I first started inquiring about 5.45 AR's a long while ago, way before the election. Few people had run one so I decided to hoard ammo in the meantime. Now it's back to where I have the $$$ to fork out for an upper again so I figured run the question again to see if there's more out there now to go around. How's the S&W 5.45 upper working for you guys who've tried them?