This is the long and short of it: hunters spend too much time worrying about barrel length.
It doesn’t amount to that much. Really.
Yes, longer barrels do increase velocity of most loads … at least a bit. It’s generally between 25- and 50-fps gain per inch of barrel added; the same is typically lost per inch of barrel cut off. Factory ammunition and most handloads will vary that much in velocity from the same barrel.
More important than fussing over an inch or 4 of barrel should be fussing over consistent ammo and plain-old accuracy. Combine that with a solid knowledge of your particular load’s trajectory curve and you’re good to go.
I know this because I’ve lived it. For years, you wouldn’t catch me dead with a velocity-robbing 18-inch barrel, and rarely a 20-incher. But one year I wanted to hunt mountain goats with a rifle that wouldn’t beat me up before I reached the goats. So, I took the lightest I could find—a Kifaru Rambling Rifle chambered in 7mm-08 Rem. with an 18.5-inch barrel. The whole darned rifle weighed less than 4 pounds naked. Fully scoped and rigged, it didn’t break 5 pounds. But it shot. So I memorized its trajectory, went hunting, made it up and over several mountains (some of which I needed to use my teeth to cling to) and hit my big mountain goat from 350 yards away, first shot. Later, I punched a spectacular caribou bull from 125 yards away. You don’t always have to shoot far in the mountains.
I still like maximum ballistic efficiency from some rifles, so when buying or building one to be used for long-range shooting in open country, I will choose barrels 24, 26 and even 28 inches long, but I don’t plan to hunt through timber or up steep mountains with them.