Federal Law only limits the sale and possession of items listed in the National Firearms Act. These items include:
Machine guns - any firearm that can fire more than one round per trigger pull which includes "burst fire" (i.e. 3-round burst)
Short-barreled rifles - any rifle with a barrel length under 16" or an overall firearm length under 26" (that's measured with the folding/collapsing stock in the extended position)
Short-barreled shotguns - any shotgun with a barrel length under 18" or an overall length under 26" (just like the rifles)
Silencers - any portable device designed to muffle or supress the report of a firearm
Destructive devices - This has two broad classes:
-(a) - Devices such as grenades, bombs, explosive missiles, poison gas weapons, etc.
-(b) - Any firearm with a bore over 0.50 inches except shotguns which have been deemed suitable for "legitimate sporting use"
Any Other Weapons - This is a broad catch-all that is used by the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) to enforce registration and taxation. These include (there are others, but these are easiest to describe):
(1) Smooth-bore pistols
(2) Pen guns and cane guns
(3) Disguised firearms
(4) Firearms that can be fired from within a wallet holster or briefcase
(5) Handguns with a forward vertical grip
State-laws vary (naturally) from state to state. In addition, cities within each state can enact their own ordinances limiting where people can carry a firearm.
For instance, many places in Arizona have an open-carry policy, where you can wear a gun on your hip in plain sight without a need for any type of permit.
Where I live in San Antonio, you must obtain a concealed carry permit to legally carry your handgun (concealed) where it is legally allowed to do so. However, businesses retain the right to forbid concealed weapons on their premises. It is also against city ordinance (and I believe State law, but I'm not sure on this) to have a concealed firearm in a public building (courthouse, police station, etc.) even if you have a concealed carry permit.
You do not, however, need a permit of any sort to keep a firearm in your house or vehicle under the State's "Castle Doctrine."
As far as obtaining any of these things, under Texas law, it's fairly straight-forward. I can, as a Texas citizen own any of the things I have mentioned above, even a machine gun. However, in order to purchase a machine gun, the BATFE requires I get a signature from the Bexar County Sheriff (the county in which I reside), which the Sheriff no longer does, as far as I'm aware. No law was enacted, the Sheriff just straight up decided he (or she) was no longer going to grant permission for new applicants. I do believe, however, that they will still grant suppressor applications, assuming the applicant passes the necessary background checks.
And every firearm I have purchased required a background check through the FBI. One handgun I purchased at Bass Pro, the other I purchased at the local gun show. Both times, from the time I selected the handgun I wanted, to the time the transaction was completed, took roughly 30-45 minutes. I suspect the same would be true for any semi-automatic rifle that is not restricted by the NFA restrictions above.
When it comes to the definition of "assault rifle," that all depends on what the state you live in defines it as. While I may define an assault rifle as any rifle that's fully automatic, that may not always be how your particular state's laws define it.
The federal level does not have a definition for "assault rifle" anymore since the Assault Weapons Ban of 1994 expired. However, under that 1994 ban, an assault weapon was classified, for the most part, as any semi-automatic firearm that merely
looked like its fully automatic counterpart.
TL: DR?
