When Nolan and Bishop capture the thief in the game room, Nolan takes the thief's backpack off, yet when they leave, neither Nolan or Bishop are carrying it.
When Nolan shoots the suspect in the upstairs bedroom, a gold inner barrel can be seen in his handgun. This shows that his service weapon is actually an airsoft replica.
When Nolan fires on the suspect inside the house, the barrel of Nolan's gun is clearly visible, revealed to be indeed an Airsoft gun, powered by propane to simulate the cycling of a real firearm. More than likely this was used to eliminate the sound possibly damaging the hearing of the actors inside an enclosed space, as well as eliminate the dangers of a blank round being fired in such close proximity to another person.
In an operation such as the drug buy, the police would not just cover the front of the building. They would cover all exits so that the suspects could not escape as took place.