I believe an MG would fall under the definition of an SBR in the definitions in the SDA (barrel <16" and a rifle) so yes.
But if you had your CCW, the SDA may allow you to carry your -16 mag loaded in your car. I'm no lawyer and I don't have title 21 in front of me right now so you have to make your own choices.
OK, G18 or that beretta 93R?