Character talks about MREs having one gram of fiber. MREs were not used in Vietnam. In Vietnam they used C or K rations. MREs were not used until the 1980s.
Character refers to a M-2 Browning .50 caliber machine gun as "gas operated". Those weapons are recoil operated.
Nobody in the military would say "over and out" in radio communications The correct ending of a contact is simply "out"
The F111 visible at the airbase at the start of the movie was not deployed in Vietnam until 1968.
The version of m16 rifle used in the movie are of a late vintage, this version was not in service in 1966.
The Colonel keeps calling the Captain "Sir", but then again, he calls everybody sir, including the corporal.
The UH-1H Huey helicopter has a small radar bulge in its front. This development came at a later date and was not available in the Vietnam era helicopters.
The character of "Miller" calls himself "Leftenant Colonel Miller" - he was a full Colonel. American Soldiers/Marines/Sailors/Airmen use "Lieutenant" - literally meaning "holding the place of" in French. He also wears the eagles of a full Colonel on his uniform, but he wears them incorrectly.