Some bad info here: Maybe I can save someone if hey are following it themselves.
The Sa58 is a bit more complicated; if the reciever (the actual gun with serial number) is not listed on the California DOJ list of named assault weapons then it can be imported provided that the mag requires a tool to remove it and it doesnt have a capacity greater than 10 rounds.
Making the FAL CA compliant shouldnt be too bad, though. DOIJ says the magazine is not detachable as long as it requires a tool to remove. So you could weld like sheet metal around the mag release button, too big for a finger to fit through, and then make it so you have to put a metal rod through to get the magazine out. You could attach the metal rod to the pistol grip, too.
It is my understanding that an "assault rifle" that is fixed with a magazine that "requires a tool to remove" becomes an illegal assault rifle when you remove that magazine. So unless you can load it without removing the magazine your still in illegal possession of an assault rifle when you remove the magazine without properly removing the barrel and other things first.
The way the people getting around it are legal is because rifles like AR-15's split open and can be loaded that way without ever removing the magazine. The "tool" wording is to describe the definition of a "permanent" magazine. As soon as you remove the magazine to reload you have an illegal assault rifle in your hand. If seen doing this by a LEO (or someone else that charges you or uses survelience to show you did it at the range) you can be charged with multiple felonies.
So I certainly hope people are not using a tool to reload, or your illegaly possessing assault weapons, and you are commiting a felony when you reload.
Professor K your interpretation of the law is very wrong. Having the tool attached to the gun for reloading would make you a felon each time you reloaded.
As soon as the "permanent" magazine is removed, and is not done with other parts of the gun removed first, it is a felony assault rifle with a detachable magazine. This is why they must be sold with the "permanent" magazine in the rifle. In fact they have talked of legislation requiring welding to be considered "permanent" because people can easily turn them into illegal assault weapons too easily.
The fact that you can remove the magazine with a tool never makes it legal to remove the magazine unless stripping the gun, and it is
still illegal if you strip the gun in the wrong order. There is a very specific order to strip such a gun to not be commiting a felony.
I repeat the only reason you can legal have such a weapon is because the magazine is "permanent" removing the magazine makes it not permanent and makes you a felon. The definition of permanent is only a side factor and does not change the legality of a removed magazine on a weapon that is only legal because of the "permanent" magazine.