I've fired a Kalashnikov without a bump-stock, max 5 rounds and you can bump fire it on your hip without any add-on. It's not super accurate, but you can fire it fast without having to modify it at all.
These types of guns are ridiculous and have no real purpose in society. If you talk to Creedo he'll tell you everyone should be armed to the teeth to prevent the government from being tyrannical but I'm pretty sure he's stuck in a 1776 revolutionary war re-enactment.