California isn't fond of flash hidders/suppressors but there are some compensator/suppressors like the PWS FSC and Battle Comp that are legal in those states. I think flash and sound suppression should be gtg w/o a stamp in all 50 as well as standard cap (30 round) mags.
In California, flash hiders are considered an evil feature. So if you have one, you need to have a fixed magazine. If you don't have a flash hider, any sort of pistol grip (forward or rear), or a collapseable stock, then you can have a regular magazine release. If you have any of these EVIL features (lol) then you magazine must be fixed and must require a tool to drop the mag.
best cheap flash suppressor if your not running a qd suppressor is the A2 military flash hider. you not only get a great flash hider but it prevents dirt kicking up and blocking your view or giving you away when shooting prone.
also keeps from damage the paint on the hood of your car when using it as a hasty rest. dont ask me how i know that....