The Beretta 92FS is used in the film by US Army soldiers (standing in for the M9) and militia men during the film as well as by Dr. Wesley McClaren (Steven Seagal).
M1911A1
A nickel plated M1911A1 with ivory grips is wielded by militia leader Floyd Chisholm (Gailard Sartain). Dr. Wesley McClaren (Steven Seagal) also handles this weapon.
The AKMS is used by various militia men during the film.
M16A2
Both militia members and U.S. Army soldiers wield M16A2s through the film. Much like the XM177s in the film, which are actually Olympic Arms K3B clones, these rifles are also likely the Olympic Arms K4B.
Olympic Arms K3B CAR
Many U.S. Army soldiers and militia members in the film use CAR-15-style rifles which resemble the XM177E2. Upon close inspection, these are actually the Olympic Arms K3B CAR, which is the Olympic Arms commercial XM177-pattern clone sold in the U.S. until the mid-1990s. Notably, they all feature M16A2-style receivers (not found on any genuine XM177 variation) and long "mock" XM177 flash hiders that lack sound suppression capabilities.
The Remington 870 is wielded by a couple militia men in the film. In a courtroom scene early in the film, Floyd Chisholm (Gailard Sartain) is seen sawing down the barrel on a Remington 870 on a videotape played before the court, which is used as evidence to charge him with a National Firearms Act violation.