I have not failproofed this, I have done it every time I try though. You need six grenades, a silver pistol, and a sniper rifle.

Go to the Rifle range in the pub. The one that you meet the five members who are Sato's friends and are trying to kill the man who recieved your girlfriend from the prick in the red suit.

At the rifle range, use the Sniper Rifle on the range by hitting the button under the counter while holding it. Then once it is in the last 5 seconds or so, hold A to keep zoomed in.

Once it ends you should have the sniper scope image pasted over your reticle. Enjoy your wasted time.