So I did some digging tonight and managed to locate the exact legislation around how much powder we can store for reloading. In NSW we can keep 12Kg legally as per the current legislation.
Explosive Regulation 2013, Part , Division 4, section 48 , Item 2(C)
48 Ammunition
(1) A person who is a licensed firearms dealer under the Firearms Act 1996 is not required to be authorised by a licence in order to possess, store, transport, sell or supply:
(a) ammunition, or
(b) percussion caps, or
(c) not more than 12 kg of propellant powder.
(2) A person who holds a licence or a permit under the Firearms Act 1996 (other than a firearms collector licence) that authorises the person to possess or use a firearm is not required to be authorised by a licence in order to possess, use, store or transport:
(a) ammunition, or
(b) percussion caps, or
(c) not more than 12 kg of propellant powder.
(3) A person who holds an ammunition collection permit under the Firearms Act 1996 is not required to be authorised by a licence in order to possess or store ammunition that is authorised to be possessed under the permit.
http://www.legislation.nsw.gov.au/viewtop/inforce/subordleg+476+2013+cd+0+N/?autoquery=(Content%3D((%22propellant%22)))%20AND%20((Type%3D%22act%22%20AND%20Repealed%3D%22N%22)%20OR%20(Type%3D%22subordleg%22%20AND%20Repealed%3D%22N%22))%20AND%20(%22Historical%20Document%22%3D%220%22)&dq=Document%20Types%3D%22%3Cspan%20class%3D%22dq%22%3EActs%3C%2Fspan%3E,%20%3Cspan%20class%3D%22dq%22%3ERegs%3C%2Fspan%3E%22,%20Search%20In%3D%22%3Cspan%20class%3D%22dq%22%3EText%3C%2Fspan%3E%22,%20Any%20Words%3D%22%3Cspan%20class%3D%22dq%22%3Epropellant%3C%2Fspan%3E%22&fullquery=(((%22propellant%22)))