When controlling a pawn and hovering over most sorts of entities you might want to target, the game will display hit percentages with a breakdown of all the factors that affect your odds of hitting that thing. When pointing out a mini-turret, it is shown that mini-turrets benefit from cover, with a percentage breakdown of the cover provided by any items placed in between the turret and the attacking pawn. In actual practice though, turrets do not benefit from cover at all.
A simple bit of XML tweaking will allow you to create an item that offers 99% cover, which will correctly block 99 out of every 100 shots fired at a pawn standing behind it, but a turret placed behind it will not benefit from this cover at all. Sandbags, chunks, fences, it doesn't matter what item you're talking about, pawns always shoot at turrets as though the shot was completely unobstructed, which conflicts with what the tooltip says.
I'm actually not sure what the intended behavior is supposed to be. Either the tooltip is incorrect and turrets are not supposed to benefit from cover except in that it slows down melee pawns who are attempting to reach the turrets, or turrets should be benefitting from cover and should be twice as hard or more to shoot down from a distance when placed behind sandbags or similar objects.
To test ingame: Start a new encounter/map, god-mode spawn in two mini-turrets with appropriate power supplies, surround one with cover and have the same pawn gun each of them down, comparing how long it takes. Even over a small number of trials it should obviously take twice as long on average to destroy a turret which is behind the 50% cover of a rock chunk, but despite what the tooltip reports in that regard there is no difference whatsoever.
For reference, I believe this has been the case since at least version 1.0, and that's just the oldest easily accessible video I found on the topic before testing it myself after some folks on the Discord were talking about it.
A simple bit of XML tweaking will allow you to create an item that offers 99% cover, which will correctly block 99 out of every 100 shots fired at a pawn standing behind it, but a turret placed behind it will not benefit from this cover at all. Sandbags, chunks, fences, it doesn't matter what item you're talking about, pawns always shoot at turrets as though the shot was completely unobstructed, which conflicts with what the tooltip says.
I'm actually not sure what the intended behavior is supposed to be. Either the tooltip is incorrect and turrets are not supposed to benefit from cover except in that it slows down melee pawns who are attempting to reach the turrets, or turrets should be benefitting from cover and should be twice as hard or more to shoot down from a distance when placed behind sandbags or similar objects.
To test ingame: Start a new encounter/map, god-mode spawn in two mini-turrets with appropriate power supplies, surround one with cover and have the same pawn gun each of them down, comparing how long it takes. Even over a small number of trials it should obviously take twice as long on average to destroy a turret which is behind the 50% cover of a rock chunk, but despite what the tooltip reports in that regard there is no difference whatsoever.
For reference, I believe this has been the case since at least version 1.0, and that's just the oldest easily accessible video I found on the topic before testing it myself after some folks on the Discord were talking about it.