The MDR has been out in the market for five years now, and DesertTech has been making some improvements. The current production model I called the MDRX, to denote several incremental improvements that have been made to the system. The gas block now has drainage holes, the polymer blend has been strengthened, and the trigger geometry improved, among other things. In addition, they now have the Micron configuration available. This is an SBR pattern in 5.56mm, which shares the same receiver and lower as the standard MDRX - it's just a barrel and handguard swap.

The Micron has an 11.5" barrel, which is basically as short as can be fitted tot he standard MDRX receiver. The whole rifle is just 23.5" overall, although it still weighs about 7lb 5oz - it's a dense little thing. It is only available in 5.56mm, and only (for now) in the side-eject configuration.

I found it to be a very comfortable carbine to use, and surprisingly accurate for its size.