Otherwise...stat it as rifle, however many shots you like, does 1 pt damage like a bullet, and has the stunning effect of a taser or stun gun from the main book.
Realistically? Single shot.
Cinematically? At least equivalent to a bolt-action .30-06, like the M1903. If *I* was the red-shirt tasked with maintaining order in Dinotopia, I'd want a tranq-gun similar to what was suggested for the .458 SOCOM M16: 10 big trang rounds I can shoot out really fast. Paraphrase the scene in Age of Ultron: "GotosleepGoToSleepGOTOSLEEP!"