The robbers use a shaped charge to breach the doors of the armored car. While this would have worked, it also would have instantly killed the guard in the rear of the vehicle and probably severely injured or killed the driver and the guard riding shotgun.
A shaped charge focuses its blast inward to create a special type of hole or explosive effect. That means not only would the explosion have been focused to the INSIDE of the armored car, superheated plasma and chunks of metal created by the blast would have done so as well. Killing the guards due to Waingro's incompetence wouldn't have been unnecessary as they likely would already be deceased.
SUPER MAJOR PLOT HOLE (SPOILER)
The robbers net $12 million, per Kelso's estimate. That means that each one would have been carrying between 80-100 pounds worth of currency in duffel bags when they exited the bank. The film next scenes make this highly improbable.
They are shown engaging in a 10 minute running gun battle with LAPD with the bags hanging from their backs. Not only do they defeat a larger number of police officers while doing, they are able to do so far too easily for people carrying such a large amount of weight on their person while doing as such.
Minor Plot Hole/Unaddressed Issue
Considering that they didn't seem to expect too much opposition when robbing the bank, the group came to the job extremely well-armed. When watching the film, it's clear that they expend roughly 150-200 rounds apiece at the police when they are forced to make their escape on foot after the death of their getaway driver.
This seems incongruous as that much ammunition would have required multiple clips (meaning more weight) and shooting it out with the police would have meant that additional prison time would have been in store for them if they were caught.
Minor Plot Hole (SPOILER)
For a criminal who the film portrays as being highly intelligent, Neil McCauley makes some exceptionally amateurish mistakes. These include:
1) Reading a book about metals in public ( for one of his jobs) and then being surprised when a store employee recognizes him at a diner with that book.
2) He attempts to kill Waingro for his incompetence in the parking lot of a crowded diner with a firearm and then allows him to escape.
3) Engaging Roger Van Zandt's men at the drive-in theater where he's expecting his payoff instead waiting to determine if was indeed a setup. If he had, he simply could have avoided trading gunfire with them and taken Van Zandt "out" at a later time.
4) When it's clear that the "heat" is on him, he continues with the bank robbery. While Shiherlis (Val Kilmer) needs the money, the remainder of the group doesn't and doing the job with so much police surveillance will likely get them all arrested.
5) When Trejo pulls out of the job because he is being followed (which turns out to be a lie) McCauley still continues with the job using as a driver an ex-con he knows from prison. While the ex-con does his job, it's obvious that robbery has been compromised.
6) McCauley wastes valuable time getting out of LA after the robbery going to see Trejo (he allegedly was worried about Trejo having given the police the group's escape plans) and then traveling to kill both Van Zandt (the currency trader who tried to have him killed) as well as Waingro, who he finds is at a hotel near the airport.
It's clear that Neil McCauley is the "weakest link" in the group which he leads.
The police have nothing to hold Chris Shiherlis' wife on. She isn't apparently wanted for any crimes and if she had simply asked for an attorney, it's doubtful that they could have even arrested her. Being the wife of a criminal is not in and of itself a crime; nor does the film show her committing any criminals acts herself.
Using her as "bait" to catch her husband, especially with their baby in the house, would have been a non-starter all the way around.
Bank robbery is a federal offense in the United States. Yet at no point during the film does Vincent (Al Pacino) even suggest (as he should have) that the FBI become involved in the matter.
Unaddressed Issue (SPOILER)
Vincent, the protagonist, played by Al Pacino is a a great deal of trouble in the wake of the film. By refusing to arrest Neil MacCauley and his crew for what would have been serious felonies and trying to get one to flip on the others, he instead allowed them to remain free and commit a bank robbery where multiple LAPD officers (and some were probably killed) and he allowed MacCauley to escape which lead to the deaths of three more people (Trejo, Van Zant and Waingro).
While the film ends on what is supposed t= be the "positive note" of Vincent getting his man, he would likely face forced retirement if not lose his rank or his job after the fiasco of that day.
How did Waingro know about the bank job, in order for him to rat to Hugh Benny and Roger Van Zant, so they in-turn could rat to the Pacino's crew? Waingro was involved in ONE of their robberies, at the beginning of the film. ONE! Who else knew about the bank job that could spill it to Waingro? No one. Yes, it was inconvenient that Neal's crew was ratted on as they were robbing the bank, but how did Waingro get the info to be able to rat it in the first place.
How did Natalie Portman’s character knew the hotel Vincent was staying at? On the previous scene when he kicks the ya set out of the car you can see the suitcase on the front seat so that means this is the first time he was heading there is this mentioned before in the film?
I wonder about the ER scene. Did De Niro open the door with his elbow because of A) convenience B) germs C) fingerprints D) something else? If it's convenience or he's a germaphobe, then whatever. But if fingerprints is the answer, which I think the camera zoom-in implies, it wouldn't make much sense. He's walking all the way through a large hospital with cameras and unexpected locked doors. Who cares about a button that's going to get touched by 40 more people in the next couple days when the camera footage is going to show everything? Why not just walk up and hop in the ambulance?