Older 629-1 issue

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I have an older 629-1 I bought new back when (AVC35XX). I don't remember the exadt year it was purchased.

It's fairly high mileage. I carried it on duty for a considerable time and qualified twice a year with factory magnums. I also shot it a bazillion times with powder puff loads with Lee LCSWC's and also a considerable amount of Lee LCSWCGC's loaded fairly hot. End shake is good (I tightened it up a bit) and timing is pretty good.

The issue:
This developed shortly before I quit carrying it on duty. Under certain situations, discovered during rapid fire during qualifications, the cylinder will counter rotate during recoil or recoil recovery causing the hammer to drop on the previously fired chamber on the next trigger pull.

The issue can occasionally be replicated while dry firing by cycling the action double action while keeping very light counter rotation pressure on the cylinder. The cylinder stop can be observed to release and drop free of the cylinder notch momentarily as the trigger is being released after the hammer has dropped. At this brief fraction of a second the cylinder can counter rotate. This would be happening during recoil or recoil recovery in live fire. This can not be duplicated often but it can be duplicated if the action is cycled this way enough times.

I called S&W a couple of years ago and was preparing to send it to them for repair but they essentially told me I was just SOL and they couldn't fix it. I think it's related to issues they addressed with their magnum improvement program.

I'm thinking maybe I should try a new cylinder stop and spring.

Any other suggestions?

Thanks.
 
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New cylinder stop spring. A new stop certainly won't hurt either. Also check each notch in the cylinder for displaced metal. Any metal sightly raised on the back side can be gently tapped down with a small smooth face hammer. A small bump at the end of the lead in to a notch can cause the stop to bounce just before it should lock up and not fully enter the notch. If you find any here tap it back in place with a small punch with slightly rounded face.

Think how many times that stop has popped up into the notch and had the rotating cylinder slam into its side to stop it. Tap tap tap on the side of the notch bouncing back a bit into other side of it.

You are correct in that this bouncing out of lock up under hard recoil is the reason for the endurance package upgrade.
 
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Wolff springs has an extra power cylinder stop spring that can help in this situation, in addition to all of the above.

To peen back the metal around the cylinder stop notch, I like to use a polished flat ended punch on the flat side. Using the punch keeps the blows exactly where desired, and eliminates errant hammer dings.

Then I use a 5/16 steel dowel on it's side for the curved ramp side. The 5/16 size is the same curvature as the cutout.
 
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To add to the excellent info already provided, be sure to check the stop slots in the cylinder for impacted dirt and shooting debris......with a magnifier. Crud can be brushed out with a toothbrush (not your toothbrush).

Also, check to make sure the stop is "bottoming out" into the cylinder stop slots in the cylinder. If needed, there is an adjustment step on the top of the cylinder stop that allows material to be removed which will allow the stop to go deeper into the cylinder slots. (rise higher into the frame slot during final lock up phase) About .010" of let out is available if sufficient space is available between the bottom of the trigger hook and the stop bevel to accomodate.



 
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Thanks for the responses.

I'll look into the wolf spring.

The notches look pretty good. There is a tiny lip on a couple of notches but that's on the right hand side which logic tells me should actually help prevent the undesired rotation. But I'll go ahead and pull the cylinder and dress the notches a little.

There appears to be small shiny wear spots in the bottom of the notches that would indicate that the stop is bottoming in the notches but they could be old. I might take a hard stone to the adjustment pad and take off just enough to make it shiny. The top of the stop (ball) itself seems worn but I wouldn't know if it's lost enough metal over the years to amount to anything.

I'll pull the side plate off to look but what is it that causes the stop to drop a little all of the time just before the trigger is let back all of the way out? If I could address that by a thousandths or so that might do it too.

Again, thanks for the responses.
 
That is the trigger hook going back past the cylinder stop. It has to get back past it so it can hook it and pull it down again at beginning of trigger pull. But that should be just a small movement of the stop not all the way down unless you have a bunch of gunk or something in there

If you are letting the trigger bounce quite a bit in just right amount during recoil it could cause the problem. But as you are an experience big bore shooter, I doubt this unless you have lost hand strength.
 
My hand strength is good, although my knuckles do ache a fair bit. Plus this problem started about 15 years ago.

I'll order a new stop and spring and dress the notches and see what happens. I haven't pulled the stop. I'll wait until I get the replacement parts. I did pull the side plate.

From what I could see the adjustment pad is so small it's hard to see but of course it's still in the gun. I'm betting the new stop and spring will do the trick. It's not like it happens very often although it was annoying when it would happen during qualification but I generally had plenty of time to get them all off in time anyhow.

Thanks
 
Back in the day, "backspacing" of model 29's wasn't uncommon. Besides trying to wring out the last foot second of velocity, there were some mechanical issues involved.

Cylinder endplay was a biggie, I saw some startling endplay. As was yoke alignment and, as mentioned above, the cylinder stop and spring. The issue with the spring was often that whoever installed it wasn't careful to avoid kinking or having the spring not centered properly so it didn't drag on the stop while the stop was rotating. Making sure the hand fit properly also helped.

Hint: the end of the yoke barrel isn't always square. This can cause premature wear and increase of endplay.

Added comment: make sure you're keeping the trigger pinned all the way back during recoil and recovery. You should be able to let the trigger go forward as the gun is coming level.
 
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I can see how endshake could cause the gun to unlock, Rapid movement of cylinder under recoil causes stop notch to slide back and end of notch ramps stop down with enough momentum that the cylinder is unlocked just long enough to move out of battery.
 
You're better off with carbon steel for most of the lockworks parts. Stainless is too soft to hold up well in that application. I don't think they ever made any stainless cylinder stops. Maybe a few in the early M67 that had stainless sights. I know the SS mainsprings don't work worth a darn. They have an S stamped on them.
 
The one in there sure looks stainless. It's never been tempted to rust even where it shows wear. If it's plated it sure must be a thick plating. It's been rained on many, many times including through several hurricanes involving multi-day shifts. Of course even stainless can rust as my experience on the marine unit with my 686 proved but that involved serious salt exposure.

I did find this one but there doesn't appear to be an adjustment pad:

Stop_1.png


S&W Revolver Cylinder Stop | MIM Replacement | TK Custom | TK Custom Store
 
The TK manufactured cylinder stops are stainless steel. They are also 'oversize', which will mean they will require fitting. TK advised me via a recent e-mail that the ball on their aftermarket stops is .101". Factory OEM stops are .094" - .095".

Interesting quote from the TK website. Love the statement about MIM cylinder stop breakage. Quite a sales pitch.

"Designed to replace the standard MIM cylinder stop, this upgraded Steel cylinder stop offers exceptional cylinder lock-up and is guaranteed to last far longer than the stock cylinder stops. MIM cylinder stops break, it's not if, it's when. You'll be surprised how much difference a new part can make especially when it comes to reliability."
 
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