I understand and agree regarding "unregistered handgun". This has been an ubiquitous term used just as much in areas where there is no registration as in areas where there is. I suppose because most MSM reporters come from big cities and states where there is registration, they simply assume registration is the norm. As does Hollywood in most every crime drama they make.
The OP was because "unregistered ammunition" is a term I haven't heard until the last year or so. I can't help but think "propaganda" given all the other crap going on right now to silence, restrict, and ban.
And as Castle Key posted, it appears to be a real thing in DC.