According to the movie's script doctor William Goldman, Clint Eastwood, Robert Redford, and Harrison Ford passed on the movie. These men would have fit the literary Bob Lee Swagger's age a bit more closely than Mark Wahlberg (born in 1971). Author Stephen Hunter introduced Swagger as a Vietnam veteran in a 1993 novel, taking place in 1992; however, to accommodate Wahlberg's age, this film has Swagger active in Africa in the 1990s, instead of Vietnam in the 1970s.
(at around 57 mins) The website to which Nick Memphis (Michael Peña) is given a link in the chat room, precisionremotes.com, is real. It is the website of Precision Remotes, a Richmond, California, company, which designs and manufactures remote-operated weapon and surveillance platforms, such as the one featured in the film.
Mark Wahlberg had to lose twenty pounds, to give Bob Lee Swagger the slim and ripped look of a field sniper, to make the film more realistic.
The large caliber rifle that Swagger owns, with which he is framed, is a Cheyenne Tactical M200 Intervention. It fires a .408 caliber projectile accurately out to and beyond two thousand meters. The CheyTac M200 is also available with a Long Range Rifle System, which consists of a laser range finder, magnifying scope with night vision capability, and a weather-sensing module, all of which interface with a PDA running ballistics calculation software.
The dog featured in the film as Bob Lee Swagger's companion was trained by owner Drew Thompson. The dog's real name is Logan. He is a Bernese Mountain and English Mastiff cross. Thompson states that "he is easily the smartest dog I have ever trained".