This film (along with several others) is somewhat based on the story of US Marine Corps sniper Carlos Hathcock, who took out a Viet Cong sniper who was stalking him by firing a round through the man's scope, sending the bullet into his brain. The story has been labeled a "myth" by some, but the incident was observed by Hathcock's spotter, John Roland Burke, who surveyed the scene after the kill. Given the flight time of rounds at long ranges, both snipers could easily have killed one another. The enemy rifle was recovered and the incident is documented by a photograph. After an investigation, the Marine Corps confirmed the incident and registered the kill to Hathcock.
The film was marketed two different ways. The international trailer--produced by the independent financiers behind the film--focused more on the psychological and thriller elements of the story and showcased the struggle between Beckitt and Miller. The US trailer, cut by TriStar, who picked it up, was accompanied by the muscular score from Terminator 2: Judgment Day (1991) and focused more on the action elements, highlighting the chase and shootout sequences.
The weapon used by Billy Zane in this movie is not an H&K PSG-1, an expensive precision semi-automatic rifle commonly used by special forces snipers. It is an H&K SR-9 TC , a similar but cheaper version of the PSG-1 that was designed for civilian sales.
If you look closely at the locomotive of the train that inserts Beckett and Miller, the QR symbol of the Queensland Rail can be seen on the side. Queensland was the state of Australia where this movie was shot.
The trivia item below may give away important plot points.
Thomas Beckett (Tom Berenger) and Richard Miller (Billy Zane) have a discussion about being from the same place in Montana. In fact, the actors were both born in Chicago, Illinois--Berenger in 1949, and Zane in 1966.