In short, if it’s a semi-automatic centre-fire it’s prohibited.
If it’s a shotgun, and the factory tube mag only holds 5 rounds, you are good. It’s time to take off the tube extension. If it takes box/removable mags – it’s prohibited.
If it’s a 22 and you only use 10 round magazines, its good.
Bolt, Lever actions, all good – but no mags over 10 rounds. But the BAR, SKS etc, all prohibited.
You will have six months from the time the buy back scheme is formalised to ‘surrender’ your firearm.
Stay legal, but, I would suggest you wait until details are formalised and you have an official deadline before doing anything. There are details emerging around the potential exemptions, and I imagine it will take a few months to get those clarified.
In the meantime, if a firearm is now deemed ‘prohibited’ – don’t take it out to shoot it. The police will likely take a dim view of that.
Stay safe, especially as the roar and duck season quickly approaching.