Everyone here seems worried about the big T-Rex, but you should be more worried about the raptors. They are extremely smart from what we can tell, very agile and would be a severe threat to humans if they existed in this age.
The raptors there (likely Velociraptor mongoliensis) would have more likely gone after prey its own size. Some of the other larger dromaeosaurs, such as Utahraptor, Deinonychus and Achillobator, would be more dangerous and worrisome. In the JP scenario, if the Velociraptors don't run when they see you coming, pop a couple of rounds over their heads. If they still feel adventurous, slide the Mk-17 into full auto and get ready to replace some mags or fire off a shotgun round from the Mk-13. As for the larger ones, the most recent publication on dromaeosaurs discusses the likeliness of them being ambush predators rather than running down their food like a Troodon would have. Again a hollow point or other game round would work fantastic, say, about 180 gr if not heavier. A shot to the head, neck, and thorax would be a game ender for them. Since they have some fairly hollow-ish bones, a round hitting them would fragment that bone and send shards throughout the soft tissue. Looking at the Remington Ballistics calculator, a 180 gr round at 100 yards will put out at least 2000 ft-lbs of energy.
The next step would be to pluck, gut, and butcher them. A nice bed of coals about 400 degrees. A couple of cold Dos Equis with lime. Maybe some of the ZS folks from Texas could airdrop some BBQ sauce.
_________________ ZSC:002 Pittsburgh Area Chapter Officer US Marines- Making Martyrs since 1775