LOL! So, my guess is that if you "leave in" the bullet button so that the BB functions like a standard mag release, then you have a detachable magazine. However, if you use to drop a mag and remove it from the BB and attach it to the dust cover, then you do not have a detachable magazine.
However, when the cops show up and take it off your dust cover and put it in your BB, then you got "issues."
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