One jokes about the use of "olive oil" as a patch lube, BUT! In the very distant past olive oil as a muzzle loading lube was referred to as "sweet oil" and was until not too long ago a LOST PIECE OF INFO. Cleaning an old barrel, or starting with a NEW barrel, one can permanently SEASON a barrel with "olive oil aka sweet oil", and will notice that once done, the barrel will be permanently MANY TIMES EASIER TO CLEAN, and foul not as quickly. It is something our ancestors already knew, and was lost along the way perhaps when smokeless powder came along.
To season a new or old barrel one has only to make sure it is completely stripped inside, and then fired 10 to 15 times using patches soaked in "olive oil, aka sweet oil". This will season the barrel, and accuracy will last longer with less cleaning in between shots.