40 MB/s is pretty much the best you can get out of the 7260AC. The best result that I got with Intel N 7260 is 161.28 Mbps or 20.2 MB/s on a 300 Mbps connection. Here's the SpeedTest maximum throughput test for upload since the download speed is throttled by the university's ISP:
Running Win 8.1 Pro x64.
I installed Intel's Centrino Dual Band Wireless AC-7260 HMWG.
Windows recognized the AC-7260 and installed a driver dated March-2013.
Download speeds averaged 30.0 Mbps.
Then I downloaded Intel's most recent ProSet package for my OS (Wireless_16.7.0_e164).
from here: Download Center
This installed an updated driver with ProSet Tools.
New Driver Date 10/14/2013
Driver Version 220.127.116.11
Testing with an Ultra 4K Hobbit movie trailer:
My speeds now average 400.0 Mbps. (More than 10x improvement!)
This is slightly slower than Ultra 4K television, however.
Hopefully Intel will continue to refine the driver.