Nice stuff ^^ The gun has a great feel, the Hud on the gun is a very good idea and it's really fun to shoot enemys ^^
I have a few issues though:
The player can get through the floor if it tries to go under the ramp.
It's unclear when an ennemy see you. I think a sound would fix that.
The turret line of sight isn't clearly defined. i would add a visual line from the turret to the player.
The hand grenade isn't really usefull. I just shot stuff from afar.
Overall I had fun ^^ Keep up the good work ^^