Every gun owner knows they are talking about fiction they got from hollywood. If the goal is to persuade gun owners to their position they should try not to sound ignorant.
There is no difference. Just call them what they are semi automatic weapons with high capacity magazines or make up a term that means exactly that, perhaps high capacity firearm. Then reduce the focus to the magazine capacity, which is what matters, and maybe something will get passed. Focusing on semi automatic like spurraider wants is just telling a whole bunch of hunters, ranchers, farmers that we gonna take your guns too.
We also really need to focus on the root cause of these mass shootings and it isn't mental health. There have always been crazy loser white boys and there always will be, not much you can do about it. Problem is they just don't have the work ethic of previous generations so they go for the quick fix of a mass shooting. Back in my day, loser white boys were just as crazy but they put in the time, effort, and planning to become successful serial killers. You just don't see that kind of dedication & effort these days.