Corrected entry: In the beginning credits, Harry says "This is the 44 magnum, the most powerful hand gun in the world." However, later when he's at the range with David Soul and the other cops, he is asked about his gun loads and he says he uses .357 lite magnum.
Corrected entry: The bomb planted in Harry's mailbox is set to explode when the mailbox is opened. So why does it need a timer attached to it?
Correction: As a backup detonator.
Corrected entry: During the final scenes of the film, Clint Eastwood in his Ford is being tailed by a policeman on a motorcycle. The policeman pulls out his gun and fires a few shots with his right hand. The motorcycle's throttle is on the right hand side of the handlebars, but still this bloke somehow maintains speed.
Correction: Some law enforcement agencies in the US used motorbikes with a left handed throttle for such use. There are also throttle locks.
Corrected entry: During Davis' combat pistol round, we see him shoot a standup target from the target's perspective. He fires twice, but we see a second bullet hole pop out before the second shot is fired for a total of three holes from only two bullets.
Correction: The target was shot at once prior to the camera cutting to the target's perspective, so in total it was hit 3 times with 3 bullets, thus the 3 holes.
Corrected entry: During the final car chase, there are multiple sets of skid marks on the winding road from previous takes.
Correction: This type of "mistake" has been posted and corrected for numerous different movies. This is San Francisco, where tire tracks on the street are not entirely unusual. It isn't all that unusual to see tire tracks on the switchback part of Vermont Street, on which part of the car chase happens.
Correction: When at the range with the rookie traffic cops, Harry says he shoots "light specials" out of his 44 magnum which provide more control than a .357 magnum with wad cutters.