In my understanding of the code, the manual and auto big bertha are two different turrets. However, since they're acting as the same turret, I recommend disabling the placement dust poof animation when switching from manual to auto and auto to manual since the animation is only needed when a new turret is placed down.

Yeah, that's true, the manual Big Bertha is basically an Artillery with 0 auto range. I think it's a nice idea to turn off the dust.

I think it would be the best if you could just change the range on the fly. That could completely make the replacement process obsolete. However, I didn't find a way to do that.

Do you have an idea to disable the placement dust?

I do not. I'm new to lua and learning off your code. My best guess is it's a vanilla feature that you imported when creating Big Bertha. The simple logical solution is to make the manual and auto mode not require switching between two different objects, but you stated that that's not possible at this point. The next logical solution is to add in the option to remove the manual and auto feature so you never encounter the dust animation. However, that doesn't make much sense.

TL;DR I have no idea and it's a minor visual bug not worth trying to fix with our/your current knowledge.

Yeah. Unfortunately, the Factorio modding documentation has some gaps. It would be super helpful if you could get all attributes and methods of an object.
But I didn't find a way to do that.
Maybe in the future I will find a way.