http://gqyegcar7pyqae6mo32so7za4bfw4cegj4pwn5ou2cicmotldobjjayd.onion/777
I imagine this survey only takes into account registered guns (or else how would they know they exist?), and there are a lot of unregistered firearms in barns, bunkers and attics all over eastern europe. The countries at the very top of the graph have long traditions of citizens militias, sports shooting and hunting, which gives reason for firearm ownership to be recorded and licensed.