The double rifle is a type of sporting rifle often associated with African big game hunting, and is colloquially known as the elephant gun. This type of weapon has two barrels to allow firing of two shots in rapid succession without reloading, and often has two triggers for redundancy.
Roland Tembo can be seen with this rifle on Isla Sorna, his rifle being hammerless and uses a side by side barrel configuration, using two triggers. He intended to use this rifle for hunting the adult male Tyrannosaurus rex, and it almost never left his possession. The one time he clearly left his weapon unguarded, Nick Van Owen used the opportunity to sabotage the hunter’s attempt to bring down his quarry by removing the slugs and the powder charges. This resulted in two dry clicks later, when the weapon was needed to stop the Tyrannosaurus attack on the stranded expeditions’ encampment, much to Tembo’s dismay.