So really what you are saying is you are just working on a “hunch” We know that it didn’t have effect on “normal” gun crime due to several studies that are newer than your cite.
As for the mass killings I am very very happy Australia hasn’t suffered any in a while and that is great news but to claim it was all even part due to the NFA is just not acceptable as a debate point without some form of cite.
Unfortunatly we have a much worse problem with gangs and murder here in the US but if you avoid violent felons and don’t sell or buy drugs your risk of murder is tiny.
I would appricate any cite that shows any correlation between the number of legal firearms owned and the murder rate or spree murder rate.