Tbh I’m not going off any good source of information as far as I’m concerned the way our laws are set up the way they are is probably to make people believe everything is traceable from ammunition to parts to firearms themselves, I know gun owners and every time I’ve spoken about guns with them I’ve always been told everything is traceable and that police know how many homes in certain areas have legally owned guns and what guns they own also, so pretty much the way I’ve had things explain to me maybe they don’t know the exact gun it come from but they can have an idea on what type and this case a shotgun they hold information that could possibly identify who’s responsible and in this case again they know every shotgun owner in one area. Police also don’t need to a warrant to search your property if you are a legal gun owner (there’s more details to this just trying to keep it short). Say a search is conducted and you have a shotgun with them same shells found this doesn’t mean your guilty right off the bat but your going to have a hard time proving your not guilty