I'd also like to point out that bump stocks are *probably* already illegal in MN, although there's been no test case yet. Unlike the federal machine gun ban, MN also classifies "trigger activators" as machine guns:
"Trigger activator" means a removable manual or power driven trigger activating device constructed and designed so that, when attached to a firearm, the rate at which the trigger may be pulled increases and the rate of fire of the firearm increases to that of a machine gun.
https://www.revisor.mn.gov/statutes/cite/609.67
A bump stock is a removable device that was specifically constructed and designed to increase the rate of fire to that of a machine gun when attached to a semi-auto firearm. The only ambiguity is the meaning of "trigger activating". Technically, the stock doesn't activate the trigger directly. Some other object that isn't a part of the bump stock must be used as a mechanical link between the finger stop on the stock and the guns trigger. In theory that object could be anything, but in practice it's pretty much always the operators finger. So the legal question is does the absence of the mechanical linkage between bump stock and trigger let bump stocks "off the hook" as being trigger activators. My humble guess is no.
A firearm thats completed more than 80% is considered to be a firearm. A bump stock, minus the linkage that activates the trigger (the shooters finger) is most certainly more than 80% complete. So my guess is that if a test case were to occur, the courts would find bump stocks illegal in MN.
For those who come back with a counter argument of belt loops, a belt loop isn't installed on the firearm, where a bump stock is. For those who come back with rubber bands or shoe laces or similar devices installed externally to the firearm, those devices were not specifically designed and constructed to increase the rate of fire of a firearm, where a bump stock is. Bump stocks *probably* meet the statutory definition of a trigger activator, but none of the other things people commonly use to bump fire a gun do. A bump stock is unique in that it is both installed on the firearm, and was specifically designed to increase the rate at which it can be fired by most operators.
It's possible a good lawyer could argue the point that because bump stocks lack the linkage that actually operates the trigger, it's not a trigger activator. But I wouldn't bet on it. Especially not with the makeup of the MN courts.