Burt (Michael Gross) is given a Single-Action revolver in .45 Colt by Erich Van Wyk (Daniel Janks) when his weapons he requested got held at Customs.(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. Burt proceeds to carry the revolver throughout the film and does use it.
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
Dr. Nandi Montabu (Pearl Thusi) gives Burt (Michael Gross) a customized Vektor R5 when she thinks it may be more useful on the creatures then what weapons Burt has. Burt uses it to open fire on creatures. Erich Van Wyk (Daniel Janks) can also be seen in possession of the rifle but it is lost later on. .
The Protecta is used by Den Bravers (Ian Roberts) when he goes on a rescue mission.
Machine Guns
FN MAG 58
Both Burt (Michael Gross) and Travis (Jamie Kennedy) use a FN MAG belt-fed machine gun in the film, it appears to have a synthetic buttstock and was given to Burt by Den Bravers (Ian Roberts).