US President Barack Obama has again pointed to Australia's swiftly introduced, post-Port Arthur massacre gun laws as an example for America.

Mourning last week's gunning down of nine churchgoers in Charleston, South Carolina, and frustrated by a Congress he describes as in the lobbying grip of the National Rifle Association, the president said the US public needs to be more vocal.

He doesn't expect "real" action on gun laws.

"When Australia had a mass killing, I think it was in Tasmania about 25 years ago, it was just so shocking to the system, the entire country said, 'We're going to completely change our gun laws'," said Obama, during a podcast interview with Los Angeles comedian Marc Maron.

"They did and it hasn't happened since."

In 1996 28-year-old Martin Bryant killed 35 people at the historic Port Arthur tourist site in Tasmania and soon after Prime Minister John Howard led the introduction of strict gun laws in Australia.

A year ago Obama also publicly pointed to Australia as an example after, in the space of a few days, a student was shot dead at an Oregon high school and a couple went on a shooting rampage in Las Vegas that left two policemen and a Wal-Mart shopper dead.

After 20-year-old Adam Lanza shot 20 children and six adult staff dead at Connecticut's Sandy Hook Elementary School in 2012 Obama attempted to introduce expanded background checks for gun purchases, but it was blocked by Congress.

Another attempt to ban semi-automatic weapons was also beaten.

Since the Sandy Hook massacre it has become easier to carry guns in public in some US states.

Obama said gun manufacturers "make out like bandits" after each massacre with spikes in gun and ammunition sales because of fear the government would take Americans' guns.

New laws need to respect the traditions of gun ownership in the US, he added.

"The question is just, 'Is there a way of accommodating that legitimate set of traditions with some commonsense stuff that prevents a 21-year-old who is angry about something or confused about something, or is racist, or is deranged, from going into a gun store and suddenly is packing and can do enormous harm?'" Obama asked.

"It is not something we have fully come to terms with.

"Unfortunately the grip of the NRA on Congress is extremely strong.

"I don't foresee any legislative action being taken in this Congress and I don't foresee any real action being taken until the American public feels a sufficient sense of urgency and say to themselves, 'This is not normal. This is something we can change and we're going to change it'.

"If you don't have that kind of public and voter pressure, then it's not going to change from the inside."