I’m sure there are some statistics out there about guns confiscated for crimes. If you have a link to actual data, I’d be happy to be proved wrong.
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.