If a person goes through the hoops to buy a registered bolt--say, for an UZI--does he also have to register the SMG in which the bolt will be used? This question is a little confusing...
I noticed that you said "...does he also have to register the SMG in which the bolt will be used?" If the gun IS an SMG it must be registered. Since the gun is registered the bolt does not have to be registered, though it is OK to put a registered bolt in a registered gun. It is redundant.
If you meant to ask "Does one need to register a semi-automatic UZI to use it with a registered full-auto bolt installed?" The answer is no. The bolt converts the whole gun into a MG while it is in the Uzi.
The bolt can be moved from gun to gun but please note that while the registered bolt is in a gun, that gun CAN take on characteristics of a MG (very short barrel, etc.) AS LONG AS the bolt is in the gun. If the bolt become separated from the gun, the gun is now subject to all laws regarding barrel length, etc. Be careful with that!
Please be aware that it is NOT possible to register any new MG bolts, receivers or full-auto conversion devices. This ban has been in effect since May 19, 1986.
Any registered MG bolt, receiver or conversion device made before that date can still be transfered as long as it is on an ATF form 1,3 or 4.
Also, registered bolts and conversion devices can be repaired but NOT replaced. If the bolt/device is destroyed beyond repair (or serial number is destroyed), you are screwed.
My "Thompson" is made this way. It has a registered full-auto firing pin in it. As long as it stays in the gun, I can keep the MG barrel on it without having to register the gun as an SBR.
atc310r is correct- the ATF is the ultimate source for any info on this matter. When I had my gun made, I got I letter from the ATF firearms branch that states what I mentioned above.
Norm
http://i6.photobucket.com/albums/y204/mbsennett1/ATFletter1.jpg
http://i6.photobucket.com/albums/y204/mbsennett1/ATFletter2.jpg