rc
all magic numbers aside, I think that is probably the best description I have ever heard, and certainly the most succint !
(magic numbers ETA imminent, no doubt, as always for this topic)
hint, there is no such thing as zero endshake, plus if it really really did "lock up like a bank vault", it wouldn't cycle, nor would you ever get the cylinder open again without a hammer. EXCESSIVE endshake is a problem.
I do have one target k-17 that is "tight" enough, that mere powder residue on cylinder face after ~100 rounds or so will yield cylinder drag you can feel... but a quickie wipedown and it's baby butt smooth, and always always "accuracy to be envied". You can see daylight if look close enough when clean, but scarce little. (Lost my .001/.002 feelers but it way less than .003. Color me happy with that.
me, I would stay away from endshake bushings, but not saying they won't work if done right. methinks that if there is that much weer on the gun, bushings really are just band-aids, and a more complete rebuild is preferable. Send it to factory.