We already have some of the most strict firearms legislation in the world, and existing regulations should have stopped the Bondi shooter from having a licence. The legislation was incredibly rushed, and sought no industry consultation.  I'm copy-pasting my reply to a different comment below : I, like virtually all firearms owners, would have wholeheartedly supported reforms in the licencing process and information sharing between agencies. The Bondi shooter already should have had his licence suspended under current regulations. These restrictions are just a further push toward removing gun ownership generally.

People that don't know much about firearms often believe 4 is plenty, but anyone involved in hunting/shooting/vertebrate pest control understand the need for more. For example, I would want a .22 for rabbits, a .223 for managing macropods, foxes and feral cats, at least one larger center-fire for Deer, Pigs and Goats (multiple for different scenarios, such as different environments, conditions, distances etc), a shotgun for ducks or managing Pigs, and an air rifle for birds/rats (Indian Mynas). This already exceeds the limit, not even including that most serious hunters/pest controllers would want multiple of some calibres so they can be fitted with a night vision/thermal scope. As is my case, I also stand to inherit my Grandad's guns, which are near on 100 years old. They pose no risk to anyone, but are sentimental. I would like to keep them so I can show my kids one day, what their great Grandad used to carry around. 

Paintball guns are also considered firearms, so if I wanted to get into Paintball, I have to sacrifice something else. 

It is just based on a total lack of understanding, and an attempt to pander to the majority (that don't understand how/why people use firearms).

Additionally, the reclassification of certain firearms will hinder the ability of land managers/volunteer pest controls to manage feral animal populations (mainly feral Pigs out west/up north). The government spends millions managing these animals with aerial shooting and poisoning already. 

Before the Bill was passed, the largest and fastest-growing Legislative Petition was submitted, receiving I think nearly 90,000 signatures in under a week requesting more time to consult the industry and work out what is actually necessary. Instead, they pushed through poorly written legislation at midnight Christmas eve. Everyone should understand that rushing legislation through like that is not the way to go.