It’s survival of the fittest this weekend at the crowded late summer box office.

For now, it looks like there’s enough gas left in the tank for the geriatric action heroes of “The Expendables 3” to outflank the rising comic stars of “Let’s Be Cops” and the youthful cast of “The Giver” at the weekend box office. But just barely.

“The Expendables 3” will likely rack up a solid $23 million to $25 million when it debuts in 3,209 theaters. The film tries to inject freshness into the Reagan-era formula by excavating a few other relics of ’80s and ’90s abs and ammo flicks, such as Mel Gibson and Harrison Ford, but the Sylvester Stallone series is starting to show some wrinkles. Part one fired up with a $34.8 million debut in 2010 and the 2012 follow-up scored a $28.6 million opener. Inevitably, some fatigue may set in, analysts say.

“When you hit three-quel status, unless you’re adding something new to the ballgame, the formula looks too similar and people get tired,” said Jeff Bock, an analyst with Exhibitor Relations.

There’s also the question of how much piracy will impact “The Expendables 3.” A high-quality copy of the film leaked to piracy sites three weeks ago and was downloaded 189,000 times over a 24-hour period. The last time a similar breach occurred was in 2009, when a New York man uploaded an unfinished version of “X-Men Origins: Wolverine” to the internet a month before it hit theaters. The film bowed to $85 million, so the impact was de minimis, but it’s not clear if in the ensuing years, piracy has become more widespread and damaging to box office prospects. If it does poorly, look for disgruntled SOPA and PIPA advocates to shake their “I told you so” fingers.

REVIEW: “The Expendables 3”

Overseas, where Stallone, Arnold Schwarzenegger and Jason Statham have more avid followings, the film should put up big numbers. Lionsgate is distributing the film in North America. It comes courtesy of Millennium Films and Nu Image.

When the dust settles, the major story will likely be “Let’s Be Cops,” which got a jump on the weekend by premiering on Tuesday in 2,900 locations, before expanding to 3,093 on Friday. The R-rated comedy finds two friends (Damon Wayans Jr. and Jake Johnson) who don police costumes only to be mistaken for real law enforcement officials — a case of identity confusion that entangles them in a web of mobsters and corruption.

“It’s had a sleeper hit feel to it for awhile and the marketing has been hitting all the right notes,” said Shawn Robbins, assistant editor of BoxOffice.com.

The film cost a mere $17 million to produce and could gross $30 million in its first five days and $20 million to $23 million over the weekend. Twentieth Century Fox, which is backing the film, is being more conservative and pegging a five-day opening of $20 million to $25 million.

“Let’s Be Cops” finds a summer moviegoing audience eager to laugh again at our boys in blue, following the success of other recent cop comedies such as “Ride Along” and “22 Jump Street.” It continues 20th Century Fox’s hot summer, one that has included such hits as “The Fault in Our Stars” and “X-Men: Days of Future Past.”

The other major wide-release, “The Giver,” is also the biggest question mark. The Weinstein Company produced the adaptation of Lois Lowry’s summer reading list staple. It stars bright young things Brenton Thwaites and Odeya Rush, along with veterans Jeff Bridges and Meryl Streep.

Shot for an economical $20 million, the picture centers on a seemingly utopian society, one without conflict or sickness, that is gradually revealed to be built on a rocky foundation. It should pull in between $15 million to $17 million in its debut when it premieres on roughly 3,000 screens.

REVIEW: “Let’s Be Cops”

Lifting the overall box office are a pair of heavyweights. In its second week, “Teenage Mutant Ninja Turtles” should see its $64.5 million debut cut nearly in half, but will still likely be the weekend’s top grosser with more than $30 million. Then there’s “Guardians of the Galaxy.” The Marvel film continues to be a hit with fanboys and fangirls and should be able to reel in $20 million in its third week. For the new releases, the strength of these films could create a situation that is positively Darwinian.

“There’s going to be a traffic jam on the chart and a lot of movies are going to be bunched up together,” predicted Paul Dergarabedian, senior media analyst at Rentrak. “August is no slouch of a month.”

The good news for the industry as a whole is that after suffering through a box office downturn for much of the summer, an August rebound that kicked off with “Guardians of the Galaxy” and continued with “Ninja Turtles” should keep on trucking. The cavalcade of new releases should have no trouble trouncing the overall grosses of “Elysium,” “Planes,” “Percy Jackson and the Sea of Monsters” and “We’re the Millers,” all of which flooded the box office during the same weekend a year ago.