An Adelaide gunsmith has attracted controversy after his decision to legally modify a shotgun to match the ammunition load of a higher capacity version which was banned from importation last year.

Key points: The importation of eight-shot Adler guns was banned for 12 months last August

The importation of eight-shot Adler guns was banned for 12 months last August Modification of the five-shot gun to make it an eight-shot gun is legal in all states apart from NSW

Modification of the five-shot gun to make it an eight-shot gun is legal in all states apart from NSW Modification is a simple process and can be done in as little as 10 minutes

Importation of the eight-shot Adler lever action shotgun was suspended for 12 months in July because it could fire up to eight shells before needing to be reloaded.

Nik Halliwell runs a gun modification workshop in the Adelaide suburbs and is one of the few people in Australia able — and willing — to legally modify existing five-shot Adlers to give them a magazine capacity of eight or 11 cartridges.

The eight-shot Adler has infuriated Australia's gun control lobby, who believe it is an attempt to undermine the 1996 National Firearms Agreement brokered by John Howard following the Port Arthur massacre.

Gun Control Australia spokesman Roland Browne said the guns were completely contrary to the spirit of the national agreement.

"They just didn't exist in 1996, they exist now," he said.

"They undermine the agreement and they put the entire public's safety at risk."

However, NSW Upper House member Robert Brown, who is a member of Australia's most powerful pro-gun political group, the Shooters, Fishers and Farmers Party, said he was not concerned.

"Who cares? We don't want the '96 agreement," he told 7.30.

"The '96 agreement … was a piece of garbage — it should be torn up.

"The states had, in 1996, very strict firearms laws.

"Yeah, it went very bad in Tasmania, but every state then had the capacity to do what they thought they needed to do."

Do-it-yourself guides available

Sorry, this video has expired Nik Halliwell shows how to modify a legal Adler to make it a 7 or 11 shot gun.

Mr Halliwell said modifying the gun took him 10 minutes and he had also emailed three-page do-it-yourself guides to people who "knew their guns".

He said gun owners who used more powerful guns, in the heavily restricted categories C and D, were switching to the Adler, which is in the less restricted category A.

"A lot the professional shooters, C and D class, that I work with who run, say a pump action C class shotgun, they're actually converting to these as a category A because they can have more shots," he said.

"So if they're culling from helicopters or chasing down pigs and dogs, it makes them easier to get repeated shots."

Do you know more about this story? Email 7.30syd@your.abc.net.au

While the Federal Government has temporarily banned importation of the eight-shot Adler, most states have no restriction on how many rounds owners can have in their lever action shotguns, which means it is legal to modify the five-round Adler.

Mr Halliwell's work has been criticised because of the import ban and has come to attention of law enforcement agencies in other states and politicians opposed to the gun.

Greens senator Nick McKim want the ban on the 7 shot Adler shotgun to be made permanent

Greens senator Nick McKim said the intent of the 12-month ban was very clear.

"We now understand that people are working around that by engaging in modifications of magazines to allow for more shots than is currently covered in the import ban and we would like to see a lot of these loopholes cleared up," he said.

The Shooters, Fishers and Farmers Party disagrees.

"If it's legal in South Australia and he's not prosecuted, I can say to you that it doesn't really matter from a public safety point of view how many rounds they can change the magazine over (to)," Mr Brown said.

The controversy is set continue for at least a few more months, with concerns the importation ban, due to expire in August, will lapse before the Government has made a final decision about what to do with the Adler.