Remington does the SPS AAC in a 16.5, in both 308, 223, and I believe 300 Blkt. They also make the 7615P pump with a 16.5" if you can find one for sale Mossberg builds the Scout in 16.5. I believe the Patrol is also also a 16.5". The Troy PAR has a 16.5 in all configurations/calibers. Ruger Gunsite Scout comes with both an 18", and a 16.5", depending in which one you get. Thompson Center builds barrels for their rifles down to 15", if you can find/order one.
This is just a quick list off the top of my head. There are lots out there