yes I did a 3-9x half mild dot size 40objective I think I got from for 40-50quid second hand
was a bit tight to release the locking ring, I think I was not only turning the outer ring but had to use a plate to turn the inner ring with the 2 slots...

if you unlock it turn out the cylinder where the front lens is in, then while holding that bit wind the outer locking ring back in. may take a few turns to get there since while winding in it may rotate the lens too.
can go very lo distance at max magnification, but of course it will get blurry at far distance. but it is more about minimizing parallax error rig


still too few genuine airgun scopes out there!