This answer applies to the PS3 version of Far Cry 3.
Bullets in Far Cry 3 travel a maximum of 152 meters.
How I tested it:
- Fully upgraded Z93 sniper rifle
- All skill upgrades unlocked
- Targets located at the house 300 meters west of Break Point Docks safehouse
- Firing from the radio tower northwest of Break Point Docks safehouse
Experiment 1: Wanted Dead
I began the Wanted Dead mission near Break Point Docks which requires you to kill two heavy troopers near a house. I approached the mission location from cover until the mission activated. I then tagged the targets and climbed the hill to the radio tower overlooking the target location. My minimap indicated that I was 180 meters from the mission location. I took aim and fired five rounds directly at one of the marked targets, with no effect. I then moved closer in five meter increments, firing three rounds at each interval until an effect was noted. The distance from me to the mission location at this time was 150 meters.
Problems with this method: I realized that although I was 150 meters from the mission location, my targets were not standing precisely at that location at the time I fired. Also, at 150 meters from the mission location, an alert pops up instructing you to return to the mission zone or the mission will fail, and I didn't know if mission restrictions were limiting the range of my rifle. Therefore, I abandoned the mission and took another approach.
Experiment 2: Friendly Fire
I next decided to try firing at a moving target. Since I had already cleared every outpost, I decided to shoot at Rakyat patrols. I climbed the radio tower northwest of Break Point Docks, used the sniper scope to acquire a Rakyat vehicle as it drove past the target location, measured the distance using the map, and opened fire. There was no effect. However, I quickly realized this approach was flawed, since with the target vehicle in motion, there was no way to guarantee that I was consistently scoring hits.
Experiment 3: Kick the Tires
I realized that I needed a target that was both stationary and would react visibly when hit. Dune buggy tires fit the bill nicely. I parked a dune buggy at the target location, set it as my destination so that I would have a distance readout, and then climbed to the radio tower again. This time, I knew that the target would not move and the distance displayed on the minimap would be the precise distance to my target. I began firing at 160 meters, moving 1 meter closer every three rounds.
At 152 meters, my first round destroyed my target, the tire of the dune buggy. I backed up to 153 meters and was unable to shoot the other tire. I moved forward to 152 meters and destroyed the other tire on my first shot.
In the PS3 version of Far Cry 3, at least, bullets travel a maximum of 152 meters. This value is the same whether or not you are in a mission.