Corrected entry: Matt Damon's M4 rifle does not have a magazine in it while he talks to the CIA officer at the hotel.
Corrected entry: When Roy is talking in Marty's office, there are clocks on Marty's wall representing the time in different parts of the world. The minutes on the clock are all different, and in real life, only the hours are different.
Correction: Almost all time zones are one hour, but there are some time zones that are only half an hour different. Much of Newfoundland and Labrador have a half hour time difference from Atlantic Standard Time, Venezuela is a half hour difference from neighboring countries, and Nepal has a 15 minute time difference from Bangladesh, for a couple of examples.
Correction: Here's the reason why: at this point in the movie, he entered a secure U.S.-controlled building. Loaded weapons are not allowed in such areas, and so Miller probably turned in his magazines at the checkpoint before entering the building.