No experience with Sigs. I used to live in CA. In order to get a hand gun shipped into the state, it has to be on CA DOJ's "list". http://certguns.doj.ca.gov/
To get on "the list", I believe 3 guns must be shipped to DOJ with a certain amount of $$$$. If the gun comes in various configurations- such as blued or stainless or scandium/aluminum, or various barrel lengths, or fixed sights vs adjustable or any other variations of any kind- 3 examples of each type to be sold in CA must be submitted along with plenty of money. Any time a gun is improved such as when Smith & Wesson adds a dash number, it must be resubmitted. I also believe the guns need to be resubmitted every couple years or so even if nothing changes.
One gun is kept sort of on file, the others are tested by dropping it on concrete from a certain distance. I want to say 10ft. but I don't remember for sure. If the gun passes the test and meets the other state regulations, it is placed on "the list."
I believe it costs several hundred thousand dollars per test to get a gun on the list. Some companies just don't sell in CA. Others pay the fare so they can access the market in CA. It is interesting to see some of the "cheep" guns the list was designed to eliminate, passed with flying colors and are available.
Used hand guns must pass the same test to be brought into the state for sale. If it is new enough to be on the list, it is fine. If it is an older unlisted model it is not fine. This rule essentially eliminates used hand guns from out of state being sold in CA. Things have changed since I left, but it seems used hand guns not on the list, can not be shipped from FFL to FFL within the state. So you must buy locally or be prepared to fill out the forms one day and come back 10 days later to pick up the gun. If the gun is at a shop 300 or 400 miles away, this can be an inconvenience to say the least.
When I lived in CA, long guns did not have to go through this test. They just had to meet the configuration regulations concocted by the goof balls in the legislature. I do not believe there is a "list" for long guns.
If all this seems new or unreasonable to you, consider yourself fortunate to live in a free state. You would do well to insure it stays that way. After 30 years of fighting the idiots in Sacramento, I cast my final vote with my feet. I quit my job and fled to Oregon. The streets are not paved with gold here, but it seems to be harder for the gun grabbers to get traction here.