Backlash in scope (follow-up question to a 2012 thread)

[gdbleb]

I'm calibrating scopes on two 22LRs that have "good" 4X scopes from the 1980's. Leupold & Nikon ( ~250-300 IIRC).
They both performed quite well on box test of 5" (10 MOA) at 50 yards.
However on one scope at the very beginning of shooting the POI did not change after a small adjustment. The second shot was perfectly placed and I noted a "sticky scope adjustment". Subsequent adjustments were right on.

I found this excellent post in the archive from 2012 with Boyd's advice on backlash -
https://forum.accurateshooter.com/threads/twisting-turrets-backlash.3800540/#post-37544724

My question is if my scopes move the POI down on a clockwise turn of the elevation screw, is this actually raising the erector tube? And if so the spring in there would be pushing down against gravity. Correct?

Obviously, these scopes have been sitting for decades and get taken out only a couple times a year.

Many thanks for this valuable archive.
Dean

 

[boltfluter]

If I am understanding your question, the turret is pushing against the opposing spring. Your erector tube thinking is correct.

Paul

 

[BoydAllen]

As you look at the scope from the back, the bias spring is typically 45 degrees below the horizontal on the left, on the opposite side from the windage knob. I believe that turrets generally have RH threads, which means that when your rotate them clockwise you are pushing the erector tube against the resistance of the bias spring, the spring that holds the erector tube against the inside ends of the turrets that contact it. That is all you really need to know. Turrets are really just fine threaded jacking screws with clicks and scales. When you turn one of the knobs counterclockwise you are depending on the spring to overcome all of the friction at the erector tube pivot, the sliding of the spring on the erector tube and the ends of the turrets on the erector tube. Sometimes it doesn't until the system is jarred. That is why you are safer to finish all adjustments turning the turrets clockwise which in some cases involves going past your intended setting and coming back to it. I generally go past by an MOA or so. Some scopes have two bias springs, each opposite one of the turrets. Some have coil springs with plungers instead of leaf springs. These are usually where a single leaf spring would contact the erector tube. I think that you are overthinking this.

 

[gdbleb]

Paul & Boyd, Thank you very much for your responses.
I'll finish all adjustments clockwise per your recommendation.