The father-of-two said he had returned home to the farm he manages about 20km out of Ashburton for lunch on May 13, when "seven or eight" police cars sped up his driveway and blocked potential exits.
Then 14 police officers, more than half of whom were armed with semi-automatic rifles and side-arms, left the vehicles and spread out across his front yard, before two plain-clothes detectives came to his front door to chat, he said.
"Fortunately our two young children [5 and 11] were at school at the time, but you can imagine how traumatic it would have been if they'd been playing out front when all these armed police turn up," Mielnik said at the time.
The detectives began by explaining the reason for the raid was Mielnik's purchase of an AR-15 semi-automatic rifle from Gun City, the day after the Christchurch terror attacks in March.
His rifle was then confiscated. Mielnik said he understood the reasoning behind the rifle ban and seizure, but not why he was targeted in such a heavy-handed manner.
A separate Christchurch man had earlier spoken to media about a raid on his home in which he claimed a rifle was levelled at his 12-year-old daughter.
Police were now sending an assistant commissioner to Christchurch to meet with concerned firearm owners and their lawyers.
Deputy Commissioner Mike Clement last week said he was confident the raids had been conducted in a professional manner and that no weapons had been pointed at children.