I'm not in favor of Bump Stocks but I am curious as to how banning the sale of something that the industrious can make in their basement is going to serve any purpose?  Seems to me that allowing the sale and registration would allow you to track those accumulating large inventories.  
Law passage is a lot of wasted talk and energy to appease the hand wringing, overly emotive among us.  People we need to protect from themselves. Congress has better things to do then pass new gun restrictions that only serve to handcuff the law abiding. 
You have to love the stupidity of the pass a law crowd.  A criminal is a Law BREAKER.  What do you suppose that criminal is going to do with your new LAW?  If you guessed BREAK it congratulations you are not a hand wringer.  You will never stop the criminally insane, who contemplate and carry out mass murder, with laws.  You might if you identify them accumulating a whole bunch of Bump stocks. We need to stop the madness of the Pass a law crowd.