The JAK Maglift Kit is a new Aftermarket part added during Season 2, and changes the Haymaker shotgun into a room-clearing machine with an increased magazine and fire rate. Here is how to get the JAK Maglift Kit in MW3.
How to Unlock the JAK Maglift Kit in MW3
The JAK Maglift Kit attachment can be unlocked by completing five Season 2 Week 3 challenges. The five challenges must be done before the end of Season 2, or the Aftermarket part will then be moved to the Armory to unlock after the season.