Despite the detailed sets of information provided by the Wiki, there is one vital set of information missing: falloff range. From the many weapons I use, I strongly see how the kill possibility of weapons with accuracy of 1 significantly go down at longer distances. I know that there has to be falloff range, the distance where guns bullets starts to lose effect. Is there data provided for this?

In the code for the weapon, "kill_decay_end_time" is when the bullet will completely loose all chance to harm anyone. This is dependent on the speed of the bullet as well, so two weapons with the same "kill_decay_end_time" might have a different max range depending on the speed of their shot. You can do some simple math to find the maximum range.

There's also a "kill_decay_start_time" which determines when the bullet begins to loose the kill potential.

That very important piece of information is not included and must be added.

The data are all in the weapons file.

Here an example for the G36, the important parts are marked in yellow color:



The bullet starts to lose effectiveness 0.35 seconds after the bullet left the gun barrel and has no effect anymore after 0.70 seconds.
When you consider that the bullet speed is 100 m/s, the kill decay is starting after 35m and the bullet is ineffective after 70m.
A widescreen represents roughly 50m. If you consider that without any sight range modifier (like e.g. a sniping rifle has), you can point your crosshair at about 80% of the screenwidth (I don't have the exact values right now but for sure close enough, though I won't take that into consideration and take the case where a soldier shoots from one end of the screen to the other). It also takes consideration of vertical coordinates, of course but to make it simpler, we'll just consider a totally flat terrain.
With this example, the probability that you kill a soldier with a G36 when you are aiming with the crosshair the farest possible in screenwidth, you'll have a kill probbaility of: kill_probability * [(kill_decay_end_time - "kill_decay_time_at_screenwidth") / (kill_decay_end_time - kill_decay_start_time)]
"kill_decay_time_at_screenwidth" being screenwidth / projectile_speed

In our case the proba is 0.5 * (0.70 - (50 / 100)) / (0.70 - 0.35) = 0.2857 which is a ~28% kill chance

From that, you could make a bullet travel chart to visualize the bullet decay over time for the different weapons.

In the image below you can see what I did with The_Soldier for the DDay mod to balance the weapons. The x-values are the bullet travel distance, rather than the bullet travel time but it's just a factor at the end.
If someone has more interest in that subject and knows a bit about coding, a program for that could be written so that it would automatically parse the values from the *.weapon files in the weapons folder and enter draw a chart.

someone really need to add effective range on the wiki. understanding our weapons better help improve their performance. I guess I shall put myself up to the task of it.

The thing is, range is kind of pointless since there's no way of measuring it in-game. The only reason Jack made that chart was that range was more important in the mod with the introduction of mainline SMGs, and being able to compare them to rifles in some manner was necessary. In vanilla RWR, most guns will simply be able to kill as long as you can see the enemy and you have ammo in your weapon - 90% of all weapons can kill to the edge of the screen. Beyond that, it's all up to RNG.

So, in the end, I don't think having range on the wiki is going to help very much. There's just nothing to compare it to and 90% of weapons don't have a practical limited range.

Every weapon can kill, but for example, a pistol with the same max kill chance as an assault rifle might have different effective range. Its still a good idea to put out some quantitative data get a more in depth look at the effective range of weapons.

I know how to perceive distance in game roughly but not precisely, this could let me know when the weapon I'm using is not going to be effective and let me adjust my distance more easily to utilize the kill chance effectively. so range is quite important to me.

Every few percentage point counts, I want to make sure I could utilize the kill chance more effectively.

aww crap, theres so many, itll take me forever to calculate.

jack please write the formula down for me?

I retyped your calculations on my graphing calculator and it gave me a .05
somethings not right.

I wrote the formula in my last post. Why should I write it again?

could you verify your calculations? i did the same and it did not give me the result you got.