That will be wholly dependent on the AP power output, channel availability, and MOST importantly the Antenna you select (and then if you have non-standard length cables over 1m, etc then all the loss has to be factored in as well). Additionally, is this a PtP, PtMP, etc?
To be clear, there is no FIRM number. Below is a graph showing the 274 with the ANT-3x3-5712 out to 3km. You might find more success in using the Aruba 3D Outdoor Planner.
If you give us the range you are looking for, that may help, but 11ac and theoreticals pretty much go out the door once you are outdoors and we then rely on tested data to provide best practice numbers.