and several other contenders. In short, it had its shortcomings but still is a reliable.

well, for whatever reason. it wasnt deemed reliable enough by the dod

It actually was but just phased out for reasons unknown.

haha. Yeah im sure that was what the official statement was.