I picked up a low rise optic mount from Czechpoint for my 58. I went to install on side receiver rail and noticed it was very loose. Instructions say to compress spring to release that little tab from bottom of nut to clamp. Then I should be able to turn nut to tighten. Well problem is I cant turn the nut at all. I got finger cramps from trying to turn the nut. Any ideas? Would be much appreciated. Thanks