A defence expert is backing the government's move to keep track of who owns what firearm.

The government has announced the second tranche of gun law changes which includes a gun registry and tighter licensing rules.

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Massey University Defence and Security Studies Centre teaching fellow and doctor John Battersby told Kate Hawkesby it's important knowing how many firearms are out there , and who's got them.

But he says for the register to work, it's got to get enough funding.

“Most of the changes only impact law-abiding citizens. The focus needs to be on addressing people getting their hands on illegal weapons.”