Close combat is dangerous as fuck, always. The most dangerous shit is entering and clearing a house, and then realizing it's been fucking booby-trapped and you have absolutely no fucking idea how much explosive material is in there. It could be an anti-personnel mine's worth. It could be enough to level the whole structure.
In the Middle East, a lot of houses are made of stone or mud brick and are extremely resistant to rifle fire. In Eastern Europe, there are a lot of brick and concrete buildings. Those buildings are basically bunkers. If someone is firing from one, it will take many rifle hits in the same place to chew through.
Nobody ever just rushes in and assaults a fortified location on foot. That's how people die. Imagine someone is firing a PKM from a window, and the whole wall of the structure is stone and you can't hit him with an overpenetrating hit at all, and no part of him is exposed long enough to even see the guy.
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Would you just run at that guy across an open field with your rifle in hand like you're gonna go inside there and kill him? No. He lines up on you, puts a burst in you, and now you're dead.
That's why you wait in a ditch 400 meters away for the big boom.