you can take the breech plug out with a powder charge and bullet in the gun,just make sure you an't smoke'n cigs when you pour the powder out.When i set my scope it is with a clean barrel,then after i get it set with the clean barrel (this wll take many shots from a clean barrel to get it perfect) i shoot it three or four times without doing any cleaning to see how the second ,third and fourth bullet fly.Then you clean it throughly and do it again till you know your gun .Untill you do this you are only guessing your shots with a dirty barrel.