IMO this is a tougher question than at first it might seem.

Yes, a 24 inch bbl will get you super velocity, but the answer really depends in my opinion on what you are planning to use the rifle for.

Here is a caliber that like the 6.5 Swede is truly useful and superb in barrels from 17 inches on up.

Where some cartridges might shovel lots of unburnt powder out the hole end if the barrel is too short, the 7x57 {and 6.5 Swede, .308 Win, .300 Savage, etc} are winners with stubby's too.