I've been reading the LongRangeHunting forum for a couple of years now and find the information quite helpful. I've even seen reference to the topic I will discuss here today. That is, the stiff focus knob on Sightron scopes.
I'm on the high side of your long range hunting age poll and have hunted all my life. I have shot a number of big game animals at ranges to near 800 yards (most of them in the 400-500 yard range), but have always carried a range table and used hold-over to complete the shot. Since this is not as precise as I would like, I decided to purchase a good scope and ballistic calculating rangefinder.
After a great amount of investigation, I decided on the G7 rangefinder as a "complete" tool for the ballistics calculations. And, I decided on a Sightron 8-24LRMOA scope for my favorite long range rifle (a pre-64 Winchester action mated to a Hart barrel and chambered for the 7mm Mashburn Super Magnum).
In testing this combination my only issue has been the stiffness of the Sightron scope focus adjustment. My hands are rather arthritic so it is quite painful to adjust the focus knob when it is warm and I can't even imagine doing it when I'm on the mountain and it is cold.
So, I came up with a rather simple solution. It involves using a 31.8mm (1.25 inch) diameter bicycle seat clamp ring with the clamp bolt removed (see photograph). The photograph shows a clamp ring with the bolt removed installed on the focus knob as well as a complete clamp ring with its bolt laying by the rifle. The focus ring measures very close to 1.25 inches in diameter and squeezing the clamp in a vise will make it fit snugly on the the focus ring. This increases the focus ring diameter and provides a couple of "push/pull" points so that the focus now adjusts easily with my arthritic hands.
The Sightron scopes are my favorite. I have 3 Sightrons with the last one having the MOA reticle on an SIII 8-32 x56. Personally i prefer the front adjust like on the SII Big Sky over the rear adjust on the SIIIs. I also find it very stiff and hard to turn.