Do you mean sentry drones?
#Sentry gun range
main tusk
prime marten
No sentry turets, CONCORD
dire lichen
No sentry turets, CONCORD
A few of us thought it was 8k km. Others thought 10k km. A user tested and found it to be ~ 2.5k km (2,500km). I didn't see a screen recording of it, so take that as you will.
I'll try to find the link to the thread.
@prime marten you already asked this didn't you?