Once you have had a federal license (I maintained one for over fourteen years, buying buttfucking loads of guns and ammo for all my associates and massive quantities of ammunition to feed all those guns in our club - If there was really a problem with the USA FED, I would be one of those who go directly to jail, DO NOT PASS GO, etc ... etc ... etc...), you can still get just about anything, with proper licensing.
I have not bought a "gun" in a long time, but my last purchase was that of a Springfield, M14, heavy, with a Viet Nam era sniper barrel. It was perfectly legal, semi-automatic (the music says 3000meters of deadly accuracy, but I know the round well enough to know that, mostly, that is hype and bullshit. -- what's your target size? How much energy do you need downrange? --This range is over stated by at least one quarter. meh!) ... 7.62mm ... blah blah ... blah ... and I have it at my own home, not locked away, but in my media closet, at the top, well above my LPs.
Mostly, the investigations I have had to endure (back in the nineties, when I still kept perfect records of my exchanges - most of which went to police officers who had no other way of acquiring weaponry outside of normal chains of command and a "NEED" had to to be established in that realm, if they wanted to acquire a form of weaponry outside the normal duty rosters. There was no way, outside of siding with a hack like me for those guys, other than something outside the law. It was still perfectly legal to own anything in those days, except for rocket launchers and such.) came from curious federal inquisitions related to my (mid thirties era - John Dillinger style) Thompson sub machine gun and its associated hundred round .45 ACP drum magazine.
The fact is, I have a perfectly legal license to own a sub-machine gun (re-newed every year). The fact of owning the hundred round magazine seems to be more of a problem these days than the actual weapon is, which is licensed as fully automatic. I only own three automatic weapons, but for some reason this one is a NO-NO!!
.... if anyone stopped to think for a moment ... LoL!!
GAWD, where's teh Take-a-Shower smiley!