I pretty much go along with dfaugh. About every ten years or so, somebody goes to barrel chopping and checking the velocity.
Generally, it runs about 75 ft/sec/inch for cartridges with cases like the '06. Stuff like the .308 might lose around 50 ft/sec/inch. Magnums run closer to 100 ft/sec/inch.
Years ago, 26" was the standard for published velocities of factory ammo. With the advent of all the reloading component suppliers' data books, other lengths have become common. Still, the ft/sec/inch numbers hold reasonably true for horseback guesstimates.
Maximus, the twist rate is more a function of the ratio of length of bullet to its diameter. Longer bullets (heavier) need faster twists than short, light-weight bullets.
Lessee, what else? Faster burn-rate powders in short barrels mostly just reduce muzzle flash. A max load in a short barrel won't give any gain in velocity over the slow-burn powder in that barrel; just easier on the eyebones at night.
Drifting: One barrel-chop test of a 10" .44 Mag revolver started at around 1,600 ft/sec with 250-grain bullets. Down at one inch of barrel, the muzzle velocity was around 1,150 ft/sec. Out of curiosity, they removed the remaining piece of barrel and chronographed the last shot. Amazingly, it was right at 1,100 ft/sec. That certainly would make an interesting carry gun.