I've noticed on my rifle the rear sight elevation adjustment knob will only turn a fewartial turns before downward force on the sight itself is required before it will turn completely in the direction I want it to go. I've tried break-free and WD-40 in an attempt to loosen it up, but it doesn't do it. It's not a war-stopper as I can still adjust the sight, but my expectation is to be able to turn the elevation knob from one end of the adjustment range completely to the other without having to manually apply pressure to the sight itself. Thoughts?