During a sting operation last year, he allegedly eyeballed three M-16 rifles, handguns with defaced serial numbers and a shotgun.
After showing the illegal firearms to two cronies, he drove the cache from a New Jersey warehouse, across the Verrazano Bridge and on to Long Island, the feds say.
For this shocking sellout of his badge, he received the not-so-princely sum of $6,000 - and his fellow cops got even less for the caper, court papers say.
The FBI made the guns inoperable before the sting, but Masso and his moonlighting miscreants didn't know that, officials said.
Police Commissioner Raymond Kelly speaks as U.S. Attorney Preet Bharara (l.) hosts a news conference at the U.S. Attorney's Office.
Mayor Bloomberg said the allegations were "deplorable" but didn't diminish the work of honest cops who have fought to get guns off the street.
Police Commissioner Raymond Kelly said he was most disturbed by the charge that Masso "actually saw what he must have certainly believed were functioning guns. It was a betrayal of the highest order of an officer's oath."
Masso, 47, and his lawbreaking lawmen shattered that oath over and over, also smuggling slot machines, cigarettes and clothing, the feds charge. They held clandestine meetings in hotel rooms and parking lots, filled car trunks with cases of illegal smokes, and broke into trucks, court papers say.
They did so at the behest of an FBI informant who was introduced to Masso while looking for someone to fix traffic tickets. A source said Masso's name surfaced on a wiretap in the summons scandal that has rocked the Police Department.
Masso was disciplined by the NYPD in 1998 for sending a letter to then-Manhattan Supreme Court Justice Leslie Crocker Snyder pleading for leniency in sentencing his cousin, Alphonse Malangone. A Genovese crime family soldier, Malangone faced up to 25 years and was sentenced to 15 years in prison for racketeering.
In this latest mark against him, the 18-year veteran told the informant he used to sell bootleg cigarettes from an Indian reservation and agreed to help him with similar schemes, court .papers say.
Masso, who worked the midnight tour at the 68th Precinct in Bay Ridge, recruited fellow cops and buddies to assist the informant and undercover agents posing as criminals, the feds say.
In secret recordings, Masso bragged about being a twisted headhunter, court papers say. "I'm getting a good army set up here," he said on one tape.
"You want a guy who beat the s--t out of somebody who bothers him. We got that. We got cops with vests and guns," he promised on another tape.
The 12 co-defendants - who face up to five years in prison on the top charge - were ordered freed on $100,000 bail each.
Masso, who has to wear an electronic monitoring device, will plead not guilty. "He's coming back and he's fighting the charges," lawyer Joe Mure said.
Those arrested with Masso Tuesday include 68th Precinct cops Eddie Goris and John Mahoney, Brooklyn South Task Force Officer Ali Oklu and 71st Precinct cop Gary Ortiz.
Also arrested were Joseph Trischitta and Marco Venezia, who were 68th cops while allegedly involved in the plots but have since retired, and Richard Melnik, also a retired cop.
Ex-sanitation cop Anthony Santiago, New Jersey correction officer David Kanwisher and Santiago pals Michael Gee and Eric Gomer were also busted.
Four more officers named in the complaint but not charged have been placed on modified duty pending an NYPD probe.
The informant was an illegal immigrant who received money and help staying in the U.S. in exchange for his work with the FBI. He introduced Masso and others to undercover agents who were posing as criminals.
None of the items transported across state lines were actually stolen, but transcripts of secret recordings show the defendants were told they were.
In one episode last May, members of the group allegedly went to Virginia to break into tractor-trailers outside a warehouse.
They bought bolt cutters, snipped the locks and made off with 200-plus cases of cigarettes worth $500,000.
Masso's team got $92,000 for that job, the feds say. All told, they allegedly pocketed more than $170,000 - though Masso whined they were underpaid.
"They're risking a lot for a little," he said at one point.
At the cops' homes, relatives and neighbors expressed disbelief. Ortiz'relatives in Brighton Beach said the charges must be a misunderstanding.
"He loves being a cop," said Tommy Rodenzo, 19, who dates the cop's niece. "He says there is no better reward than to help people."