I have a Ruger single six 22 I need a rear sight for it, It has a notch cut in the top of the receiver I bought one that you slide in from the side but it shoots way low at 10 yard's is there another option to put a higher one in the back If so where would I find on or do they make an adjustable on that fits in the notch the gun was built in the late 60's between 64 and 69