The current Range Based Accuracy mod is highly flawed, in my opinion worse than the original system even after you adjust the accuracy of the weapons to compensate for its differences.
Problems with the mod:
1.) different shot types have different effective ranges. They should have the same effective range. There is already a difference in their listed accuracy. If you give them a shorter effective range, you should give them all the same accuracy.
2.) accuracy diminishes additively, that is, it goes straight to zero on a linear equation. An enemy too far away cannot be hit, except by a lucky "miss" which is extremely unlikely at significant ranges.
3.) there is no increase to accuracy from being closer. I could argue that this is even more important than having accuracy decrease from more range. Through playing many times, I always felt that the accuracy ratings for each shot type on any given weapon were about right for shooting a target a fair distance away. I rarely made shots from so far that it seemed odd for a snap shot to hit. MUCH more commonly, I would see a soldier unload an entire magazine of misses at point-blank range just because the accuracy for auto-shot said 15% chance to hit. Range Based Accuracy does nothing to fix this.
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We need a new mod which will set a specific distance as "standard distance" which all base accuracy values will be set for. A target at half the distance should have double the chance to be hit, while a target at double the distance should have half the chance to be hit. I vote the standard distance should be 20 squares. The hit formula would be:
(UA * SM) / (TD / SD)
In which:
UA = Unit Accuracy
SM = Shot Modifier
TD = Target Distance
SD = Standard Distance
If your veteran butterfingers Joe Miss-a-lot has 38 firing accuracy and is using a weapon with a measly auto-shot accuracy of 25%, then his chance to hit a target 2 squares away will be:
(0.38 * 0.25) / (2 / 20)
0.095 / 0.1 = 0.95
He'd have a 95% chance to hit the target. Now I know it's pretty difficult to fail to hit a target that close even with this cumbersome weapon, but Joe Miss-a-lot is capable of doing it...in one out of twenty shots.