The bump stock ban rule is out. Bump-fire stocks are now machineguns. To power-crazed tyrants, anyway. But, since FOPA forbids possession of machineguns manufactured or imported later than May 1986, you’ll have to get rid of them.
You want to be good, right?
I suppose you could simply destroy your bump-fire stock, but if the ATF gets hold of some retailers’ customer list and comes knocking, you’ll want some proof that you already complied. You could hang on to the properly cut up pieces (you do have an oxy-acetylene torch?) and show them that.