I don't know a lot about prebans, but I'd like to understand a little better.  I was thinking, if your gun is a preban, this will only be identifiable by the serial number...which only occurs on the receiver...and there is no way of knowing what configuration the pre ban was in, and even so it would be OK to change its configuration...

so, if you buy a pre-ban receiver, and install it on your gun, does this mean you can then install, for instance, a flash hider legally?

I guess, if your gun was, say a Colt, they could send the SN to Colt and see how the gun shipped from the factory.  Probably most other manufactures keep records that are similar so if they wanted to put in the work they could find out what parts your rifle had or didn't have.  Talk to ya' later.  TN.Frank

hmmm so if you have a preban lower you can not put a new and different upper on it? that sucks.

I'm not asking if you could use this to break the law, I'm asking if it would be legal.  I really wouldn't want to mess around with gun laws.

If you have a pre-ban lower, that left the factory as a complete rifle or was built into a complete rifle before 9-94, you can put a pre-ban upper on it.  You don't buy a pre-ban receiver and "install" it on the gun; the receiver [i]is[/i] the gun.  You install different uppers.  

There's a serial number list out there for just about any manufacturer that will tell you what S.N.'s were made before the ban (except Olympic - fire destroyed their records).  Even if the receiver is pre-ban, it's still possible that it left the factory as a stripped receiver and was not built into a complete rifle until after 9-94.  In this case, it would be a post-ban rifle.  

There's a legal section on the General board, and it might have an F.A.Q. about this.