I managed to get out to the range this afternoon after work, and put 50 rounds through the old 3" M10 I purchased a couple of weeks ago. This is the first time I've managed to get that much shooting done since I got it. 158-grain lead SWC pushed by a middling charge of American Select -- not a hot load by any standard. Upon removing the cylinder for cleaning, I noticed bright lead on one side of two of the chambers 180 degrees apart. Does this mean the cylinder timing is off for those two chambers? Is this bad enough to indicate I shouldn't shoot the gun until corrected? Lastly, is this an expensive problem, and should I seek a revolver specialist? Thanks!

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I think it merits a trip to a gunsmith. While I don't think it's a safety issue at present it is an indicator that something is going a bit out of spec.

I have a hunch that a gunsmith who is fully competent with revolvers is about as common as an aircraft mechanic who is fully competent with radial engines. I'll start looking around; any recommendations in western Wisconsin would be appreciated.

Atomized lead and powder deposits in that area would be considered normal. If the face of the cylinder shows signs of contact (rubbing during rotation) with the barrel extension during firing, then your barrel/cylinder gap is likely too small.

You can easily check the gap with feeler gauges, after thoroughly cleaning the cylinder face. Ideally, the gap should be .004" - .006". If it's too small, and there is adequate end shake, shims can be used to move the cylinder back on the yoke, and increase the B/C gap to an "in spec" distance, without having to remove material from the barrel.

Timing or "carry up", can be checked by slowly cocking the revolver in single action. The cylinder should lock into place on the cylinder stop when, or slightly before, the hammer completes it's rearward motion back to the cocking notch, and is standing on the trigger bevel. Check this after a thorough cleaning, and after safety checking to see that the cylinder is empty. Empty shell casings or snap caps can also be used to hold the extractor firmly in place, and eliminate any movement between the extractor and the cylinder during the testing and evaluation.

(edit) Add on: another thing to consider is the barrel extension on these revolvers is not finish cut with a pull through, piloted facing cutter.....they are (or were) cut, when necessary, by hand with a file by the fitter. As you can imagine, the consistency of the resulting surface can vary greatly, depending on the skill level of the person using the tool. This results in barrel/cylinder gaps that are all over the place..... 002" clearance on one side and .008" on the other.
This can cause all kinds of problems, particularly when there is some runout expected/allowed in the cylinder assembly, and additional tolerances allowed in terms of the OAL of the cylinder itself.

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Ret. LE, FA Instr, S&W Armorer

Give the gun a good clean & lube , then another range trip .
Make sure each chamber is fully indexed and in line before firing .
I would test it SA first . Next test it DA ... this is more than likely where the chamber doesn't fully index . Happens with wear ...wish you were in Louisiana ... Clark Custom Guns is a long way from WI .
I have an old Colt Police Positive Special with this problem ... one day I need to see if they can fix it for me .
Cleaning and lube might help ...worth a try .
Gary

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NRA Member

I have found that when I have undersize cylinder throats , this can happen . After opening them up , it went away . Your situation might be different . Try pushing a bullet through them . Can you push it through , or not ? Regards Paul

Hey Gary -- the cylinder locks up good and tight for each chamber. I'm not going to worry too much about it. It fires reliably and puts the bullets on the paper as it should. With Wolff replacement springs installed, the trigger is smooth as can be.
I've used Clark's 10/22 trigger parts and found them to be the best aftermarket trigger for that little rifle. As it happens, I have family in St. Bernard parish and nearby in south Louisiana. Good excuse for a visit. and, oh yeah, uh, the food is pretty good down there, too. Thanks!

I copied your answer into my compendium of firearms wisdom -- thank you for sharing your knowledge and experience!

It may take a quicker burning powder or higher pressure load to get the bullets to obturate, "bump up", and seal the barrel. It looks like lead from gasses getting past the bullet.

yeah i think that is the issue easy fix with a reamer.

Plated bullets aren't much more.

Don’t trust just anyone to touch that. Not all gun smiths are forensic gun smiths with the ability to correct a pistol.