Former New York mayor Michael Bloomberg, who is spending $US50 million ($A54m) against the powerful US gun lobby, has been the target of an angry National Rifle Association, which hailed firearm freedoms at its annual convention.
"Mr Bloomberg, you're an arrogant hypocrite," Chris Cox, who heads the NRA's lobbying arm, on Friday 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.
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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 who."
LaPierre said one way to counter Bloomberg was for NRA members to to elect lawmakers who support Second Amendment rights, the part of the US Constitution that protects the rights of the individual to keep and bear arms.
"The NRA will not go quietly into the night," LaPierre said, adding that Bloomberg aimed to "spend $50m to beat us in November."
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.
The NRA is the US's largest pro-gun organisation, claiming one million members, and the event drew several Republican politicians that are considered possible presidential candidates in 2016, including Senator Marco Rubio and Louisiana Governor Bobby Jindal.
Bloomberg announced in April that he would spend millions of his personal fortune to help reduce gun violence across the US, in part by launching an initiative that backs candidates who advocate firearms control.
The creation of his "Everytown for Gun Safety" group came after Congress failed to pass a hotly-contested gun-control law last year, despite a series of mass shootings that shocked the nation.
