Excellent advice.It will work without an aperture. The 81 DL with the model 12R sight was my first rifle. (I was 8 years old when it became "mine") It was also my first peep sight. With it I hunted squirrels, gophers, grouse, skunks, badgers etc etc. I had it for many years before I realized the aperture was missing. (Its still missing) I shot it as a "Ghost Ring" long before the term "Ghost Ring" was trendy. It was amazingly accurate! Remember, forget about the rear sight when shooting a peep. Just look through it. Your eye will automatically center the front sight. If you are going to be target shooting for ultimate precision, then yes, use a smaller aperture. It will clarify the front sight better due to the increased depth of field.