Originally Posted by
dvd
I'm pretty sure the mod 60 had an annular groove at the bottom of the compression cylinder.
If the crud and remnants of old seals are not scraped out of the groove, the piston will not bottom out against the cylinder's end as it should, with the result that the piston's forward motion is braked by the gears rather than the piston coming to rest against the cylinder bottom. The gears and the whole system are not designed for this stress and will fail.
I have many different models of Diana GISS guns which I service myself and I never do up the gear covers so tight that I can not undo them by fingers when the gun is uncocked since if they tighten up and can't be turned easily while uncocked it means that the gears are loaded and it's time for new seals and shims.
The gears just synchronize the the two pistons and are idler gears, they should never be loaded at any time except during the cocking stroke.
HTH.
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