There was a member here several years ago that hunted coyote with a 45cal air rifle. Sam Yang was the brand name but it looks like it is now called Seneca.
It's funny you brought this up since last night I was looking at videos on Facebook and there was a guy that was shooting a fully automatic Hastan 30cal rifle. I watched a few of his other videos and he had a 68 or 69cal rifle shooting a 700gr bullet. Thing tore a hole in a steel tank.
I'm not sure how much those ones are though. I'm sure something like that is every bit as expensive as a good rifle.