We passed a similar law here in Kansas about three years ago, when they started building upscale homes near a shooting range that has been outside the KC area for generations. I know Minnesota is a liberal state, but it's also very rural. I hope you don't have too much trouble getting it passed.
The problem is that the "canoe counties" at the north end of the state are both very rural and very liberal, and they tend to vote en bloc with the very liberal urban counties on most issues. Range protection isn't an issue to voters outside of the metro area because when the locals want to shoot they just step outside, make sure their favorite cow or pickup truck isn't in the line of fire, and blast away.
It's a big issue in the 7 county metro area, and the biggest problem is that we have this unelected body called the Metropolitan Council that functions as a central planning commissariat and makes -- or at least tries to make -- all zoning and land-use decisions for the entire area. The Met Council talks a lot about "preserving green space" and "controlling urban sprawl" and all that, but in reality it's full of "smart growth" advocates who basically want to turn the whole region into a 100-mile wide swath of rigidly planned post-suburbias connected by light rail.
Of course, things like shooting ranges are anathema to the Met Council. We can't have guns in our brave new world, y'know.