What is a wolf 40 cal rifle?
You can bet the news writer is clueless. I was thinking a black powder rifle or the Italian "lupira", which is a coach type shotgun.
Think the modern version of Davey Crockett or Daniel Boone. The Wolf is an affordable, modern cap and ball rifle available from BassPro and Cabela’s as well as some WalMart and Meijers chain stores.
(Larger picture at link below)
This one is a .50 cal, and goes for $149.99 at Scott Outdoor Sports
It's not legally (for federal purposes) a firearm, so the usual "gun control" laws don't apply. You can order it shipped direct to your home, just like you could any other firearm before 1968 (other than machine guns).