The commander of the NSW Police Force armoury has defended the type of assault rifles and ammunition used by tactical police when they stormed the Lindt cafe in Sydney.

Each Tactical Operations officer who stormed the cafe in the final moments of the siege was armed with a M4 carbine assault rifle that fired .223 calibre pointed soft-point rounds.

Appearing before the siege inquest, Inspector Richard Steinborn rejected a suggestion the .223 calibre round was unsuitable for hostage recovery situations.

He also rejected suggestions that bonded bullets, like those used by the Australian Federal Police, or lower velocity 9mm rounds used in police-issue Glock pistols, would be safer.

"No ammunition is designed to be safe, ammunition is designed to inflict injury," he said.

"Any round fired into a confined area presents risk."

"The .223 round we use is designed to penetrate no less than 12 inches [into the target] and no more than 18 inches, and it does that."

Inspector Steinborn conceded that .223 rounds had a higher risk of fragmenting but said bonded bullets, which are designed to penetrate barriers such as plasterboard walls or vehicles, have a higher risk of over-penetrating the target and killing or injuring nearby hostages.

"[A bonded round] would potentially still have small fragments," he said.

"But you would have a very large projectile travelling at more than 1000 feet per second ... presenting a ricochet risk in the stronghold."

Shortly after the siege, former member of the 2nd Commando Tactical Assault Group Mitchell McAlister publicly questioned the choice of weapon used by police during the incident in an article written for an American online journal.

Mr McAlister noted that the M4 carbines fire heavy 5.56mm rounds that would have "dangerous effects in a sense and enclosed environment" such as the marble interior of the Lindt Cafe.

Weapon useful in a variety of situations

Inspector Steinborn also told the inquest the NSW Police Force adopted the use of .223 rounds in M4 carbine assault rifles in the mid-1990s and it was the weapon of choice for the Tactical Operations Unit because it could be used in a variety of situations and ranges.

Two hostages died when Man Monis held hostages during a siege at a Sydney cafe. ( Sergio Dionisio: AAP Image )

"It's the standard weapon that is used by all police tactical groups in Australia," he told the inquest.

"It can be used by officers who are outside a stronghold.

"It can be used by the entry team because it is a shorter length than the standard military-type rifle it is derived from.

"All of our testing with our current rounds shows it performs appropriately and consistently."

Hostage Katrina Dawson was killed when she was struck by a number of bullet fragments when tactical police forced entry to the Lindt Cafe.

The inquest has previously heard that the police sniper who saw gunman Man Haron Monis inside the Lindt Cafe could have shot him.

It has also previously heard that police had agreed to let Monis speak on ABC radio in exchange for the safe release of hostages, but negotiators decided it was too dangerous to grant the request.

The inquest continues.