Austin Petersen points out that you don't need one of the banned devices to do what the banned devices let you do.
- "Bump firing" is dumb. It sacrifices accuracy for high rate of fire. Such a trade-off only makes much sense in a few military scenarios involving units, not individuals (covering avenues of approach in a defensive position, forcing an enemy unit to keep their heads down while aiming shooters take them out in an ambush, etc.).
- BUT: Any ban on any weapon or part thereof is inherently evil. Individuals have the right to defend themselves, and the right to possess and use such equipment as they deem needful for doing so.
There's no "grandfather clause" and when it goes into effect the owners of the banned devices will be expected to turn in their gear within (IIRC) 90 days. I expect very low single-digit-percentage compliance with that demand.
I don't expect any real attempt to enforce it as such -- they'll just "enhance charges" against people nicked for other crimes (real or imagined).
If there are any organized attempts to track down and confiscate the devices, I expect we'll see a few dead bump-stock owners, a few more dead cops, and a quick declaration of victory and loss of interest in pursuing the matter further.
Which, frankly, may be the best possible outcome if it makes a few politicians re-think their more ambitious victim disarmament ("gun control") proposals.