Although a more satisfying aiming point I’ve never found head shots a necessity in shooting rats, especially when they’re on the trot as they so often are, and I’ve shot a lot with an air rifle over the years. It seems that as long as you hit them square, in the flank or arse end with any rifle doing 10ft/lbs or more they roll over and die. They seem to go into shock very easily and if needed another follow up shot dispatches them.
Then I needed to justify it hence the rat shooting, holes in the cupboards and blood spatter.
Oh and the fact that I can't bring it back to the UK as it is significantly over the legal limit is a source of great disappointment. Stand to be corrected.