My reply was a little confusing - I was researching CA and US gun laws yesterday with the personal objectives that I stated, but my comments about 18 USC 922(a)(5) and such were a response to azredhawk's proposed scenario where a (presumed) non-FFL goes to another state and sells a rifle to a (presumed) non-FFL resident. I was agreeing with your analysis of the seller's legal exposure, but not with the conclusion that the buyer was in violation of 922(a)(3).
With respect to my interest in purchasing a long gun out of state, in CA, 12072(d) requires that where neither of the two parties are CA legal dealers, that the firearm transaction goes through a CA legal dealer. Since the out of state FFL can't be a CA legal dealer, the Fed exemption that allows an FFL to sell to an out of state resident isn't satisfied. There are many exceptions to 12072(d) including one for transfers directly from a CA private party to an out of state FFL, but not one that would permit an out of state FFL to transfer directly to a CA resident. Out of state FFLs can transfer to a CA legal dealer, but since July 2008 now only by first getting a free authorization code from the CA DOJ that says the CA dealer is CA legal. Buying out of state and having the FFL send the gun to a CA dealer (and paying the ~$30 state fee and usually a minimum $50 dealer charge) is the way it gets done.