Factual error: The crew gasses out the ant hill by dropping chemical grenades into the hole. But there are two reality mistakes about the grenades: 1) chemical grenades do not explode; they spray their contents into the area; and 2) considering the size of the ants, the size of their nest must be gigantic, and therefore, it would take more than a hundred grenades to flood it completely with cyanide gas.
Factual error: Grandpa Johnson's .30-30 Winchester rifle was apparently bent by the giant ants during their attack on his store. But as we can see later, the ants' mandibles are too thin and too curved to provide enough gripping and leverage area for bending a metal rifle barrel that severely.
Suggested correction: Impossible. When Ben Peterson is killed near the film's end, you can see that the ant's mandibles leave too much space even as they clamp shut. And their slender form is made for grabbing bites, not sturdy enough for crushing jobs.
That's just what I was talking about, if not quite correctly worded.
Factual error: In order to keep the giant ants inside the New Mexico nest, the protagonists bombard the entrance hole with phosphorus shells. Phosphorus burns at an average temperature of 5,000° Farenheit. At this temperature, the heat from the shells should have fused the sand around the entrance hole to glass (the threshold for this process is about 4,200° Farenheit), yet the sand remains unchanged.
Factual error: When they put the pin on the map of Texas to mark the city of Brownsville, they are hundreds of miles off in West Texas near the city of Alpine. Happens around the time the patient who crashed the plane is interviewed in the hospital in Brownsville.