I think you are right. Long guns are not usually used to commit crime. Again, it depends on what the government wants to do first.
Also, what I propose here is classifying weapons differently. You used the expression “assault weapon”. It's very difficult to define an assault weapon. I think the law should categorize weapons or firearms by the way they are handled or manipulated, if you want, and the way they shoot. Semi-automatic weapons and self-loading weapons with detachable magazines are way more dangerous in the case of mass shootings.