A rifle with a "bullet button" is considered to be a "fixed magazine" as the law is written, and apparently the DOJ has gone on record confirming that interpretation. With a bullet button, some "evil features" such as pistol grips are allowed. Without a bullet button (aka Ruger Mini 14, M1 Carbine), the rifle must be "featureless", i.e., cannot have any evil features such as a pistol grip, forward vertical grip or a bayonet lug. (why anyone cares about bayonet lugs is beyond guessing.)
[It is considered "fixed" because of the peculiar way that the law is written, which defines a fixed magazine as one which requires a "tool" to remove. A bullet button requires some sort of tool--such as a bullet--to be inserted into the mag release to remove the magazine.] [There was a bill submitted last session to ban bullet buttons and redefine "fixed" as meaning that the gun had to be disassembled to remove the magazine, but that bill as withdrawn. It is technically still capable of being reintroduced this session before it is officially dead. The sponsor of the bill, Senator Yee, is termed out, and he may try to make this his "legacy."]
