There's actually been a study on the skull and jaw structure of pit bulls compared to other types of dogs. Pits do not of locking jaws, nor are their jaw muscles significantly stronger than other dogs'. What makes pits and other fighting breeds so "dangerous" is that they have an extremely high pain threshold and an incredible tenacity.
Very right, pits jaws are no different than any other dogs.

They are in the group terrier, which in latin means terror. Most terriers act very "feisty" such as Jack russell terriers, schnauzers, etc..

Any good pit rescue will tell you to never to bring pits to a dork park, because if there is a fight, there is almost no way you can get a pit off except with a bite stick. They are just incredibly determined when it comes to holding on, especially when playing with tug toys, like most terriers. Most are very nice, but there are some that just strongly dislike other dogs.

Pure APBT's have a very high possibility of becoming dog aggressive around the age of 2 years old, because fighting is in their genetic history. APBT are closely related to the fighting strain of dogs, while American Staffordshire terriers are less prone to dog aggression. Many owners socialize their dogs wonderfuly and then they say it's like a light switch being turned on. They just stop liking other dogs, and you can't completely get rid of it, but you can manage it and the dogs can usually have other doggy friends that they get along with.