He is positive people will turn in their prohibited firearms but acknowledges that the total number of prohibited firearms is not known.
"You're not going to have people keep these guns when they face not only losing their license and their guns, but five years in jail."
But Council of Licensed Firearms Owners spokesperson Nicole McKee said the buy back has been a failure.
She believes there were 170,000 prohibited guns in New Zealand and that "50,000 is not a number to boast about".
McKee said they have always told people to obey the law but that people have floated three reasons to not turn in their weapons.
"Some of them are going to hide their firearms, some of them are protecting history, and some of them - a good portion of them - don't know what's going on," she said.