I put this one together over the last several months, pretty much along the same timeline as "Scrapy", except that every part was bought new. The purpose of this build was to add a light-weight, controllabe, carbine to the safe, that can accept a small Red-dot in the future and other upgrades (forearm, buffer, etc). It is also ideal for a second upper to carry in a backpack that can complement the SPR that I have in the works. Upper receiver is an Aero Precision, which I had heard positive feedback about and I wanted to deviate a bit from "the usual". The lower is a Surplus Arms and Ammo, which I've had nothing but success lately. Fit and finish on both are perfect. Barrel is a Green mountain M4 barrel, 5.56 1:8 , with Chrome lined chamber and bore, composed of 41V50 vanadium alloy milspec steel. I was very pleasantly suprised by the quality and ease of fitting a gas block. Minimal fitting was required to get the bottom rail where I wanted it on HG. The feel is great and I was able to test fire it in town! My home gun store (I'm finally claiming them. . . ) now has a testing tube that I can use freely! The gun functioned flawlessly! Recoil was very acceptable with an H buffer installed. Very hapy with this one!