I read a book in which one of the caracters was really good at throwing his CRKT M16, and i was wondering if it is possible and if so how to do it.
For some odd reason, I've had better luck with handle-heavy knives (folders) than balanced throwing knives. Adds considerable power when thrown by the blade -- although, if your distance is wrong, it is unlikely to connect point first. Best to attempt an "underhand chuck" at close range (within 5 feet) if you want a better chance of making it stick. Multiple layers of corrigated cardboard make a good low-impact target for a folder -- if you throw a folder repeatedly at a tree, it will eventually fall apart.
One thing you need to know about "action adventure" authors (which includes screenwriters) is that many of them are living in a fantasy world, have no experience with the subjects they're writing about, and often depend upon the inaccurate works of other action-adventure writers for "research."
Here's a well-known story about combat knife throwing which may actually be true:
Back during the Vietnam conflict, a congressman went to a pub where he encountered a man who claimed to have recently returned from Vietnam, where he saw combat with a Special Forces unit. After much beer was consumed, this alleged soldier wove a number of tall tales about the many enemy which he'd silently dispatched with an expertly thrown knife. This so impressed the congressman that he proceeded to contact a General and proposed that all Special Forces troops take a class in combat knife throwing. This soon came to pass. When the SF troops assembled for the mandatory class, an instructor would come out and say, "The purpose of this class is to instruct you in the art of combat knife throwing. If you throw your knife at the enemy, it is unlikely to strike point first. It is more likely to bounce off, make him angry, and give him a weapon. Never throw your knife." And that would conclude the class.
Practitioners of Kali, who advocate carrying multiple knives which are intended to be thrown, do so with the understanding that it is only meant as a distraction. It is true that some people have successfully dispatched other men, or even wild game, with thrown knives -- although such occurances are extremely rare. During WW2, a Native American infantryman was awarded a medal for killing an enemy soldier with a thrown knife from over 100 feet away . . . I do not believe that is true, even though a number of others supposedly witnessed it . . . sorta like the "true" stories of the fellow who could kill a deer with a thrown playing card. If you throw a knife at a distant moving target under stress -- and actually hit what you're aiming for -- there's only a 25% chance that it'll stick. Try throwing a knife at a stationary target from a variety of distances to see how difficult this can be. Not easy like in the movies, and it is highly unlikely that an enemy pierced with a thrown blade would instantly drop without a sound -- more likely he'd pull it out and chase you with it!