Campaign: Dark Carnival
Level 4: The Barns
You will find this Whack-A-Mole type game before you leave the gaming area and head into the barns. If you have closed captioning on you will see when the game is close. Walk up to the machine and press to start the game, either using a gun or a melee weapon to hit the popping heads.
You will need to continue the game about three times to read the target score of 42. Just keep playing until the machine shorts out and breaks. The achievement will unlock once you break the game.