Key Points:

Guns from a missing Coromandel collection have fallen into the wrong hands and created a black market legacy that will last for decades, say police and a gun control advocate.

One of the guns among Hot Water Beach collector John Mabey's missing pistols, submachine guns and semi-automatic rifles has been identified as the weapon used in a fatal shooting.

Mabey's guns disappeared in July last year, and police say eight of the 10 that have been recovered were found in the hands of gang members and people involved with illicit drugs.

Mabey says 121 guns were stolen from his home, but has pleaded guilty to charges of illegally selling or supplying 30 restricted weapons.

Police say it is inevitable more of the missing firearms will surface in criminal hands.

Gun control advocate Philip Alpers says they have "armed New Zealand gangs for decades to come".

"It's like gravity," he said. "These weapons always dribble down to the people we least want to have them."

Fourteen months ago, a wanted man was captured with two of Mabey's pistols - Beretta and Glock semi-automatics - after firing at police during a car chase in Auckland.

Others have been recovered in raids on gang premises, and in the latest incident, forensic tests showed a .22 calibre pistol belonging to the missing collection killed Whangamata man Nigel Lurman in September.

Police said at the time that he had been with three friends and they were using recreational drugs.

The pistol was recovered during raids on Whangamata properties on November 20 in which cannabis and methamphetamine were also found.

Detective Sergeant Glenn Tinsley, one of the officers in charge of the investigation into Mabey's missing

collection, said it was alarming his guns had now been used in a fatal shooting as well as against police.

Mabey is to be sentenced this month in relation to 30 of his missing guns, after he admitted keeping those guns in an operable condition.

This contravened the condition of his collector's licence, which required certain guns be kept disabled.

Police believe most of his missing collection was in working order - a prospect which Mr Alpers, who runs, said was "very unsettling".

"Given the longevity of firearms and the character of the people they've been leaked to, Mabey's guns are almost certain to injure more people."

In the past, criminals had armed themselves with sawn-off shotguns and rifles, but Glock and Beretta pistols - "purpose-built to kill" - had become the new weapons of choice.

The police national manager of licensing and vetting, Inspector Joe Green, disagreed, saying there was no evidence pistols were becoming more prevalent in crimes.

He said cases like Mabey's were rare in a country with 214,000 firearms licence holders and up to 1.2 million firearms, and current legislation allowed those who broke the law to be dealt with appropriately.

Mabey's missing collection:
Includes 113 pistols, five submachine guns and three military-style semi-automatic rifles.

Guns recovered: 10
Eight found in possession of gangs and criminal fraternity, one found without an owner, and one handed in to police.