5 0 0You may be able to get this as soon as the prologue, as there is ample opportunity. You will at least have made significant progress. leans out if you are in the passenger seat, shoot as normal. shoots if you are in the drivers seat.
3 0 0I was able to get the achievement to pop by grabbing on of the PEGGYs tucks with a gun mount on the back and then driving until I came across some bad guys (or waiting parked in the middle of the street) and getting on the gun in the back and killing them. This counted as "leaning out" the vehicle and I picked up the kills I needed easily to unlock the achievement.
1 0 0You can get this very early on in the campaign.You will come across a part when your fellow deputy will ask you to get into the truck. Get into the truck pause the game and set your game difficulty to easy. Shoot as many enemies as you can (aim assist really helps). If you do well at that part you can easily go over the amount you need for this achievement to pop.
