Speaking of instruction of the actors....
First, Michael Mann is a shooter. He's attended several of the shooting schools, including Gunsite.
Secondly, Mann contracted with the Los Angeles Sheriff's Dept., to use one of their ranges at the sprawling Weapons Training Facility at Pitchess Detention Center, in Saugus, north L.A. County, for the training sessions.
The SAS guy was the overall trainer, but several LASD Weapons Training Instructors of the Advanced Training Bureau, were used to train the actors, especially in the standard "police technique" of handgun, shotgun, rifle, and submachine gun shooting, so the "cops" would look authentic.
All practice and firing was under the constant supervison of LASD Instructors.
Sidlelight: Al Pacino hates, loathes and despises firearms. As soon as he'd finish firing a gun, he'd literally throw it down on the mattress beside him, as if it were something obscene in his hands. His attitude, especially to the "blue collar laborors," was very typical of your usual mega millionaire liberal.
DeNiro, although very standoffish and reserved, soon took to the instruction, and learned as much as possible in the time they were there, although there had to be an "attitude adjustment" with him and his manager, before the actual firing began.
Val Kilmer? Kilmer was a shooter, par excellance! Friendly, outgoing, extremely interested in learning all he could, and made friends with the LASD instructors. He's a shooter, too.
Triva: DeNiro got "conned" by one of the inmate trustees, who worked the range. (P.D.C. is a very large prison, containing, usually, up to 18,000 prisoners. Some of the prisoners become trustees, and they work, among other things, the ranges, pulling and pasting targets, mowing the lawns, and myriad duties.) One of them, totally against orders, got next to DeNiro, conned him ("I just wanna go straight, Bobby..."), and even got DeNiro's home phone number!!
Anyway, that's how the actors were trained in "realistic shooting." FWIW. J.B.