Hell, it's a very good idea to keep them separated if not being used and even if you have it registered. I would use a shotgun or pistol for home defense, just to get away from having an assembled AR in the house.

Look at it like this, some people have RAW's, some have BBAW's and some have featureless AR's. If none of them are together, they're just parts (uppers) and a serialized firearm part (lowers). Neither will work unless they've been put together to make a functioning weapon.

You could number a couple different gun cases to match up with one another. That way when you go to the range, you grab the correct cases. Get to the range, put them together and do your shooting for the day. When you're finished shooting, take them apart and put them back into the correct cases.

Just be thankful that CA does have a constructive possession law regarding this. Is all of this a pain in the ass? Of course it is but dealing with CA gun laws is a bigger pain in all of our collective asses!

Just remember to be safe and dont give these fuckers the opportunity to fuck you over. And you know they will because we've already seen examples of it!