Optisan Viper, reticle focus ring makes reticle move?!

That is an unusual scope problem, Jonnes.

I don’t think I’ve ever heard of the Ocular Focus changing the perceived parallax before. I would put this down to a bad lens carrier / bad single unit.

As you’ll probably know Optisan make scopes for a very large number of retailers, retailers who can specify what lenses are fitted etc. but not the basic scope mechanicals (ie; thread pitch on screw-in parts, my only gripe with front AO scopes). It’s possible that those many retailers can specify certain options for their chosen lens mounts but as none of them make any sales pitch around the subject – who knows?

Optisan make excellent scopes, and have done for years – I’m sure your problem is down to one bad unit (Friday Afternoon Scope 😉 ).

In your shoes 🙂 I would go for a Replacement from Optisan.

I had a scope that came with my Umarex Octane do the same thing.  First off, springer has so much recoil that the scope came apart and then I noticed the whole reticle focus bell was moving.  The 3 locking screws had become loose and allowed the whole bell to rotate off.  It was when I rotated the bell to examine the insides of the scope that I noticed the reticle shift positions.  I would say either the screw path is not linear with the rest of the scope or the thread pitch is off on your focus ring just as BRS suggested because that was the only thing I could attribute to my reticle moving when removing my eyepiece bell.