CQB - Shooting Through Walls
Undoubtedly an extremely controversial topic, we used to work it routinely. It involves the concept of shooting an adversary directly through an interior wall.
As I recall, and this is back I think early 1990s...a SWAT guy was shot by a bad guy through the wall, which brought up the discusion. In police, and sadly I suspect in your world as well, a great deal of learning takes place once something bad happens.
In any case...it was as if nobody had ever thought of that back then so of course, the experimentation was on.
The hard part is that urban dwellings may as well be made of paper for all the protection they offer. In fact, if one was to look at it that way it would lead to clearer thinking with tactics. Some guys use that as an indictment of the "stack" tactic, but that is wrong in my opinion. the constraints of the interior environment do place certain limits on how one can move, and specially on how a team can move.
Problem = How to keep a team dispersed but at the same time set the stage for a quick multiple man entry through a door?
Answer = There is no good answer and everything will be a compromise. The best solution is to do it fast, hard, and with as much surprise as possible so by the time the bad guy thinks of it, he is already dead. Not always easy to do. But back to shooting through the wall.
For example, your partner is moving into a room and takes fire at the door from the extreme left side of the room. You bring up your rifle or pistol and shoot from the area adjacent toe door to the extreme left area of the apparent room at face/upper chest level, then lowering your muzzle to where a man may go if he takes a knee, bring your shots back toward the starting point.
Think of writing a long "C" with your shots.
What is needed -
1). Certainty that the adversary is in the room alone. The only thing worse than missing a shot on a bad guy is shooting a non-combatant.
2). The ability to penetrate the interior wall. This is easily done with anything anyone would care to carry on a sling or in a holster. Note - Furniture may affect performance.
3). An understanding of human nature. When shots are fired, most people will drop their profile.
One thing to add. This is an ammo heavy exercise and a mere 5 shots or even 7 shots will be quickly insufficient. This was were we learned to stage the pistol magazine, as well where a 20 round or 33 round pistol magazine is useful, and where a 30 round stick in a long gun is even better.