The large rear peep sight hole is the reason Type 99 rifles do not shoot as well as they are capable off . It is really too hard to get the exact same sight picture 5 times in a row. It is like playing pin the tail on the donkey with a 6 foot circle compared to a 6 inch circle , a lot harder to get the exact center time after time . If you put a clip on cover with a smaller peep hole over the rear sight your groups will really shrink .