I've seen the video the FBI produced as a training tool, from what I've heard they got it right even though it was probably very painful for them. Got some very good info from it.
One of the FBI agents did move his shotgun to the backseat of his car before the fight. Car was not set up like a normal police car-no gun rack. This vehicle rammed the vehicle Platt and Matix were in and the gun slid into the floor behind the front seat, very hard to reach.
Another point was that Platt and Matix fired thousands of rounds and were very familiar with their firearms. As I recall only one agent did much shooting outside of training and quals.
Another point is that a Smith revolver (loaded with .38 +P's as I recall) fired the final fatal shots, and did a damned fine job of doing it. This isn't about one caliber of handgun not getting the job done, it's about going after a 3ft rattler with a 2ft stick.
Final points came from the interviews of the agents involved. To a man they urged those watching to carry more ammo. At the time bulges in one's jacket caused by a single speedloader, let alone two, were considered unsightly by many FBI agents. Many carried loop loaders, speed strips or simply a box of extra ammo in the trunk of the car or a briefcase.
No disrespect to the agents involved but they really didn't plan on getting into a prolonged gunbattle with determined, skilled, better-armed opponents that day. I'm sure they realized it was a possibility but they simply were not properly prepared or trained for what happened. Thank goodness the FBI learned from their mistakes and took steps to insure that it didn't happen again.