Technically only the M16A3 was fully automatic, and it's use was discontinued by the military, they now use the M16A4 and the M4
And law enforcement wouldn't be using the A3 either, they would also use the M4.
I am just curious where the hell the A3 came from since most M16 models are now semi/burst fire only.

And further more, how come there is only one model of pistol (that I have seen)
Where are the revolvers, the Magnums, the Desert Eagles, the Glocks and the Colts?
And no (apparent) Tactical Sniper Rifles either? If there are M16's just lying around, then there should be a few Law Enforcement grade sniper rifles too.
And no MP5s? Those are much more common in law enforcement then (cough) the M16A3.
Then again, magical Unicorns are more common with the police/Swat etc, than M16A3s.
And what about civilian weapons? There aren't just the same 4 or 5 types of weapons over and over again. Hell, the civilian population has a greater variety of firearms than our military