Kane Dalrymple, 32, and Corey Moore, 49, pleaded guilty to firearms charges in the County Court on Friday, after selling two guns to Yacqub Khayre.

Khayre, who claimed to represent Islamic State, was killed in a shoot-out with police after the June 2017 siege.

It's accepted neither man knew what Khayre planned to use the guns for but Judge Carolene Gwynn said they must have known he would use them in a "nefarious fashion".

The two men met Khayre at his house in the early hours of April 14, 2017, to pass the weapons, including a Barton 12-gauge shotgun, over the fence to Khayre.

Dalrymple had known the hostage-taker since childhood and acted as a middle man between Khayre and Moore.

Coded messages between the old friends discussed the exchange of a "six-seater" and a "bicycle pump", references to a six-round capacity gun and and a pump-action weapon.

In another message a "full tank" was discussed, in reference to ammunition.

It was suggested on the night Dalyrmple might drive but he was not licensed and they decided to get at taxi because there were "too many 5-0" or police around.

The exchange happened at Khayre's house. He was on strict parole at the time and had to obey a curfew and wear an electronic monitoring bracelet.

Dalrymple and Moore were arrested days after the siege, when the younger man told police the coded messages he exchanged with Khayre were references to drugs.

His barrister Wayne Toohey said Dalrymple was still in shock the "dreadful" attack had happened and to distance himself from it was "human nature".

Judge Gwynn made it clear the two men would not be punished for Khayre's actions but said their crimes were serious.

"(They) must have had some belief they were to be used in some nefarious fashion," she said of the guns.

Judge Gwynn bailed the 32-year-old on Friday, concerned he might serve longer than the minimum sentence she will hand down on July 5.

But she warned if he put one foot wrong he'd be back in jail and she'd be rethinking his rehabilitation prospects.

Dalrymple spent 18 months in prison awaiting trial on these charges before pleading guilty on Friday.

Mr Toohey said time served and a community corrections order would be sufficient.

Moore, who has been on bail, will return to prison when he's sentenced.

His lawyer Barnaby Johnston said Moore had done more than 150 hours of volunteer work while free.

"He has done more than focus on his own recovery. He has focused on the recovery of others," Judge Gwynn acknowledged.

She was reluctant to send him back to prison but his crimes required a longer sentence than the time he served on remand previously, the judge said.

Australian Associated Press