Producer Joel Silver's contract with Warner Bros. - who were distributing the picture - was about to come to an end when Bullet to the Head was in post-production. The relationship between the studio and Silver had deteriorated after Silver accused Warner of botching the release of Sherlock Holmes: A Game of Shadows (2011).
Wayne Kramer was originally hired to direct in February 2011. After clashing with Stallone over the tone of the film, he left the production and was replaced by Walter Hill on April 11, 2011.
When Bonomo meets Kwon in the bar for the first time, Bonomo fills up his glass with his favorite 2 Bullet bourbon. He then drinks about half of the glass. While talking to Kwon he brings the glass back up to his mouth for another drink and the glass is full again.
Cop Taylor Kwon is shot twice into his right shoulder. In the last scene his partner James Bonomo meets Kwon in a bar. After Kwon suggests James cease his criminal activities, James gets up to leave. He taps on Kwon's left shoulder commenting 'did that hurt?', even though no harm was done to this shoulder.