When the cop visits Karen's house, he notices and picks up the revolver. He then looks at the cylinder. The gun had been recently fired and a trained cop would notice the gun powder residue on the chamber.
Charlie Farrow is struggling with a cop in a shopping mall. The cop's hat is knocked off, but in the next scene it is back on while they are still struggling.
Near the end a Vehicle knocks over a power line (with transformers) in the middle of the amusement park, with the power lines shorting and pulling loose. However the entire park still has full power.
Even with the extended magazines, there are far too many shots fired from the Uzi near the end of the film.