You can bump fire a semi-auto rifle from the shoulder with the help of a rubber band. Semi-auto rifles can be bump fired even without using any add-on aid. Even semi-auto pistols can be bump fired.
The gun grabbers won’t be satisfied with banning bump-fire stocks. I expect they’ll be pushing hard for severe magazine capacity restrictions. They might even try to ban semi-automatic firearms altogether though that would probably be almost impossible for them to achieve.
Yep, a simple velocity trigger and a loose grip will get you going bump firing.