As has been quoted over and over on this forum, and again. In this thread.
The powder which produces the highest velocity with a specified cartridge and bullet with a 26 (or 30) inch barrel will also produce the highest velocity in a 16 inch barrel.
A different, faster powder, might produce nearly as much velocity in a 16 inch barrel, with significantly less barrel pressure at bullet exit. Which can give less noise, recoil, and muzzle blast.
