What's wrong with leaf springs? Nightforce uses leaf springs made of titanium in all NXS scopes (not sure on the other lines, but I imagine they all have leaf springs). Other high end makes also do. Leupold does. Are coil springs inherently better? Why? hint: they aren't and present issues in scope design like limiting erector travel due to coil bind.
It's attention to detail and base design. Leupold has some reliable offerings, and some not as great ones. For a long while, no one called them out on it. Times have changed, but they are sluggish to improve.
The problem isn't that they don't know how to make a reliable optic. They choose not to for whatever reason.
Jeremy
I'm only five years late but no one seems to have answered Jeremy's question, so here goes ...
The main problem with leaf springs is that they can get twisted laterally when people mount their scopes carelessly. Then, under heavy recoil, they can break.
Even when the erector tube is perfectly centred, recoil can pull the front of it down and that will stress the spring laterally, too.
Part of what causes springs to get twisted is that they may hang up on the outer scope tube. To stop that happening, Nightforce tumbles some of its springs for days to get any burrs off.
These problems are likely worst in modern scopes because of the mass of the complicated erector tubes needed for high-multiple variables. Theoretically, they could break on the old reticle-movement scopes, too, but the mass able to move in them is a small fraction of an erector tube's, and I've never heard of it happening. The danger should be even less in the single-turret type if the spring is just pressed straight down by a reticle ring running in a dovetail
a la the old B. Nickel, Marburg.
Swarovski used a flat spring in the Z3, with a rounded tip to cut friction, but four helical springs behind the erector tube in their Z5 and Z6 scopes. Their publicity mentions forces 500 to 800 times that of the erector tube at rest but they don't explain exactly how. A casual reader might think the springs are to resist longitudinal inertia but they are really to maintain the erector tube's contact with the turret screws or at least to return it to battery after recoil inertia dislocates it.
Over time, however, I see those coil springs as aiding recoil in moving the erector tube forward in the scope, after which parallax will set in.
If I were making an image-moving scope (perish the thought!), I would use a strong coil spring in a third turret at 7.37, across from the turret screws. I'd top it with a brass washer and locate it with a screw to work something like the Burris Posi-Lock but stronger, to lock the erector tube in place after zeroing.
I'm sure most scope makers know conventional 'constantly centred reticles' make a dodgy concept but can't get off the merry-go-round. The Germans and Kahles hung back from it as long as possible (and Pecar never used it, even in their Champion models). A friend wrecked so many image-movement Leupolds on his 458 Lott and 505 Gibbs rifles that they made him a special one that has not succumbed, even after 1500 shots. My guess is they made it up from bits left over from the old M7 or Mountaineer models in 1964.
- 'Sam'