Martin Place siege inquest to examine Monis shotgun

Ballistics experts will give evidence about the shotgun used by Man Haron Monis when the inquest into Sydney's Lindt Cafe siege resumes today.

Police firearms experts will reveal what has been discovered about the sawn-off, pump-action weapon.

Previous evidence to the inquest revealed the gun had not been registered and is believed to be one of an estimated 250,000 "grey market" unregistered weapons in Australia.

The shotgun should have been handed in during the compulsory buyback of semi-automatic weapons introduced in 1996 following the Port Arthur massacre.

Counsel assisting the inquest Jeremy Gormly SC has told the court police are still investigating how Monis came in possession of the gun.