I've had a few older scopes, mostly Weaver and Kahles, and sticking adjustment came up from time to time. I too give the turret area a few wee taps, an old habit I was taught way back in the 70's. When I buy a second hand scope of unknown history I now wind it all the way up and all the way down a couple of times, and I also count the clicks. Then I centre by turning back by half the total number of clicks. I bought a nice older Kahles a few months back that went cheap cos the seller was honest and said he couldn't get it to adjust properly. When I received it I gave it a few turns up and down, left and right and the whole thing just got easier and smoother. Mounted it and it works perfect, probably been on a rifle for the past 40 odd years and never touched.
Another issue I have sometimes found in the older scopes is you adjust for windage and it doesnt appear to change much, then you change for some elevation and the windage comes right. must be something to do with the mechanics as well.
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