I just picked up a used 10-7 4" in nickel. I've noticed that the cylinder won't open when one particular chamber is in the firing position. The cylinder opens normally when any of the other 5 are in the firing position. I've checked the ejector rod and made sure it's tight. Lock-up is tight and end shake seems minimal. What else should I check?

I would check for run out on the extractor rod. If the rod is not concentric when the cylinder turns, the rod can bind at the interface between the end of the rod and the front locking bolt.

Also check that the end of the extractor rod is free of burrs, and that it is flat (90 degrees) at the end. Sometimes when the end of the extractor rod is fit (filed) the intervention can render the opening at the end of the rod either rough, or the rod itself not perfectly flat on the end. (or both)

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Ret. LE, FA Instr, S&W Armorer

I had one with a bent extractor rod.. made opening difficult..

Bent yoke from flick of the wrist cylinder closings?

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NEVER GIVE UP YOUR GUN

I checked the ejector rod and it has no visible runout. I removed and inspected the cylinder and it seems ok. It feels as though the binding is in the ejector "star" area, but I'm not 100%.

Can you see a defined line in the pocket below the breech face where the lugs on the extractor would rub if that's the cause.

Here's a picture of the breech face. I don't see any evidence of the extractor rubbing. I also looked at the gap between the cylinder and the forcing cone. The cylinder isn't making contact at all and the gap appears consistent on all 6.

Attached Images

10-7.jpg (50.4 KB, 75 views)

This is a wild guess at your problem but it happened to one of my guns.
I had a 15-2 I bought used that would lock up seemingly at random. The cylinder would not turn even when trying to cock it with the hammer. The front of the cylinder would be dragging on the barrel. You could force the cylinder open with your fingers but just barely. The ejector rod was tight and all was fine under the side cover and no burned powder under the ejector star. The odd thing was that the problem would come and go with no predictability.
Long story short, I detail striped the cylinder and found a wad of hard carbon like material in the ejector rod channel. I guess that crud would move around and somehow stop things from working. After cleaning the cylinder the gun now works just fine.
Like I said this may not be your problem but it may be worth checking out.

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"I gots to know"

Thanks for the recommendation to thoroughly strip and clean the cylinder. I think it may have led me to the issue. I took the cylinder completely apart and cleaned it and the problem actually got a little worse. It's starting to look like the extractor rod isn't pushing the locking bolt (under the barrel) far enough forward for the cylinder to release. Before I disassembled and cleaned everything, the ejector rod was screwed on VERY tight. When I reassembled, I didn't tighten it as much, and the problem seems to affect 3 or 4 cylinders now rather than just one. Is there a way to adjust this?

The center pin should come flush with the end or just slightly (.006" - .008") above the end of the extractor rod when the thumbpiece is pushed fully forward.
If the center pin is short, a small amount of material can be removed from the end of the extractor rod. As previously indicated, make sure the end of the rod is kept free from burrs and is flat.

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Ret. LE, FA Instr, S&W Armorer

I believe shortening the extractor rod will solve the issue. Does shortening it involve a lathe? I suppose I can buy a replacement rod to experiment with.

Please take it to a gunsmith for peace of mind and a properly functioning weapon. It's a gun, your life may depend on it.

Kaaskop49
Shield #5103

A good file and steady hand will do the trick. Just a pass or two then try operation.

Slow and steady. Recheck often.

With the cylinder swung out, I pressed the center pin (to simulate actuating the thumb piece). At full depression, the center pin was recessed roughly 1/32 (maybe slightly more) below the end of the ejector rod. I'm thinking that's WAY too much to shorten the rod. I ordered a new center pin and ejector rod so that I can compare them to the current ones and then make a decision on how to proceed.

Remember to also check for excessive end shake on the cylinder, misalignment of the yoke, and shooting debris inside the cylinder assy....especially under the the extractor itself, as these problems can also contribute to the issue with the center pin/extractor rod/front locking bolt interface.

If you are unfamiliar with the proper fitting of the parts you have ordered, I would agree with the previous posts concerning an evaluation and/or repair by a trusted competant gunsmith.

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Ret. LE, FA Instr, S&W Armorer

Thanks armorer. I've stripped and cleaned the cylinder, so I'm sure there isn't any gunk fouling the operation. I thought that the extractor (star) was the only fitted part. If the ejector rod and/or center pin need fitting, I'll be visiting a gunsmith.

Just to follow-up. I received the parts yesterday. Changed out the ejector rod and everything works perfectly.