Yesterday, I looked at a Model 66-1 (4" barrel) that had been posted for sale on a local forum. The owner was out of town and will not return until next week, but he told me to go by his office and his secretary would get it and let me inspect it. The first thing I noticed was that the cylinder was difficult to open. However it eventually did open, without me forcing it. I am unsure what angle (slightly up or slightly down, or generally straight) I had the pistol pointed when it did open. I did notice the thumbpiece seemed a little loose, but with it not being my revolver (yet?) I was not about to try to tighten it. I knew I needed a lot more education on this, and upon returning, read numerous threads on sticky cylinders, extractor rods, center pins, loose thumbpieces, etc. If I had known some of the things I know now, I would have looked more carefully, and taken some pictures.

I went back and looked at the photos on the ad in the local forum. One photo shows the cylinder open, and the breechface (?), with the locking (?) bolt apparently protruding, maybe an eighth of a 1/8 - 3/16 of an inch, +/-. This did not seem right to me, so I checked my revolvers (all S&W) and the bolts were flush with the breechface with the cylinders open (the cylinders all open normally). The photos with the ad are decent, but I cannot be absolutely sure the bolt is protruding - although it sure appears to be the case. This did not make an lasting impression when I was examining the revolver - I wish I could have read up on sticky cylinders before looking at it.

The revolver seemed to cycle well, had minimal flame cutting, with no evidence of significant forcing cone erosion.

I know how to check some things, but am nowhere near to being a "smith", and hopefully would never use anyone but a gunsmith to take the sideplate off. When the talk turns to hands, ratchets, and pawls, bolts, etc., I am somewhat ignorant.

Would a loose thumbpiece cause the issue with the bolt (if there is one)? Will tightening the thumbpiece help? Should I be greatly concerned, and could I be looking at an expensive fix if I purchased the revolver?

I hope I have used the correct nomenclature in this post.

I would appreciate the thoughts of those far more knowledgeable than myself.

The most common cause of a cylinder being hard to open is the ejector rod being loose, check it for tightness and also check to make sure there is some gap between the end of the rod and the locating lock on the barrel.
Of course the pin/plunger for this lock goes in the end but there should be a gap all around that.
A loose thumb latch is extremely unlikely to be the problem.

OK, the locking bolt is the little widget in the barrel underlug that engages the end of the ejector/extractor rod when the cylinder is closed. The item in the breech face is the bolt.

It is possible that the ejector/extractor rod is slightly loose and easily fixed. It's not unusual to find cases where the center pin isn't long enough to press the locking bolt clear of the end of the ejector/extractor rod. You can determine this by pressing and holding the center pin flush with the ratchet and seeing if the center pin is either flush with on very slightly longer (0.005 in) than the ejector rod. It's also possible that the locking bolt isn't quite right, there's supposed to be a slight flat on the end that engages the ejector/extractor rod, not a knife edge.

It's possible that the ejector/extractor rod wasn't properly fitted originally or the locking bolt isn't quite right and some idiot decided to correct it by futzing with the bolt. It's also possible that the bolt wasn't properly fitted at the factory and someone decided to "fix it".

I'd check the center pin length, tighten the thumb piece nut and see if the bolt is now flush, or very slightly (0.005 inch) proud of the breech face/recoil shield with the cylinder open and the cylinder opens easily. If it sticks out as far as you estimate-which I kinda doubt-there's something seriously wrong. The thumb piece should, with the cylinder closed, have a very slight rearward movement to make sure the bolt isn't binding the center pin.

Without actually seeing it, it's hard to make a clear diagnosis. Revolvers really aren't simple mechanisms, there's a lot of little things that have to be right. Armorers/revolver smiths who know what they're about don't grow on trees.If there's no ruined parts, just some minor adjustments needed, you're probably looking at about $50.

What you might try, is to offer to buy it, but due to the problems, it's gotta go back to the factory for repair. You'll pay for the repairs but the repairs come off the price. Or, he pays for the repairs and you'll pay his original price.

[FWIW, while it doesn't help you, when I go looking at used revolvers, I take tools and gauges and check all manner of things like barrel/cylinder gap, end play, headspace/rear gage, carryup, barrel/chamber alignment and yoke alignment before I'm prepared to make an offer. Yes, that does tend to intimidate the seller but I know exactly what I'm buying.]