Okay...I don't have my list in front of me, so if I leave anything out, correct me.
A rifle is an "assualt rifle" (Dumbest bit of lingo ever heard...All rifles are made for assualt...thanks Hitler...) if it has more than
two of the following features:
1. A pistol grip.
2. Detachable magazine.
3. Bayonet lug/mount (Gotta worry about those drive-by bayonetings!)
4. Flash suppressor
5. Collapsible stock
A rifle made before the law was passed (1994) is considered "Pre-ban" and is still legal to be owned and used in most states (We're dealing with a federal law...Certain areas may be more strict). It is even legal to purchase parts for these weapons in order to repair them (i.e., I could order a collapsible stock from Bushmaster to put on my pre-ban rifle). However, I need to be able to prove that the rifle was put together before the law, and I cannot manufacture a new rifle that violates the above rules.
So...your lovely wife buys you a post-ban Bushmaster. It will look nearly identical, except it will only have the pistol grip and detachable magazine...all other items are going to be missing. We can argue about whether or not you
need those missing items later...your new Bushmaster is legal, and you may use pre-ban magazines in the weapon.
You may not, however, buy a pre-ban collapsible stock and put in on the weapon...though I think you could own one should TSHTF and the world end...this would make it an illegal "assualt rifle."
You may not own an AR-15 and also own the parts (trigger assembly) that would turn it into an automatic (ie, M16 parts). That creates a machinegun.
Finally, most people will always refer to these weapons as "assualt rifles" and no-one will correct them. I believe that the correct term is "battle-rifle", but let's not start using it, lest the liberals turn around and market them as a new, more lethal form of "assualt rifles"
In any case, your rifle will be legal should it follow the above mentioned rules.
Of course, the best thing you can do is spend fifteen minutes on your knees every night, asking God politely to let the 1994 bill quietly sunset in two years, and this whole silly mess will be relegated to history.
Hope it helps.