William McMullan, 66, of Loughdoo Road in Newtownards, was arrested by National Crime Agency officers at his home address in November 2019.
The NCA were alerted after Border Force officers at Coventry International Postal Hub detected parts of the automatic weapon, along with parts of a revolver and a self-loading pistol in two separate packages.
Following his arrest McMullan admitted buying the weapons while he was on holiday in the US, and mailing them back to his address in Northern Ireland.
McMullan appeared before Downpatrick Crown Court on Thursday 12 September where he pleaded guilty to firearms importation offences.
On Friday 20 September, at the same court, he was sentenced to 10 months in prison, suspended for 12 months.
NCA Belfast Branch Commander David Cunningham said: “These firearms could have caused mass casualties in the wrong hands. The AR-15 in particular is a military-style rifle, of the type known to have been used in a number of high profile mass-shootings in the United States. There is no place for deadly weapons like these in Northern Ireland.
“These were serious offences, and McMullan was foolish in the extreme to think he could get away with it.
“We work closely with our colleagues at Border Force to protect the public by preventing illegal firearms reaching our streets.”
Phillip Holliday, Regional Director of Border Force Central said: “Border Force are committed to stopping firearms from entering the country illegally, where they fuel organised criminal gangs and ruin lives.
“We will continue to work tirelessly to keep the public safe and our borders secure.”
More news from Belfast
