To make an "assault weapon"....
Fill out a form 1 stating your intentions. Get the CLEO signature, Pay the tax.
when it gets back:
buy the Parks kit (say a AK-47/SEMI-AUTO ONLY)
bend/machine/forge the receiver yourself
slap in the parts and the Short-bbl (making it NFA)
engrave the serial number you designed/devised.
shoot the piss out of it. Its legal.
CR 922 says that you have to have so many US made parts in your assult weapons (at least 10 I believe - non-NFA). There is no law (that I know of) that limits a SBR/SBS.
Unless you have a 07 FFL/C2 SOT status (FFL = 150.00/3 years & SOT=500/year) you cannot make or convert a SMG! Even then you can only make them for R&D. You CANNOT make them, even with an SOT, for the sole purpose of personal shooting! They HAVE to be made for sale or for R&D. These are called post-sample machine guns, and have to be sold to Law Enforcement or Military UNITS or to other SOT's with a special letter.
You can obtain the FFL/SOT from your home. FFLs used for gunsmithing and internet sales do not require the storefront properties. The BATF&E do NOT want people selling guns from their home... not retail at least.
A C3 Sot cannot make or import - just sell, a C2 sot can make and sell, cannot import. An Importer can Import and Sell, but not make. home this helps.