A Border Force expert estimates there could be thousands of AK-47s in Australia after two of the high-powered assault rifles were allegedly found in the possession of Melbourne teenagers.

Former Border Force Commissioner Roman Quaedvlieg said he’s not surprised the Russian-designed AK-47 weapons were being found in Melbourne.

An 18-year-old man has been charged with possessing a firearm. Credit:Victoria Police

He said many were housed with collectors.

“They were originally built in the Soviet Union in the late '40s. Over time there’s been about 100 million or so manufactured in the global market. In the '50s and '60s it was quite easy to get them into the country,” Mr Quaedvlieg told 3AW.