Possum, there are two pieces of information that might be important to this discussion.
1. Can we see the security cams at all? I would imagine there would be cameras that relay to the control room. You have already said this back hallway is clear, but did we see any in the other areas yet in the hallway leading to the gun turret?
2. Is there actually windows for the two troopers to look out of for the E-Web cannon, or are they using computer screens for visual? Bottom line, can the two troopers outside the facility actually see into the gun turret to see if it is manned or not?
Given that we are not supposed to know the layout of the interior, it is kind of hard to determine where I would have gone first in opening the doors. But moving clockwise would appear to be logical. Mack will switch to single shot, but I am not a big fan of hand-to-hand unless we have to.