Same as "Brain Surgeon" but you need to get the kills with the Avril. No headshots are needed, just kills. Note: You cannot choose this gun in the mutator "Weapon Replacement" so a different approach is to use a second controller and set up a VCTF on Rails with no bots. The Avril on the ground in the loop of road your base surrounds. You can go to the enemy base and in two of the buildings that overlook their central road there is ammo that respawns for the Avril, making this much easier. Definitely one of the longer weapon kill achievements, however.
You can work on this achievement at the same time as Armadillo, Ace, and Deathwish also since they can all be done on this map. If you set the flags to 3, it will also help you progress toward 30 Minutes Or Less.