Corrected entry: The silencer devices on the rifles in the movie can only be used on a weapon that utilizes .45 calibre ammunition. The rifles utilize 5.56mm.
Corrected entry: I know being a bad shot isn't necessarily a plot hole, but several times the cops outside have a direct bead on Sgt. Roenick (as he runs in and out of the building) through their telescopic sights at almost point blank range, and miss completely. Likewise, a big deal is made in the laser site scene earlier. One essentially cannot miss with a laser sighted weapon, yet these cops cannot hit the broad side of a barn. This really stretches credulity to the nth degree.
Corrected entry: When Roenick and the others emerge from the underground sewer, he uses one hand to effortlessly push aside the manhole cover. Large manhole covers weigh several hundred pounds - far more than can be moved with one hand.
Corrected entry: It is snowing heavily during the drive in the bus near the start of the film, yet in the shot when you see out the front of the bus from the driver's view, there is no snow falling at all.
Corrected entry: During the first 3/4 of the movie, the wind is blowing very heavily (the snow is flying to the side), but when the snipers aim they aim directly at the different people. Real snipers would know you had to move a bit to the left or right to make up for how far the bullet would be blown off course. The directors chose not to have them aim off-center because it might be confusing, seeing someone shoot four feet to the left and hit them right in the head.
Corrected entry: The scope on Bishop's rifle retains the protective covers on for the length of the movie.