Ok, I'm going to preface this post by saying if I'm wrong about it, I'm wrong.
However, having spent some time over there myself, I have a few observations.
I believe this video to be a FAKE.
My reasons are as follows.
1. Sound. Yes, the rifle/machine gun fire sounds authentic, however you do not ONCE hear any communication from other people in this guys unit. He yelled out dozens of times, and wasn't answered once. Having been in his situation on a few occasions, I can attest to the fact that there is so much verbal exchange that it can become a problem processing everything everyone else is saying all at once. Yet in this video, you hear nothing but silence in that department. Just this guy yelling out stupidly. Also, I've heard the reaction from when people are shot. They don't yell out in any way shape or form in the manner this idiot does. It just sounds too fake. In the last sequence going "uhhh" to yelling out "I'm hiiiiit" in the same virtual instant...sorry doesn't happen like that. I mean just listen to it and try not to laugh at this guy faking it.
2. This persons lack of skills. His magazine change and empty mag management were a joke at best, and no trained soldier I've ever seen would fumble about this badly. Also, something about the way he struck the magazine release to send his bolt forward just struck me as amateurish like an untrained range shooter or something like that as well. Also, as you can see when he dropped his weapon several times that he didn't have it secured to his body when there was a nice double loop sling just sitting right there. Nobody I've ever seen or worked with would leave cover to begin an ascent or descent without first ensuring his kit, primarily his WEAPON was attached to him first. Also, he set his weapon DOWN ON THE GROUND while performing a reload. This in of itself is beyond laughable. There are several other things which just scream amateur. Also, when using a hand to assist you in moving through obstacles or terrain, you NEVER use your primary weapon hand, you use your SUPPORT hand. That's why it's called a SUPPORT hand. This guy just does so many things wrong I can't begin to point them all out.
Also, his emergency reload as I said is a complete joke. He makes two distinct movements inserting his magazine, then "slappin er home" just like you see guys do at the aforementioned ol' shootin range is precisely how NOT to do a rapid magazine change. When you are under fire you show just a tad more intensity when executing these things than this moron does. Rolling his rifle to observe the chamber during a non-malfunction drill was also a complete waste of time and very VERY lacking in the economy of motion that most well trained persons will execute during a tactical or emergency reload.
3. Equipment in Video. The rifle this guy is using is just too.....clean Also, it is nearly black in color still. Ask Junky or Iraqvet, or anyone else who has been in the desert theaters, and they'll agree that NO rifle has ever been so "black" and clean before or since this video. Also, his "Oakley gloves" may look cool in video games and the like, but they are far too clean and white still to belong to any operator I've ever seen. Also, where is the AN/Paq 4 laser designator? Something that isn't very common on the ol' range M4, but an item that is attached to virtually every M4 you can find in the 4th Infantry Divisions pictures from Afghanistan.
4. Dust hits from incoming fire. These are way WAY to small to represent strikes from 7.62x39 or 7.62x54 fire, the typical Taliban ammunition. They in fact are strikes from a paintball gun shooting dust balls or something similar, I'll bet my fortune on it. Look at them again in the video yourselves, and take out your trusty rifle and shoot it into some dust like in this terrain, and you'll get the idea. Also, when the rounds supposedly come in and "strike and destroy his m203", it looks more like he half bellybutton flips/tosses his rifle away when he drops it, as opposed to having it blown out of hands. Watch it a few times and look really close at the rifle when the sound of the rounds striking is added in.
In closing, what we are seeing here I believe is a guy in a rock quarry in the good ol US of A and his buddy filming a few shots going out with another guy behind the camera shooting some dust balls into the ground, and then a sound edit on PC desktop software adding in some realistic battle sounds taken from other videos.