Re: 308 Winchester barrel length
I've shot Varget powered 155-gr. bullets from a 32-inch .308 Win. barrel that left at 3150 fps with a normal maximum load. If the barrel was 40 inches long those bullets would probably have gone a lot faster.
Barrel length or contour doesn't seem to have any effect on accuracy, just muzzle velocity. Shorter ones are easier to handle and longer ones shoot faster. One advantage of having a longer barrel is when it's worn out, set it back three inches and start over with a virtual new, but shorter, barrel.