Light pdw for ambi-shooters - AR57 ULT 12in Barrel 5.7x28mm Upper Receiver Assembly

I purchased this out of curiosity. Ammo prices have come down to $.40/round. Hopefully, they will drop to a more reasonable $.20/round based on their actual cost to manufacture. The upper had a very stiff action at first. I disassembled it, cleaned it up and regressed/lubed it. After repeated cycling, dry firing, and actual range trips, it is operating a lot smoother. Still not as smooth as an AR-15 action though. I paired this with a polymer lower and 3 lbs trigger with no uptake. This makes for a super light and fast shooting gun. Having 50 rounds onboard makes it a great truck gun option that can reach out and touch things at 150m. I've had one malfunction that was probably the ammo. I was firing Fiocchi rounds and it pushed the nose of the round back into the case during loading. I had to pull the magazine to extract the round. Other than that, this thing is a flat shooting beast that can pepper targets in the A zone at distance.