I apologize in advance, I realize that people probably ask these questions all the time. But I am new to ARFCOM and Calguns.
  1. Aren't AR-15 type guns banned by series? What is "series", does it mean AR-15 type guns regardless of manufacturer?
   2. Am I correct in assuming that even though the gun dealer I used to handle the transfer paperwork recorded the serial number and registered me as the owner of the Stag 15 receiver, it is not a registered rifle? If it indeed is not registered as a rifle what is it registered as?
   3. Can I register the rifle I build as what ever they want to classify it until they declare it an assault weapon? It seems to me it would save everyone alot of hassle if I had some paperwork to show to the police officer. Especially me, I'd rather not spend the night in jail while they figured things out and confiscated my rifle.
   I think these are legit. questions. Please no replys from hard a** cool guys who think giving one liner answers makes them manly. Pound your chest elsewhere.
   Thanks.

Read the primer tacked at the top of the page. The Kassler/Harrot court decisions found the wording of the original law overly vague (i.e."AR-15 series") and require firearms to be listed by maker and model to be enforcable.

Thanks.
 

 This pamphlet is the 2006 Cali Firearms Laws btw.

On Calguns, you'll probably want to read the FAQs on the first page.  It should be able to answer most of your questions.

link

Ignore the parts about "if it's declared an AW", as the flood of OLLs clued them in to what we wanted.  Instead of pinning a mag, IMHO it's much better to go with a MonsterMan grip or U-15 stock to maintain detachable mags for all the 30 rounders you bought before the ban.