Wanting to buy a assault or carbine rifle. Help?

Forget about ever getting a rifle with a detachable magazine in your state. Look into getting yourself a Mini-14 for around $700. It fires the .223 (same as AR's) and comes in a completely California-friendly version with an internal 5-round magazine. In your state, you wont be able to get a collapsible stock or threaded barrel, but if you truly wish to use this weapon for only lawful purposes then these should be non-issues. As far as upgrades go, a match barrel and optics will let you put a bullet in a flee's @ss at 300 meters, a la GySgt Highway!