While target shooting at about 15 yards, my 27 seemed to be shooting at least 2 inches high. I know Glock has variable rear sights, and my sight has a "minus -" on the right side if that means anything. I have a tridium front sight that I'd like to keep on the gun now. I believe I need a lower rear sight, anyone have a factory low rear sight that they want to get rid of cheap for my testing purposes? Thanks alot!