David, no, the gun must be on the CA DOJ roster. https://oag.ca.gov/firearms/certified-handguns/search .......CA compliant guns at Bud's here >>>> budsgunshop.com/search.php/type/Firearms_Handguns/exclusive/ca

No in order for a handgun to be CA legal, the manufacturer must submit the gun to testing from the CA Department of Justice. And it has to be certified compliant, unfortunately the CA DOJ has not let any manufacturers submit guns for testing in several years. So you need to find a pistol that's already certified. The APX was released after CA put a stop in certification, so its not on and can not be made compliant for the approved handgun roster.
All CA compliant handguns buds carries are listed here
budsgunshop.com/search.php/type/Handguns/exclusive/ca

The main issue is deeper than magazine capacity, no models of the APX are currently on the roster of handguns certified for sale so it cannot be shipped to civilians in CA. Your only options for off-roster guns are purchasing one from someone in law enforcement who can legally order one, or purchase one from someone who already has one from purchasing in the aforementioned way or moving to CA from a state where the gun was permitted. Here is a link to the roster: https://oag.ca.gov/firearms/certified-handguns/search?make=151008

NO, Beretta APX is not on CA DOJ pistol roster thus is not CA compliant. It is not legal even with the magazine removed. Check the roster HERE ( https://oag.ca.gov/firearms/certified-handguns/search?make=151008 ) I hope this helps.

David, no Sir. It must be on the CA DOJ approved Roster to be legal. There are no current APX's on the CA DOJ Roster : https://oag.ca.gov/firearms/certified-handguns/search?make=151008