Couple of things I noticed.
The timeline of the movie states it takes place in 1964, but the unit patches on the sleeves of the soldiers are MAAG patches (Military Assistance Advisory Group) which was the predecessor to MACV (Military Assistance Command, Vietnam), however right now Im reading a book about the Special Forces and CIDG in Vietnam and it states that MACV was activated in 1962, which would make their patches incorrect.
Also, when Lt. Wattsberg walks into Major Barkers office to tell him that they got the air support they needed, he was reading a book called Seven Firefights in Vietnam, which was first published in 1970.
Both of the books I mentioned, Seven Firefights and the Special Forces book can be found here, http://www.army.mil/cmh-pg/online/Bookshelves/VN.htm, along with many online books making up a library of publications called Vietnam Studies.
And nobody needs to tell me I have no life, I already know, and I still like the movie, mistakes and all.