Banning the sale of long guns will not stop someone hell-bent on killing large numbers of people in one horrific event.
Most who have committed mass shootings (the Oct. 1, 2017, Las Vegas massacre excluded) are young males in their teens or 20s.
I have no doubt if AK-15s or AK-47s were banned, the mass killings would continue, perhaps on a much larger and deadlier scale.
Take away the guns, and bombs could be next.
Instructions for making bombs are readily available on the Internet, and the components can be purchased easily at local hardware stores.