I recently bought a used buckmark 5.5 target. It came with a reflex sight on it which i would like to remove and replace with the factory iron sights so that i can carry holstered while hiking. I have the iron sights however, i am missing the screw ( or what ever it is that fastens the rear sight to the rail) that mounts underneath rear sight. I have ordered what i thought was the right screw a couple different times from midway but they didnt worked. any ideas?