Good question jimmp. I'm looking forward to the replies.

Just peering into my SWFA scopes (objective end, with flashlight), I see the leaf spring screwed/pinned into place. On the 3-9x and 6x, there is one screw. On the 10x, I can see two screws. People claim that using a fastener to keep the leaf spring in place helps with zero retention, since the spring can't slip. If it slips, the erector tube moves and zero changes. Of course, the downside is more cost due to the extra machining, parts, and assembly time. Maybe a freckle more weight too?

On the Burris Fullfield, they are still using the big circular design that fits against the inner wall of the outer tube. I just looked at a new one the other day at the store. Supposedly this helps keep the spring in place, since the mounting area goes 360 degrees around the inner wall, instead of the typical narrow spring.

I've been told that Leupold used to have a leaf spring with barbs. The barbs were supposed to dig into the inner wall of the outer tube. The assembler would slip the leaf spring between the erector tube and outer tube. The spring tension and barbs would then hold the spring in place, without fasteners or glue. Maybe sandwiched between an inner ring. People have stated that the barbs could slip, allowing the spring to move, which can result in a change in zero.

I'm not sure if Leupold used this design, and if they did, if they still do. However, I've never observed any sort of fastener on the Leupold scopes I've looked into, but that doesn't mean that they don't do use something than can't be seen from the outside looking in.

My observations above are related to zero retention. In my simple brain, when I think about a scope "losing zero", I wonder about the leaf spring and how it is held into place. Maybe there is more to it than that, such as the amount of force pushing against erector, spring relaxation, etc.

For tracking, I don't know confused