Modified [Benelli M Series Super 90 Shotguns#Benelli M2|[Benelli M2 Super 90]] Shotgun with pistol grip stock, extended magazine tube, rifle sights; modified for the movie to use box or drum magazines, used by the "Slag" robbers at the beginning of the movie.
I don't know who changed this, but its and M2, not an M1. Note the shape of the bolt handle. -
The 2nd Slag gunman at the beginning of the film discards his Remington 870 short shotgun and uses a Ruger AC556 with an aftermarket synthetic pistol grip stock. Later he throws down the AC556 from his perch on a L.A. Billboard. It is replaced with a rubber casting of the weapon at this point.
Micro Uzi
Carried by the human henchman during the first robbery heist, in reality an execution.
Beretta 92FS
Matthew Sykes (James Caan) at the beginning of the film uses a Beretta Model 92FS.
Smith & Wesson 5906
Det. Bill Tuggle (Roger Aaron Brown) carries a S&W 5906 pistol at the beginning of the film.
Freedom Arms Model 83 Revolver
Upset over the death of his human partner, Det. Sgt. Matthew Sykes (James Caan) trades out his Beretta 92FS and picks up a Freedom Arms Model 83 Revolver chambered in .454 Casull. The Model 83 appears to be the premiere grade. Freedom arms offers two grades of the Model 83 (and the shorter barreled Model 97). The Field grade has a matte stainless finish, the Premiere grade has a high polish stainless finish.
Remington 870 Shotgun
A full sized Remington 870 police shotgun is used by Det. George Francisco (Mandy Patinkin) when he is pursuing the mutated slag monster. Also a short barreled Remington 870 with a synthetic black pistol grip (with no stock) is used by the 2nd Newcomer robber at the beginning of the film.
Commercial M1911A1
Carried by Rudyard Kipling (Kevyn Major Howard), better known as Rafterman in the film Full Metal Jacket. Kevyn retired from acting in 1999 and is a successful (and talented) photographer working in Los Angeles.
Smith & Wesson Model 586
One of the human henchmen carries a 4" barreled Smith & Wesson Model 586 (.357 magnum) Revolver.
Smith & Wesson Model 10
A female police officer at the Police Target range is seen using a standard Smith & Wesson Model 10. It is not unrealistic for a woman officer (in the 1980s) to choose a smaller caliber round than her male counterparts.
Smith & Wesson Model 27
Smith & Wesson Model 28
Unknown Snub Nose Revolver
Detective Francisco (Mandy Patinkin) pulls out his backup revolver, but it is too dark to determine what it is.