There were a lot of things I liked about the film, and some stuff that I as an ex-military guy have a hard time accepting:
-A soldier would never leave his helmet unbuckled, because it would fall off the first time he had to move quickly.
-Unless it was destroyed, he would never leave his rifle, and if it was, he'd take one off a dead enemy.
-The muzzle flashes take away from the action. If you're going for any sort of realism, they'll be basically invisible during the day, and if they are visible it will be for only one frame. Also, the M4 doesn't make a star-shaped flash. There are a lot of good tutorials by guys like Film Riot and Freddie Wong for good action flick muzzle flashes.
-The weapons fire sound effects were pretty good, but inconsistent with the type of rifles being used. Watch some videos of guys shooting that stuff on the firing range to hear what they sound like. The M4 has a very distinct sound to it that is unmistakable to anyone who has heard it. Your AK47 sounds were fine. Also, put some reverb on those interior shots, maybe a small or medium room preset. It helps sell the idea that you're shooting a weapon in a concrete building.
-When the soldier tosses the brick and sneaks up on the enemy with his pistol, the enemy gives up. If that were real life, the enemy would do absolutely anything to stay alive, probably try to spin around and grab the gun.
-The bad guy who tackles the soldier... why not shoot him in the head after he has passed, or at least use a knife one him? I know you want that cqc action, but maybe have a good reason the enemy has lost all of his weapons.
That's all for critiques... on to the good stuff! I thought the color grading was excellent, and the exposure was pretty consistent throughout. A couple of blown out highlights here and there, but nothing to worry about. Also, the score was great. Very fitting for the scene. Good usage of costumes, although they were wayyy too clean for a bunch of soldiers in a bombed out building exchanging gunfire and grenade explosions. Have your guys roll around in the dirt, make them sweat or spray their faces with spray bottles to simulate sweat. Overall though, great stuff!
I hope you take my suggestions as constructive criticisms. I'm just an amateur like you.