Bob Lee Swagger can shoot a rifle with a precision that eludes the script that brings him to the screen.

On top of that, Swagger - the hero of the new thriller Shooter - doesn't really live up to his name: Far from being a braggart, he's one of those laconic military guys who dutifully served the country that eventually let him down. Disgruntled after a stint in Ethiopia, Swagger retreats to a mountain hideaway. He trusts no one, except maybe his dog.

Shooter provides Mark Wahlberg with one of those muscular Rambo-like roles in which artillery substitutes for drama. In the hands of director Antoine Fuqua (Training Day), Shooter blasts through lots of action, but fires blanks when it comes to its convoluted plot.

Here's the drill: After spending more than a year living in the backwaters, Swagger is contacted by a military officer (Danny Glover) who asks him to accept (what else?) one final mission.

Glover's character, who seems to be connected at the highest levels, explains that the U.S. has gotten wind of a planned assassination of the president. As a bona fide sharpshooter, Swagger is supposed to help the government thwart the attempt on the president's life.

It's not giving away much to tell you that a murky series of developments puts Swagger on the run. While in flight, he seeks help from a woman (Kate Mara) who was married to one of his Marine buddies. He eventually enlists the sympathy of an FBI agent (Michael Pena), whose standing at the bureau recently has slipped.

Wahlberg has no trouble flexing this kind of acting muscle, but Pena delivers the movie's most surprising performance. Pena, who played a trapped police officer in Oliver Stone's World Trade Center and who portrayed a Los Angeles locksmith in Crash, does a fine job of creating a smart, slouching character with a dogged commitment to discovering the truth.

Built around a conspiracy that reaches high into the government, the movie cloaks itself in off-the-rack cynicism that goes something like this: There are people in the government who will do anything to benefit themselves, even if it means killing innocent people. That may sound controversial, but in Fuqua's hands, it comes off as generic paranoia that hardly merits a shudder.

Fuqua stages ample action, but can't paper over the movie's many plot holes. Shooter winds up being the movie that would have left us scratching our heads about Wahlberg's choices had he actually won the best supporting actor award for his terrific work in The Departed.

Although located off-screen, some irony can be found here. Stephen Hunter, who writes film reviews for The Washington Post and who has won a Pulitzer for his efforts, wrote Point of Impact, the novel on which Shooter has been based.

Of course, Hunter, who'll no doubt recuse himself from reviewing duties here, didn't write the screenplay for Shooter. That job fell to Jonathan Lemkin (Lethal Weapon 4), who writes scenes in which Swagger must deal with a couple of bullet wounds that would have killed a lesser man and which don't do much to make the story any more believable.