It's called Auto-Aim, NOT aimbot. There is a huge difference. It's also super easy to do, just edit the gun's projectile settings and set the curve extremely high. You can do it in several programs.
You can do this via Assembly [[Click here to view this link]]! Once you download assembly, open your map you want it on (Campaign) or Shared.map (Multiplayer). From here find the weapon you want from the [WEAP] tag section. Once you open the weapon tag you want click/hit the search button and type "Auto Aim". Change this from the default value to a larger number.