The indictment alleges that former officer Danny Harris Jr., of Pinole, bought three semiautomatic pistols from an unidentified gun dealer in San Jose in June, July and November 2009 on behalf of two minors and one other person.
Harris is charged with four counts of making false statements on federal firearms transaction forms about the true buyers of the guns.
In addition, he and fellow former officer Raymond Thomas Jr., of Fairfield, are each charged with one count of conspiring to prevent disclosure of the alleged crimes to federal law enforcement officers and one count of obstructing a grand jury investigation.
The indictment alleges the two men's schemes to deceive authorities included hiring a private investigator in Concord to conduct a sting operation in which the two youths were to be arrested for drunk driving and illegal possession of the pistols.
A second plot was to have a woman who worked for the investigator set up a date with one of the youths and ask him to bring his gun to their meeting, the indictment alleges.
The document does not give the name of the private investigator.
The two men are due to make an initial appearance before a federal magistrate in Oakland on Aug. 9.
The charges each carry maximum sentences ranging from five to 20 years in prison, if the defendants are convicted.
U.S. Attorney Melinda Haag said the prosecution results from an 11-month investigation by the FBI, the Richmond Police Department and the Contra Costa County District Attorney's Office.