It’s misleading marketing at best. All the posters and advertisements seem to spotlight Vince Vaughn, comedian and movie star, standing center stage. But there’s about as much of Mr. Vaughn in “Vince Vaughn’s Wild West Comedy Show” as there is blood in “There Will Be Blood” — which is to say, not much at all.

Instead, what we have here is a perfectly pleasant road trip docucomedy, stretched and dismembered to fit the dimensions of a feature film, and branded with a recognizable name in the hope of luring unwitting fans of “Wedding Crashers” and “Swingers.”

In September 2005, Mr. Vaughn decided to organize a 30-day traveling comedy marathon, ostensibly in part because these sorts of “Old West variety shows” are rarely seen in modern America. Turning to the talents working Los Angeles’s Comedy Store, Mr. Vaughn gathered a group of four comedians to board his cross-country bus. On paper, no doubt the idea looked promising: a traveling variety show, mixed with a behind-the-scenes travel diary of five hilarious guys as they traverse the South and the Midwest, from Los Angeles to Chicago.

Each comedian brought his own brand of shtick. Ahmed Ahmed leans heavily on his Egyptian heritage, delivering jokes that highlight the ways racial stereotypes have escalated and evolved — and in many ways remained the same — since the attacks of September 11, 2001. The blue-collar ying to Mr. Ahmed’s Middle Eastern yang is John Caparulo, who grumbles and grouses through his routines with a suitably “working-class” gravelly voice. Bret Ernst is the self-anointed East Coast “guido,” turning his comedic sights on all things involving nightclubs and New Jersey.

In terms of personality and complexity, the most watchable of the crew is Sebastian Maniscalco. Onstage, he offers one hilarious aside after another, targeting the peculiarities and contradictions of the modern man and skewering accepted ideas of masculinity and testosterone. But offstage, his odd travel habits and humility make him an even more intriguing fellow. In awe of both Mr. Vaughn and his Comedy Store colleagues, and clearly overflowing with excitement about this 30-day adventure, Mr. Maniscalco is ecstatic about what this “Wild West” road trip may mean for his burgeoning career. In his backstory, we find a slice of the drama that is woefully missing from the remainder of this puff documentary.

Mr. Vaughn is featured prominently during the movie’s first few segments, as are a few notable names (actors Justin Long and Jon Favreau are called to the stage), but they are increasingly pushed to the fringe by first-time director Ari Sandel, who shifts to the new voices as they try to find their rhythm.

The second chapter of the documentary digs into their histories and the stress of life on the road. All four second-tier comedians expound on where and when they developed their material, and we watch the few minor arguments that break out among the group as the days and cities begin to blur. In one fascinating scene, we witness a comedic bit crash and burn onstage as a rural audience turns on one of the comedians. It is here we see the psychological stress lurking behind the laughs and gain real insight into just how hard these guys work, how vulnerable they feel when chucking out punch lines night after night, and how ruthlessly they judge their own material.

But that kind of insight is in short supply, as the second half of “Wild West” devolves into a sloppy potpourri of subplots. City to city, Mr. Sandel turns each destination into a fleeting montage, chopping up comedy routines with sideline confessionals and selling his subjects short as both comics and men.

It sure looks as if everyone involved with Mr. Vaughn’s “Wild West Comedy Show” had a grand old time; Mr. Ernst goes so far as to dub it a “spring break for 30-year-olds.” But if “The Real Cancun” taught us anything — and believe it or not, it did — it’s that one spring break does not a movie make.