A typical reload that gets 2835 ft/sec with a 139 gr bullet out of a 24" barrel will get about 2640 ft/sec from a 16.5" barrel.
http://shootersnotes.com/calculator/velocity-estimator/
You can also find loads for the 7mm - 08 at
http://ammoguide.com/?catid=15 and calculate the velocity for the new barrel length by selecting the "velocity estimator" button above the load details.