It’s a feeling based idea to assuage the public rather than a logic based one. If someone has four guns already there is little difference between what damage they are likely to be able to cause with those four vs what they could do with five, six, or seven (and the difference is less significant again if they already have ten). The limits seem rather arbitrary instead of evidence based and would not stop a repetition of the Bondi massacre, they appear instead to just be a quick decision made to show the government is doing something in reaction to a tragedy (something must be done, this is something therefore we must do it…).