In regards to the single-action revolver in the holster in pictures from the set of Tremors 5. (Michael Gross) can be quoted saying the script called for a Colt Single Action Army but what they ended up with was a replica in a "Cattleman's" configuration with a slightly longer barrel that Burt derisively calls a "pop-gun." Naturally, though, he proceeds to "do what he can with what he's got. If I had to guess presently based on what Michael Gross said, its a Uberti Cattleman with 5-1/2" Barrel.
Rifles
Winchester Model 70
Burt Acquires a Winchester Model 70 in 30-06 Springfield which he uses on his hunt to his dismay of not having enough gun for the job.
Birmingham Small Arms Lee-Speed Sporter
Burt is somewhat concerned and disappointed when he discovers he is forced to hunt Graboids with a .303 Caliber BSA rifle, Burt uses it a few times throughout the movie.
Unknown Rifle 2
While stateside, in Perfection Valley, Nevada. Burt hosts an episode of a survivalist reality show and totes around this presently unknown bolt-action rifle.
Battle Rifles & Carbines
Heckler & Koch HK91
Travis (Jamie Kennedy) easily convinces Burt (Michael Gross) that he needs to go to South Africa too, giving him the HK91 in exchange. The HK91 has a special place in Burt's heart as it was the gun Heather Gummer requested from Burt when she left him.
Vektor R5
Burt is given a customized Vektor R5 in the trailer.
Shotguns
Unknown side-by-side Shotgun
Travis Welker(Jamie Kennedy) appears to be toting a side-by-side in the Tremors 5 promotional image.
Armsel Protecta
The Protecta is used by Den Bravers (Ian Roberts) when he goes on a rescue mission.
Machine Guns
FN MAG 58
Burt Gummer (Michael Gross) uses a FN MAG belt-fed machine gun in the upcoming film, appears to have a synthetic buttstock.