During the secret meetings at their clubhouse in Brooklyn, the members of an outlaw motorcycle gang, the Forbidden Ones, secured themselves with assault rifles, pistols and even grenades to protect themselves from intruders, the authorities said. But their first — and most imposing — line of defense was a cannon, at the ready with .50-caliber rounds, aimed at the door should anyone dare to infiltrate their ranks. Enlarge This Image Department of Justice Among the weapons confiscated were AK-47 assault rifles, homemade bombs, pistols and a cannon. Connect with NYTMetro Follow us on Twitter and like us on Facebook for news and conversation. But what the men did not know was that despite their fortifications, one of their own had turned on them. Their very own “enforcer,” responsible for ensuring that they were all well armed with guns and explosives, was a confidential informer working with New York police officers and federal agents to uncover the sale of a huge cache of weapons. In predawn raids on Tuesday, law enforcement officials arrested seven members of the Forbidden Ones and two other Brooklyn-based motorcycle gangs, the Dirty Ones and the Troublemakers, and charged them with trafficking high-caliber weapons. An eighth man charged was already in prison. Among those discovered, in 15 locations, were AK-47 assault rifles, homemade bombs and a .410-caliber revolver, the police said. Some of the guns were kept at a gang member’s home, where his wife ran a day care center. The men arrested had nicknames like Spider and Afro, and some literally wore their accomplishments on their sleeves. The “1% patch” they wore declared that they had rejected society and lived outside the law. And the “bangout patch,” showing two handguns crossing each other, signified that the member had assaulted or had another confrontation with the police. Most of the gun sales were made in tattoo parlors, the police said. The defendants, ranging in age from 33 to 61, were scheduled to be arraigned in Federal District Court in Brooklyn on Tuesday afternoon, but only three made court appearances. Four others were taken to the hospital for heroin detoxification and treatment for high blood pressure. The men face up to five years in prison if convicted. Officials said the leader of the trafficking scheme was Scott Brannigan, known as the Spider. Prosecutors said Mr. Brannigan, 61, sold 16 firearms and about 1,400 rounds of ammunition, including armor-piercing rounds, to an undercover officer. The most expensive of the arms, at $2,000, was the cannon, which came with ammunition and the black powder necessary to fire it. The first undercover gun buy was in October 2010. The confidential informer led an undercover officer to a tattoo parlor on Rockaway Beach Boulevard in Queens. At a nearby house, the informer paid $1,000 for a Yugoslavian assault rifle and ammunition, while the undercover officer looked on. It went on like that, the police said, for the next two years.