Factorio Forums

Shooting enemy units with weapons that cause less than zero damage (due to resistances) will heal the enemy if they are hurt. An example is using regular bullets (2 physical damage) against medium biters (4 physical resistance).

This does not seem to be the case when shooting buildings, instead a very small amount of damage is done.

I tested that, and I think that it is not the case.

I wrote a small info about how the damage and resistances work.
https://forums.factorio.com/wiki/inde ... tle=Damage

I believe that the damage dealt is just very small and the enemy autohealing is higher.