An example of combat ineffective rates in real combat

[Imp]

Training
Dedication to their cause
Knowledge of what your opponent will do to you if you lose
Loyalty to your squad mates

Forgot about point 3 & point 4 has more merit than you might think.

On ammo use comes down to training & doctrine I suppose.
Covering or suppressive fire is doctrine if its done on purpose.
Simplifying it theres probably 2 mayor types of troops.
Those that pop their head up take a quickly aimed or pot luck shot & duck down behind cover before they get shot.
&
The ones that stay on post waiting for the guy they have seen doing the above to put his head up again in the same place.