There are some studies. The easiest is the FBI statistics on homicides, which show that handguns are the most common guns used for homicides (about 50%) , with shotguns a poor second (about 3 %) and rifles of all kinds a distant third (about 2%).
Semi-automatic rifles of military appearance are used in one percent or less of homicides.
My comment was on cheap as opposed to expensive handguns being used.
BTW, how does 50% + 3% + 2% add up to 100%? Is there some third category of firearm of which I’m not aware?