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
Unknown Rifle
Possibly a Lee-Enfield Sporterized rifle, maybe a big-bore conversion?
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
Vektor R5
Burt is given a customized Vektor R5 in the trailer.
AK variant 2
Shotguns
Unknown side-by-side Shotgun
Travis Welker(Jamie Kennedy) appears to be toting a side-by-side in the Tremors 5 promotional image.
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.