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.

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.

Swagger's name may be a play on the term "SWAG". In sniping terms it stands for "Scientific Wild Ass Guess", a quick calculation made on the fly.

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.

During the mountain top confrontation, Swagger kills one of the snipers by shooting the counter-sniper through his rifle scope. This is likely based upon an infamous kill by renowned U.S. Marine Corps Gunnery Sergeant Carlos Hathcock during the Vietnam War.

While originally aimed to have a PG-13 rating to attract a wider audience, the producers wanted the film to have an R-rating after Mark Wahlberg signed on for the lead.

Swagger sees the last sniper when the sun glints off his binoculars. Carlos Hathcock spotted the sniper sent to kill him when the sun glinted off his scope. Hathcock shot at the glint. His bullet went through the scope and hit the sniper in the eye, which means that Hathcock, like Swagger, was in the other sniper's sights. They shot quicker and lived.

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.

Keanu Reeves was the original choice to play Bob Lee Swagger.

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 X. Drew states that "he is easily the smartest dog I have ever trained".

Athens, Tennessee, the residence of the firearms expert Swagger and Nick visited, was the location of the "Battle of Athens", where in 1946, armed citizens removed the corrupt local government, and restored free elections.

Swagger's wristwatch is a Suunto Vector, a digital watch made in Finland. Besides telling time, it also has an altimeter, barometer, and digital compass.

Eminem, aka Marshall Mathers, turned down the villain role.

Stephen Hunter, the author on whose novel the film is based, is a Pulitizer Prize winning film critic for the Washington Post.

The theatrical trailer features a scene not used in the film, where a small jet is blown up via remote control.

The book that Bob Lee Swagger reads in his house is the 9/11 Commission Report.

The portraits on the walls in the room where the conspirators meet, in Langley, Virginia, are all of Republican Presidents.

Throughout the film Swagger does change which eye he uses to scope his targets. This is mentioned by a previous poster as cause for him to miss some of his shots. There are two reasons why Swagger could still make all his shots, even with switching which eye he sights with. One possible reason is that there is a small percentage of the population who are not eye dominant. This is uncommon, but is the case in some instances and means they can shoot equally well with both eyes. The most likely reason in Swagger's case is that even if he is eye dominant, you can learn to shoot with both eyes. Being he is a HIGHLY skilled sniper with extensive training, he probably did learn to shoot with both eyes.

FBI Agent Nick Memphis is saved from a sniper's bullet, by concealing a piece of plate iron under his clothing. Clint Eastwood's Man with No Name used the same trick in A Fistful of Dollars (1964).

The Chevrolet Suburban that Swagger asks if it's the big block 8 litre V8 engine is actually a 5 litre engine. The vehicle's aluminum's rims give it away.

This was the final film to play at the landmark Mann National Theater in Westwood, California, before it closed on April 20, 2007.

The sudden cut to the Montana Senator shows him firing a shotgun near the camera in hunting gear, very similar to Dick Cheney.

The left-wing website zmag.org can be seen on Swagger's laptop while he is reading the 9/11 Commission report. Zmag publishes articles by, amongst other academics, Noam Chomsky.

Shipped to some theaters under the name "Stars".

The author, Stephen Hunter, was close friends with Dexter Swagger, whom he worked with at The Baltimore Sun. He thought the name was perfect for his character. He stated this in the eulogy at Dexter Swagger's funeral.

This film is the third in which Wahlberg has portrayed a character with a name that's a variation of Robert. The first is The Perfect Storm (2000), in which he portrayed Bobby Shatford, and the third being Four Brothers (2005), in which he portrayed Bobby Mercer.

Actor Ned Beatty as Senator Meachum gave his reality speech about no Suni no Shites and only so many seats at the table to Bob Lee Swagger played by Wahlberg. Beatty also gave a similar reality speech about no religions and no Arabs in the 1976 film "Network" to actor Peter Finch as newscaster Howard Beale.

Swagger wears a Philadelphia Eagles jacket and hat when he fights the two police officers. Mark Wahlberg played Vince Papale in Invincible, a film about a bartender who plays for the Eagles.

The ranch shoot-out scene was scaled back, due to the violence. The scene in which Bob Lee Swagger (Mark Wahlberg) kills a bodyguard with a knife to the throat was scaled back tremendously. Originally, the knife was supposed to exit through his nose, causing blood to spray on Swagger. The scene was cut because the MPAA deemed the scene too brutal.

The FBI Agent helping the shooter is wearing a Che Guevara t-shirt in a scene.