Please limit your comments to areas in which you are knowledgeable. It is possible to bump fire a totally stock AR-15, or to make it a bit easier with a rubber band added to facilitate the bumping motion. This is not an illegal modification.
I don’t claim firearms knowledge but seriously people all over this country have been targeted by the feds over firearms alterations and at this point in history they may just throw people in jail for those rubber bands and let the court system figure it out later.