A US marine fighting in the Middle East inadvertently falls in a hole that happens to be a time portal and is teleported in the Cretaceous era, 70 million years in the past.
Our Marine is equipped with a M16A4 and the standard Marine equipment (grenades, binoculars etc...).
When wakes up, he is in an open forest, unharmed. A T-Rex wandering nearby unfortunately spots him and decides to have a bite from this strange looking monkey.
Does our poor Marine stand a chance? Can he somehow scare off or even kill the T-Rex with his weapons?