Oil in the barrel? I am one that does oil his barrel. After a day of shooting, I use the hot water method for cleaning my rifle. After I have the barrel clean, I run a few patches of Hoppies #9 through it, then some clean dry patches. If this rifle is going to be stored, then I run a light coat of Rem Oil down the barrel and store the rifle muzzle end down on a piece of cotton cloth.
I do essentially the same thing, but recently have been using Birchwood Casey Sheath as a bore preservative (used Break-Free prreviously). Sheath dries in the bore, and makes it much easier to load the gun later. It only takes one dry patch and two popped caps before loading when using it.
To help eliminate confussion, oil in the barrel should be used when storing the firearm. When you intend on shooting that firearm you should remove the oil to eliminate excess pressure which can cause POI shift, be dangerous and damaging to the firearm.
IT IS ABSOLUTELUY ESSENTIAL to get
ALL OIL out of a muzzleloader barrel before loading it! Oil will kill powder AND caps!!