19-4 Cylinder Hard to Open on One Chamber Only

[scruffy]

Why would the cylinder be difficult to open on my Model 19-4 on one chamber only? Pressing the cylinder latch forward and 5 of the 6 chambers and the cylinder will open easily as normal. On one chamber only (same one each time), I have to use a lot more force than should be required. The revolver is in very good condition and has less than 200 rounds through it total.

Things I've checked: The chamber in question has .004" B/C gap (as do all chambers) and zero end play. Ejector rod is tight. Extractor star is clean on top and underneath. Bolt is clean and just a hair below flush with the recoil shield, no burrs or peening, front tip of extractor rod moves forward freely as does the pin in the barrel lug. Both are clean, lubed and undamaged.

I'm stumped. Any suggestions are welcome before I take it to my local gunsmith. Thanks.

 

[armorer951]

I would guess it's due to runout on the extractor rod. This runout can build to a point on the front locking lug on one or two chambers, and then drop off dramatically on the following chambers.

This can also be exacerbated by a non-concentric hole and inside taper (if there is one) in the end of the extractor rod.

Another variable is if the tip end of the extractor rod and the flat on the rear surface of the front locking bolt are not cut exactly 90°. (they rarely are.)

Last but not least, small burrs.

 

[scruffy]

I would guess it's due to runout on the extractor rod. This runout can build to a point on the front locking lug on one or two chambers, and then drop off dramatically on the following chambers.

This can also be exacerbated by a non-concentric hole and inside taper (if there is one) in the end of the extractor rod.

Another variable is if the tip end of the extractor rod and the flat on the rear surface of the front locking bolt are not cut exactly 90°. (they rarely are.)

Thanks, I appreciate it. I forgot to mention I checked carefully for runout and zero wobble/bend in the rod. Front hole and rod taper appear fine. Here's a pic of the recoil shield and bolt and extractor star and rod rear tip. (extractor star and rear of cylinder has since been cleaned).

 

[armorer951]

There can also be a slight amount of runout on the yoke barrel, and issues such as a "non-concentric" cylinder too. To determine these values, you'll have to cycle the action and measure the variances at the front and rear of the cylinder, between it (the cylinder) and the top strap.

In this scenario, the runout on the extractor rod can be zero when checked with the cylinder open, or with the assembly in a fixture. When in the revolver however, the tip of the rod will still not be concentric when it rotates. (splitting hairs here)

These are the things that PPC revolver builders loose sleep over.
(you know who you are)

Carter

 

[scruffy]

There can also be a slight amount of runout on the yoke barrel, and issues such as a "non-concentric" cylinder too. To determine these values, you'll have to cycle the action and measure the variances at the front and rear of the cylinder, between it (the cylinder) and the top strap.

In this scenario, the runout on the extractor rod can be zero when checked with the cylinder open, or the assembly in a fixture. When in the revolver however, the tip of the rod will still not be concentric when it rotates. (splitting hairs here)

These are the things that PPC revolver builders loose sleep over.
(you know who you are)

Carter

Carter, You were right the first time. I found it. For what ever reason, the front tip of the ejector rod is not pushing the front locking bolt in far enough on that specific chamber to just catch it by a hair making it more difficult to open. I watched it closely and compared it to how it works on other chambers. I can get it open, just more than normal force required to do so. Any suggestions?

The tip/face of the ejector rod looks squared (hard to tell by eye) and opening in the ejector rod appears fully concentric. I'm hoping opening the cylinder on that chamber enough times may wear it in to the point that it becomes easier to open. Not a huge deal as the cylinder opens easily in every other chamber position. It's my OCD making me crazy, but I like things to function the way they should. I should mention this is a range toy only and not carried or kept in the nightstand for any SD work so no worries about messing up a quick reload if I happen to run out of my six shots on that chamber.

 

[armorer951]

You can mark the end of the rod with a Sharpie and stone across the end to remove a bit of material there. Try to keep the cut at the tip at 90°.

Another very easy way to shorten the OAL of the extractor rod tip in the assembly is to remove the extractor rod collar, measure it's length, and then lay it on a stone and pull the bottom ribbed end of the collar back and forth one the flat of the stone until you have removed the desired amount of material, then re-assemble and try for the desired effect. .001" at a time is what I remove. This shortens the collar, and also shortens the assembled extractor rod by the same.

The only problem with this procedure is that the extractor rod has to come off, which means it may develop run out that needs to be dealt with when you put it back together as an assembly.

May be easier to just stone or file the end of the extractor rod a bit until the desired outcome is achieved.

Carter

 

[scruffy]

You can mark the end of the rod with a Sharpie and stone across the end to remove a bit of material there. Try to keep the cut at the tip at 90°.
May be easier to just stone or file the end of the extractor rod a bit until the desired outcome is achieved.
Carter

I'm confused. If the rod is not pushing the front locking bolt in far enough (when that one chamber is lined up) and the bolt is lightly catching on the collar, wouldn't shortening the rod make it worse? I would think slightly shortening the collar (the front hollow part of the extractor surrounding the rod tip?) would make sense so it doesn't catch, but not shortening the rod. What am I missing?

 

[armorer951]

The extractor rod is not pushing on anything, the center pin is doing the pushing. (on the front locking bolt)

Relieving the end of the extractor rod, or shortening the extractor rod collar, simply makes it possible for the center pin to come past the end of the extractor rod a bit (.010" or so).....like it's supposed to.

Shortening the OAL of the extractor rod collar has no affect on the OAL of the center pin when all the parts are assembled.

 

[scruffy]

The extractor rod is not pushing on anything, the center pin is doing the pushing. (on the front locking bolt)

Relieving the end of the extractor rod, or shortening the extractor rod collar, simply makes it possible for the center pin to come past the end of the extractor rod a bit (.010" or so).....like it's supposed to.

Shortening the OAL of the extractor rod collar has no affect on the OAL of the center pin when all the parts are assembled.

My apologies, Carter. I just looked up the proper name of the parts on the Numrich parts schematic and I was mistakenly calling the center pin the "rod" and it is the rod collar that I'm going to take .001" at a time off until it clears the front locking bolt easily. Looks like that is a fitted part (extractor rod) as I can see the collar has been lightly filed previously after it was blued.

Thanks again for your help. I learned a lot tonight. - Bob