Audio problem: While at the range, Jamie takes Frank's revolver to the line and fires it. The last 2 shots you can hear the casings hitting the ground, but not on the first 3 shots. The last 2 shots are from another camera angle. Revolvers don't eject the casings, so we shouldn't hear them landing.
Audio problem: In the final scene Danny executes the man who killed his brother. Danny is armed with a snub nosed revolver. When he pulls the trigger, the sound of a shell casing bouncing on the floor is heard. A revolver does not eject empty shell casings.