This is a fun topic. Devil Dog is not wrong when he makes the distinction that he does.
BUT! Our overlords at the MDGA do clarify this (and pretty much only this):
If you have an assault long gun ("copy"), it cannot become a copycat weapon by definition. This is how the MSP interpret things, too, to my knowledge.
A person who lawfully possessed, has a purchase order for, or completed an application to purchase an assault long gun or a copycat weapon before October 1, 2013, may: (i) possess and transport the assault long gun or copycat weapon; or
BUT! Our overlords at the MDGA do clarify this (and pretty much only this):
“Copycat weapon” does not include an assault long gun or an assault pistol.
If you have an assault long gun ("copy"), it cannot become a copycat weapon by definition. This is how the MSP interpret things, too, to my knowledge.