41.77.9
Singleplayer
Mods used are: Combat Text, Show Weapon Stats, Mod manager. Bug is reproduceable with no mods but its harder to see on just the debug console
Old Save, but applies on a new as well
Reproduction Steps:
In the items.weapons.text file, change the stats of whatever gun you want to test do have a crit multiplier of 1, hit chance of 100%, max damage of 1, and min damage of 1. The bug still happens regardless of this, but it makes proving it much easier since you don't have to deal with random damage spread or missing. You can change some of these in the debug editor, but not all.
Shoot at a zombie at near point blank range. I've seen it go as low as dealing 0.21 damage from about 2 tiles away. Make sure the zombie is facing you and isn't wearing clothing, as otherwise external factors will affect the damage. Also make sure you don't shoot the same zombie more than 3 times as the natural damage rampup from hitting a zombie multiple times will start to take place.
Shoot at a zombie from max range. You will see that it does far more damage, even surpassing the weapons base damage. The highest I've recorded was 1.31
Video Link:
I believe this is unintended behavior not only because it doesn't make sense for guns to be using this system thats for melee weapons (You can see its the exact same system by editing a melee weapon to have 1-1 damage and 10 range or so), but also because guns range increases as you levelup aiming. This leads to a rather odd behavior where a gun deals more damage at what used to be its max range at lower weapon levels, and less damage as its range extends. I was able to reproduce this issue as a demonstration.
Video Link:
I tried going through a decompiled copy of the code in order to try to figure out what was going on, but I wasn't able to definitively figure out what it was. My best guess would be that the isRangeFalloff property might not be being properly applied, but that could just be related to something else entirely. Hopefully this won't be too hard to fix!