Where did u get that info?  You can own both pre-ban and post-ban AR15.  You just can't install pre-ban upper receiver on post-ban lower receiver.  

it is totaly legal to own prebans and postbans at the same time, it would be a little shaky to own a post ban gun and have an extra preban upper or CAR stock laying around. but as long as you have a preban you can have as many preban and postban parts laying around as you want.

How can it be "a little shaky" to own a postban gun and have extra preban pieces "laying around"?  No shakier than having complete rifles that you can switch out in less than a minute.  Please don't tell me about the so-called constructive intent---that rule does not apply to anything other than Class 3 weapons.  Lets not make up the law as we go---there is enough of that in this forum already.  Kissel out.

Kissel -

I can't access the US Code site now (I'm doing this from memory, so I may be slightly off), but as I recall 922(v) (1)  proscribes the manufacture, transfer, or possession of a semiautomatic assault weapon.   "Manufacture" is not defined in 921, and I know of no cases examining the term "manufacture" as used in Title 18, but after reading Thompson/Center, I have little doubt "manufacture" in Title 18 has virtually the same meaning as "make" in Title 26.  And while Thompson won their tax refund, the Court noted that "make" could include possession of an unassembled quantity of parts.  Certainly its arguable that "manufacture" under Title 18 only includes the act of making for profit or distribution, but its a shaky argument and you could still be prosecuted and forced to defend against it (at great expense and risk to your freedom).  It also doesn't consider the term "distribute" in the definition of "manufacture"; a term which could be defined so narrowly as to include distribution to one or more persons, including yourself.

I agree that if you have both a preban and a postban with spare preban uppers, I think you'd be fine.  However, if you only had a postban and spare pre-ban uppers, I think you'd definitely be treading on thin ice.