Cleaning cosmoline from a PU scope

[GunsNotPuns]

I bought a M91/30 sniper with PU scope and I'm faced with a challenge I haven't had before: Cleaning cosmoline from a scope.

Rifles are no problem, I've done it more than a few times, but I'm a little unsure how to proceed. I don't want to expose the scope to excessive moisture (I plan on using mineral spirits). The bulk of the cosmoline is located on the windage and elevation turrets.

Any tips and hints on how to do this with a minimum of fuss or potential damage?

 

[marc_j]

Don't use solvents because these will degrade the leather friction washer and will probably leak into the tube itself. Just wipe off the excess cosmoline with a dry cloth. If you remove the very small jam screw and the two larger dome head screws you will be able to clean the outer components of the reticle adjustment turrets. You can go further and remove the screws (2 each) you find underneath the knobs and this will expose the leather friction washers (often degraded) which prevent accidental movement of the reticle during firing. Remove the adjustment mechanisms one at a time - if you remove both at the same time it will be more difficult to re-assemble.

Take your time re-assembling the turret components - the trick is properly aligning the wave washer so the ID fits over the axis - if done incorrectly it will hang up and the turret will stand "proud" and the jam screw won't line up. Too much force = a money loser

If you are used to working with mechanics and small details, you can completely disassemble the scope for cleaning. Use optical grease to seal the screws, lenses etc. against moisture entry when you re-assemble. If you aren't too handy, leave well enough alone since there are small breakable parts and some steps in dis-assembly require some home made solutions.