Former New York mayor Michael Bloomberg, who is spending US$50 million against the powerful US gun lobby, was the target on Friday of an angry NRA, which hailed firearm freedoms at its annual convention.
"Mr Bloomberg, you're an arrogant hypocrite," Chris Cox, who heads the National Rifle Association's lobbying arm, told a crowd of gun enthusiasts who booed upon hearing the former mayor's name.
Being a billionaire "does not entitle you to tell us how to live our lives", Cox added about Bloomberg, who did not attend the association's annual meeting and exhibit in Indianapolis.
"Stay out of our homes, stay out of our refrigerators, and stay the hell out of our gun cabinets, because this freedom is not for sale."
Along with the US government and media, the NRA has made Bloomberg one of its prime political targets, with his name denigrated on conservative talk radio and on large posters at the convention.
NRA head Wayne LaPierre unveiled an anti-Bloomberg video slamming the politician as an elitist fighting to restrict gun rights.
"This guy thinks he can scare us into running from a fight to protect our rights and our freedoms," a man says in the clip. "He's one guy with millions. We're millions with our 25 bucks. Let's see who crushes whom."
Hundreds of exhibitors descended on a convention centre here to display thousands of semi-automatic handguns and military-style rifles for sale in the US market.
Several potential Republican presidential candidates courted gun-rights supporters at the National Rifle Association's annual convention, talking up their pro-gun credentials.
US Senator Marco Rubio of Florida, former Pennsylvania US Senator Rick Santorum, Indiana Governor Mike Pence and Louisiana Governor Bobby Jindal addressed the forum.
Wisconsin Governor Scott Walker and Senators Ted Cruz of Texas and Kelly Ayotte of New Hampshire also recorded brief videos that were played for the crowd of more than 2,000 inside Lucas Oil Stadium, home to the Indianapolis Colts.
Additional reporting by Associated Press