Things I liked:It took some maintenance on my part with the magazine to get it to hold gas but once I got the magazine functioning properly the rifle performed just as I had hoped. The gun has the strongest recoil I've experienced on any gas blowback rifle that I've owned. Of course it is the only gas blowback M4A1 rifle that I've owned that actually functioned as it should. For that I am extremely happy. The rifle has an okay rate of fire but not impressive. I would have preferred it that the rifle had semi-automatic and three round burst, instead of full auto. The build quality on the rifle is very solid with absolutely no loose parts. Everything is tight and the rifle has some nice heft to it especially with the magazine inserted. I love that KWA included a speed loader with the rifle. Makes loading the magazine a breeze. Things I would have changed:As I mentioned before, the rifle might perform better with a three round burst setting. On full auto the rate of fire is not that impressive and seems to slow down if the trigger is held down for longer than five seconds. Might have something to do with the size and weight of the bolt carrier. The rifle functions much better on semi-automatic. I don't know if it was just my rifle or if all of them are this way, but I was under the impression the rifle use an all metal construction but I discovered that the carry handle is actually plastic. It is not really a big issue with me especially since you can easily replace the carry handle with a metal one but I thought I mention it. It would have been nice if KWA included a valve key with the rifle since the magazines seem to require maintenance to keep them functioning properly. Disassembly is easy enough with common household tools, with the exception of the valve key but reassembly can be frustrating and I wish KWA had designed a better way of resealing the gas reservoir. What others should know:Though the sight says to use with .20 gram bbs KWA recommends using at least .25 gram bbs. I use King Arms Bio bbs.