Gun control advocates have called for the resignation of federal Justice Minister Michael Keenan over a 'do it yourself' magazine extension kit that has emerged since thousands of rapid-fire shotguns flooded into the country.

More than 7000 Adler 110 shotguns have been imported by sidestepping a temporary import ban introduced by Tony Abbott in July, sparking a DIY magazine extension market, Gun Control Australia claims.

"We are seeing a nightmare unfold before our very eyes and years of strong gun laws being undermined by this one decision," chair Sam Lee said in a statement on Monday.

"A new do-it-yourself magazine extension market has recently emerged."

While the ban halted imports of a version of the Adler that could shoot eight rounds without the need to reload, a modified version firing five shots in rapid succession was soon introduced.

The extensions legally convert the five-shot version of the Adler so it can hold up to 11 rounds.

Mr Lee has called for Mr Keenan to step down after AAP revealed the Australian Crime Commission warned the government that gunsmiths and owners would convert the guns.

The advice was contained in a submission dated July 21 from ACC CEO Chris Dawson, according to documents released by the Attorney-General's Department under freedom of information laws.

The warning to Mr Keenan said "the manufacture of an after-market extended magazine is not difficult and requires no specialist gun-smithing skills".

It was listed under the heading: "Expected Reaction".

A spokeswoman for Mr Keenan has previously told AAP it was "wrong" to suggest the minister didn't follow the advice of law enforcement agencies.

"The minister receives ongoing advice from agencies regarding firearms. Such advice led to the importation ban on certain lever action firearms," she said.