Cleaning a air rifle(daisy powerline 880)?

so i read a little bit about cleaning the barrel and people say you dont have ot do that. but i stuck a bit of tissue in the barrel and it was covered 50% in black stuff. i shot some lead pellets in it is that what the black stuff is and i noticed that some shots go wildly off couse when i shoot. so should i clean out the barrel or is it ok with the black stuff and if i should clean it what should i use