Well, you're going to need a carbide bit to do the drilling. Chrome is hard stuff and you'll ruin a HSS bit trying to punch through the chrome plate.
118 degree bits are fine. You'll want to center drill the hole to prevent the twist drill bit from wandering off either side of the barrel.
Usually, I drill the hole under-sized by about .005 and then follow up with a chucking reamer to the desired size. This gets rid of any burr on the interior of the barrel.