629 Cylinder Locks Up After a Few Rounds - Pistolsmith
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Old 10-14-2013, 08:00 AM   #1
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Join Date: May 2012
Location: Georgia
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629 Cylinder Locks Up After a Few Rounds

Hi Guys,
After years of searching, I finally found an older model 629 (no dash) pinned barrel, recessed cylinder, 8 3/8 inch revolver in very good condition. This pistol does not appear to have ever been worked on before. When I first purchased the pistol, I noticed the cylinder would not turn freely when swung out from the frame. The cylinder would bind up as it was being rotated, however, only in one spot. No problem, I removed the cylinder from the pistol, unscrewed the ejector rod from the ejector, removed the springs and pin, screwed the ejector rod back into the ejector, placed it between centers on the lathe and using a dial indicator, straightened the ejector rod. I then cleaned the parts thoroughly, sparingly lubricated the parts and reassembled. Problem resolved. I went to the range and fired about 20 rounds through the pistol (reloads with 245 grain cast bullets) then the cylinder became difficult to rotate while closed, almost to the point of locking up the pistol. Took the pistol home and found there was debris under the ejector preventing it from closing flush with the cylinder. I cleaned the cylinder thoroughly paying close attention to the area under the ejector. Next trip to the range and exact same problem occurred. Brought the pistol home and found more debris under the ejector. This time I removed the cylinder and unscrewed the ejector rod for a closer examination. Under a magnifying glass, I found the machined area of the cylinder where the ejector fits to be very poorly machined. The area was very rough and there where even burrs remaining in some of the corners near the "points of the star". The ejector was almost as poorly machined. There are also gaps between the "points of the star" and the recesses in the cylinder.

I also have a 629-1 (non-pinned or recessed, with non-N prefix serial number) with 6 inch barrel and have never had any problems with it.

I have a couple of questions:
1. Has anyone else experienced a similar problem? If so, what did you do to correct the problem?
2. What should the gap be between the ejector and frame with the cylinder closed?

Thanks,
Bill Austin
 
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Old 10-14-2013, 04:59 PM   #2
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Join Date: Jun 2001
Posts: 1,800
Getting burned powder and other debris trapped under the ejector is a common problem with DA revolvers.
The "fix" is to hold the muzzle upright as you eject the empties so any grit or burned powder falls free instead of getting trapped.
When cleaning, use a brass "toothbrush" to liberally scrub the cylinder recess and the underside of the ejector.
Grit can get trapped and when the gun is fired it can actually embed into the steel.
This can be virtually impossible to see and normal cleaning may not get it all.

Gap between the ejector and the ejector seat in the frame is a matter of what's known as "Cylinder end shake" and head space.
End shake how much back and forth movement there is of the closed cylinder in the frame.
Head space is checked with head space gauges.

You want minimal end shake, but there has to be some or the cylinder won't rotate.
To measure:
Thoroughly clean the ejector, it's seat in the cylinder, and the frame face.
Push the closed cylinder to the rear and hold it there while you measure the barrel-cylinder gap with an automotive feeler gage. (This is also the true barrel-cylinder gap).
Then push the cylinder forward and hold it there while you gage the barrel-cylinder gap again.
Subtract the one measurement from the other and that's how much end shake is present.

The most common issue is that there's too MUCH end shake.
You have too much end shake in a S&W when it get over about 0.006".
If you thoroughly clean the underside of the ejector and it's seat in the cylinder, and the front of the frames ejector seat, then close it and measure as above, almost undetectable end shake to 0.001" is about perfect as long as the cylinder rotates freely and without any binding.

Again, it's almost unheard of to have too little end shake UNLESS, someone tried to install a new cylinder by just "dropping it in".
Cylinders are THE most fitted and adjusted revolver part and these are extensively fitted and adjusted at the factory.
Having a replacement cylinder, new or used not fit properly is common. They have to be fitted to the individual frame.
So, if this was not bought new by you, and you have insufficient end shake, look for a Billy Bob attempt to install a different cylinder assembly.

The rough cylinder ejector seat is a possible indication someone switched cylinders to get a better cylinder.

The fix for your gun would depend on the actual problem if you have too little end shake, but head space is good.
It may require machining the rear face of the ejector, or trimming the yoke barrel.
Machining the ejector face is what's done at the factory to set head space, so you don't change that without a set of head space gauges, and knowing what you're doing.
Simply trimming the yoke barrel without being absolutely certain that's the problem is how you ruin a nice gun.

My advice is to check the cylinder end shake as above, and if it's in spec, just make sure to hold the muzzle up while ejecting and always scrub the ejector and cylinder often.

As for having a cylinder with a rough ejector seat, that's also not common.
True, at times past there were some bad things come out of the factory during the Banger Punta, and Lier Siegler days.

If the cylinder is really rough, you might well benefit in sending the gun in to S&W for a new cylinder.
I doubt they will install a new one for free, but as an obvious factory defect, they might.
 
Old 10-15-2013, 01:14 PM   #3
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Join Date: May 2012
Location: Georgia
Posts: 2
dfariswheel,
Thanks for the very detailed response. I've made the checks that you recommended tonight and here's what I have found. First of all, I made all of these measurements with 6 empty unsized cases in the cylinder that had been fired in this revolver. The End Shake is 0.002 inch taken using the method described above. With the fired cases in the cylinder, the barrel cylinder gap decreases to 0.003 inch. The headspace measures 0.011 inch.

I believe I need to square up and trim 0.002 inch off the end of the barrel, then square up the yoke barrel while only removing about 0.001 inch from it.

Regarding S&W quality, I've got two model 29's that I purchased in 1974 (6.5 inch) and 1976 (8 3/8 inch) that are machined extremely well. Everything fits as it should and the 6.5 inch has functioned properly and has never given me one bit of trouble. Never fired the 8 3/8 inch, but its quality is every bit as good as the 6.5 inch. On the other hand, two of the four stainless steel S&W revolvers that I have owned have had some type of issue that required to be corrected.

Last edited by Bill Austin; 10-15-2013 at 03:27 PM.
 
 
Old 10-15-2013, 04:52 PM   #4
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Join Date: Jun 2001
Posts: 1,800
The correct way to measure end shake is with the chambers EMPTY.
Loading the chambers with cases gives a false reading.

Do not trim the yoke barrel, you already have 0.002" end shake, if anything you want LESS.
If you want to do anything, drop in a greased end shake washer.
You can buy hardened stainless steel end shake washers from Brownell's.
I'd put in a 0.001" washer.
If you lightly trim the yoke barrel to insure it's perfectly square, use a cutter with a pilot to insure it is perfectly square, then put in two greased washers.

This will bring end shake down to about 0", but make sure the cylinder doesn't bind.

With the end shake gone, your cylinder will be moved back where it should be and your barrel-cylinder gap should be close to a perfect 0.005".

As for the binding you had due to fouling under the ejector, just hold the muzzle up when ejecting empties and keep the areas clean.
 
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