HOW TO FARM THE RANK 10 AMR GRIM REAPER SNIPER RIFLE
We saw a lot of threads and discussions on this topic but everyone has finally agreed that the AMR Grim Reaper is the best Sniper Rifle in the game.
There are 4 spots where you can spawn the Facsimile Punisher (5 in truth but 1 is full of enemies and is really bad to farm here) but I suggest to farm this on the North one, the one near the Dome, since it's easier to run back and forth. I suggest to use a Sniper Rifle since they can hit pretty hard if you try to get close to them.
For a detailed walkthrough check the video below: