How is weapon accuracy interpolated between ranges?

The wiki lists the accuracy of each weapon at ranges of 4, 15, 30, and 50 tiles. It also says:

Between those ranges, accuracy stats are interpolated.

How exactly are they interpolated? Also, how accurate are weapons at below 4 tiles distance?

The in-game stated accuracy of the starter pistol and bolt-rifle.

Range          3  12  25  40
PistolAcc     80  75  45  35
BoltRifleAcc  65  80  90  80

When at distances less than short (3), the short range applies. So a pistol has 80 accuracy from 0-3 range. You can see this via the accuracy tooltip, by moving next to a squirrel and aiming.

When at distances between two numbers, the accuracy is a weighted average. A pistol has 79 accuracy at range 4 and 78 accuracy at ranges 5 and 6. It is likely that the number is rounded for display purposes only, and the unrounded weighted average is used in the calculation.

The wiki has been updated with these ranges and accuracies, as well as with an explanation of how accuracies are interpolated. I believe it to be reliable at this point.