Killer Karl (Chad Bannon) one of the two robbers in the opening scene uses a Colt Diamondback to attempt to rob Captain Spaulding (Sid Haig).
Colt Lawman MK III
Captain Spaulding (Sid Haig) pulls a Colt Lawman MK III revolver from under his counter to take out the two robbers. It is identifiable by not having a shrouded ejector rod, and by its sights. It is likely the same Lawman used by Sheriff Wydell (William Forsythe) in The Devil's Rejects.
Ruger Redhawk
The second robber, Richard Wick (David Reynolds), appears to carry a stainless Ruger Redhawk revolver with stainless steel finish and a 7.5-inch barrel. This was previously identified as a Ruger Security Six with a 6-inch barrel. However, it can be differentiated from a Security Six by its large chambers and non-knurled ejector rod. The ejector rod housing is also not as thick as it is on the Security Six. The revolver being a powerful .44 Magnum also explains why Richard threatened to "blast a hole the size of a Kansas City watermelon" through Captain Spaulding's face.
In a continuity error, Mama Firefly's Colt Trooper becomes a Smith & Wesson Model 36 "Chief's Special" when she shoots Wydell.
Shotguns
Sawn-Off Single Barrel Shotgun
During one of the random intermission scenes, a man known as Lewis Dover is wielding a Sawn-off Single barrel shotgun, it is more than likely an H&R or New England Model shotgun.
Mossberg 500
Rufus uses a Mossberg 500 Shotgun to shoot out the teenagers tire on their car