Factual error: Before SG-1 switched to P90 PDW's, they carried MP5 submachine guns. They were often shown with a full magazine taped upside down to the one in the weapon, so that to reload, all they have to do is remove the magazine, turn it over and insert the full one. Team members were also shown doing just that in several fight scenes. Problem is, real special ops troops are specifically taught in training never to do this. It's far too easy to damage the lips on the spare magazine, rendering it useless. There are clips that will hold magazines upright side by side, but its easy to see on screen they weren't using them.
Factual error: Earth's Stargate is dialed up more then once in series 1. Mostly in the first episodes, the passive gate is also shown with a rotating dialer ring when being called. This is not correct. The called gate only illuminates the chevrons. (This is classed as a 'factual' mistake within the show, not a 'continuity' error, and the option to change type has been removed.)
Factual error: The escort for Colonel O'Neill is wearing both Major and Staff Sergeant rank insignia. Probably what the writers thought was a "Sergeant Major", which does not exist in the Air Force. Major is a commissioned officer, sergeants are non-commissioned officers.
Factual error: Carter claims that the gates shift position because of the expansion of the universe. Gravity sources within a galaxy completely compensate for such expansion. The gates would still experience "stellar drift", which is mentioned earlier in the same episode. Stellar drift occurs because stars orbit the galactic center independently.
Factual error: In the scene where O'Neill and Maybourne are looking up NID flight plans, the plan viewed on the computer lists the destination airport as Minot Airport Base, but provides the airport code for McCarran International Airport (KLAS). It also lists non-existent runways, as in runway headings that do not exist anywhere in the world. (00:24:15)
Factual error: At the end of the episode General O'Neill is introduced to Joe's wife. He is introduced as General O'Neill, but his insignia on his dress blue uniform is a Colonel - an eagle, not a General's star.