I have 20, 22, and 24. The 24 is perfect, but 22 works very well, not much MV loss, a much lighter rifle, especially with just its iron sights zeroed at 200 yards.
The smaller bore on a .30-06 size case means slower powders work best, but no law says you have to make every bullet run at maximum velocity. Even a powder like 4350 will push a 130-gr out of my 20-inch Mannlicher at 2,950 fps, with a normal load. Muzzle blast is noticeably greater on a 20-inch than on a 24-inch barrel.