In the early '80's I was stationed at Holsworthy Army base (near Sydney Australia) and there were limited times/dates we could do live firing with our M2 .50 Brownings. The reason given was that richocets were a danger to civilian aircraft flying into and out of Kingsford Smith on certain flight paths.

No doubt the paper ballistics produced a danger and anecdotal gossip was that an incident, without fatality had occured in the past.

No doubt something like this will be used to justify the ban as well as the threat of divisive elements getting their hands on weapons capable of long range material disruption.