I shoot a few barrels in the 16"-18" range on my TC Encore. Whatever load yields the highest velocity in the long barrel will yield the highest velocity in the shorter barrel. I have a 22" barreled .260 Remington Ruger M77 MkII and an 18" barreled MGM .260 Encore barrel. Oddly enough, they both have the same preferred load - 129 gr. Hornady Interlock with 44 gr. IMR 4350. The 22" barrel yields 2850 fps. The 18" barrel yields 2650 fps, as the 50 fps per 1" of reduced barrel length guideline would suggest.
