In the film, which was directed by Icelandic director Baltasar Kormakur, who directed the surprise hit thriller from last year, Contraband (a remake of his 2008 film Reykjavik-Rotterdam), deals with a DEA agent and an underground Naval Intelligence officer who are investigating each other and steal mob money for the their respective agencies. However they get in deep water when they realize that a cache of $50 million stolen by them from the mob, actually belongs to the CIA
Starring along with Washington is Contraband star Mark Wahlberg, as well as Edward James Olmos, Bill Paxton and (OH NO!) Paula Patton.
From the description, 2 Guns is evidently like Safe House. Not a personal project on which everyone took a huge pay-cut to get it made, like Flight, but another "big paycheck" role for Washington.
But hey, who's complaining? He's one of the very few Hollywood stars left who can still demand a huge paycheck and get it.