If it were me, I would look into a 7-08,.260 Rem, or creed as said above. 270 Win is my favorite cartridge, but you will get the same performance out of a short action cartridge and 20" barrel.
I love the .270. If you just want that cartridge with a short barrel, go ahead. It will kill stuff.
I don't think a 270 needs a longer barrel than a 260 or 7mm-08. Whatever the performance difference between a 24" 270 and 24" 260 will be pretty much the same as between a 20" 270 and 20" 260.
