Need advice and help - Centennial Airweight cylinder gap problem

[Malysh]

Yesterday I noticed something on my 1954 Centennial Airweight I never saw before.
I took it out of the safe for an annual cleaning. While empty, I notice some scrapes on the front of the cylinder face.
While trying to eyeball the air gap between the forcing cone and the cylinder face, I had to use a flashlight to see any light. When illuminated, I could see an air gap at 12 O'clock, but the cylinder face at the 6 O'Clock position isn't showing any light coming through.
There appears to be very minimal cylinder endshake, if at all. Lock-up appears to be fine.
So it seems that the bottom of the forcing cone and the respective contact area of the cylinder are making continuous contact. The forcing cone itself shows no burrs, gouges, or scrapes.

Obviously, the gun has a problem with the cylinder face/forcing cone air gap. I've had the gun for about 13-14 years. I only shot about 10 rounds of standard pressure Nyclads from it when I bought it. It's my favorite S&W snubby even though it's used in about 85%-87% cosmetic condition.

I'd like to know if the old fashion spark plug gap feeler gauges can be used to measure the air gap between the forcing cone and the cylinder face? I read the FAQ from this section to remind me of the gap tolerances, but I don't have any tools to measure it. If the spark plug gap gauges work, I'll go buy a set. I should have a set around anyway.

My second concern is how to fix this problem. What needs to be done, and can I do it myself? I am OK with doing minor repairs of many items but if this is best fixed by a professional I'd rather go that route.

I checked all of my 6-7 other J frames and all of them have a gap visible by eye (even my older eyes that need reading glasses). Their gaps are uniformly the same whether at the 6 or 12 O'Clock positions when viewed in profile.

Luckily, this Cen. Airweight is not in my carry rotation. I was bummed out to discover the problem but also glad I spotted it before I decided to shoot it at the range again.

Any help is appreciated, thanks.

 

[Delos]

Load it and look again

Put some empty shells in it and look at it again. (Or loaded ones if you are careful).

You will immediately see and feel the difference.

 

[sandwtrader]

Any chance the frame is cracked at the bottom of the barrel? A common problem for these early Centennials. I have a real beautiful example, 99%, with a crack clear across the width of the frame. If your gun has a cracked frame, the barrel may have moved around enough to upset the cylinder face/ barrel gap. I certainly would not shoot the piece in its present condition.

 

[Delos]

Check "end shake"

Gun Smiths have a word "End Shake" that needs to be examined. It might be important?

http://www.*************************/forum/s-w-gunsmithing/4771-end-shake.html

 

[Delos]

End Shake?

Well, try this one to get started. Anyway being loaded or not is a big deal when checking revolvers, particularly old chiefs.

(In other words if the cylinder is loose it might be tilted, when not loaded, in my unprofessional opinion. If I were you I would load it with empty shells and pull back on the cylinder, then look again. There are shims you can buy if the shaft is loose)
(I am not a gunsmith but I do read their posts. You seem to be stuck with me until some gunsmith jumps in)

http://smith-wessonforum.com/s-w-smithing/210412-end-shake.html

 

[Delos]

More on possible End Shake

Some good chat on End Shake. We all need to know these inexpensive fixes at some point.

http://smith-wessonforum.com/s-w-revolvers-1961-1980/162987-n-frame-end-shake.html


(All I am saying is to check this because it is easy and cheap. Never take a stone or file to something you have not checked really well. The rims of the cartridges do take up a lot of play on some revolvers. If I had a loose one I would never shoot it loaded with just one cartridge)

I bought a really loose Chief back in about 1971. Very educational. My new one is amazingly tight.

 

[Malysh]

Delos, thanks. I mentioned I looked for endshake in the first post. I don't think the gun has endshake problems. But without tools I'm just whistling in the dark.

sandwtrader, no, no cracked frame. I think the instances of cracked Airweight J frames due to barrel overtorque is out of perspective. I don't think it's a common problem. It has occurred enough that it bears mentioning. We have to remember that everyone who has a cracked Airweight is going to start a thread or a post and mention it. Nobody is going to start a thread "My Airweight Frame Isn't Cracked" and we don't have any idea how many owners of good ones are out there. So we have no sense of perspective to calculate a percentage of the total number of Airweights made vs. the ones that sustained frame cracks. I bet it's a relatively small number.
But I thank you for mentioning it!

I have always taken a flashlight and a magnifying glass to look at any Airweight I buy. If it's an internet sale I make sure I send the seller good pics of what it looks like and where to look and I have the seller check it before I bid and buy. I won't bid on "as is" auctions and I rarely buy Airweights with anything but a CC. I also tell them if I get the gun and it has a crack in the frame, it's not acceptable.

Frame cracking wasn't a problem necessarily with early Centennials any more than the other Airweight models. It occurred with Chiefs Special Airweights, Bodyguard Airweights, Centennial Airweights and M&P 2" Airweights here and there throughout Airweight production, up to and including some specimens I've seen right on this forum from the 1990s.

All I know for sure is that the cylinder face is definitely making contact with the forcing cone at the 6 O'Clock position, but that the gun's timing seems to be fine - for now.

 

[Fishinfool]

Is it possible your forcing cone is not cut square?

Larry

 

[Malysh]

Is it possible your forcing cone is not cut square?

Larry

That is my impression. But since I'm more used to shooting these guns than making mechanical assessments, I thought I just better ask

 

[Delos]

Flash Gap

I read your post again and saw your mention of End Shake after my last post. I felt a little silly at first.
However when you ask about the feeler gauges that auto mechanics use to check spark plugs I realized we are probably at similar learning levels on revolvers.

You ask about spark plug feeler gauges. Actually those are round wires on circular frame. Like me, you often use the wrong word between the flat folding gauges used on valve adjustment. I assume that is what most gunsmiths use, but have not heard one way or the other. One article said 6 or 8 thousandths was okay and 12 excessive?

Anyway you did not mention pulling back on cylinder (with a finger on each side of front of cylinder) and then looking at the flash-gap with a flashlight or well lit background. If you have a gap when pulling back on cylinder I would not be concerned about shooting it. The cylinder moves back when fired.

If the cylinder is binding I would think you would feel trigger resistance when shooting. (But you did not shoot much and it was long ago?) Sometimes the burned powder patterns on end of each chamber are worth looking at. Take it out and shoot it.

I was going to use my old feeler gauge to check mine but I could only find one in millimeters with big jumps. My new air weight chief will pass .15mm but not 20. I recall the American feeler gauges having many more fine measurements?

 

[Delos]

Not Square at barrel or ejector rod bent?

Is it possible your forcing cone is not cut square?

Larry

I once read about a bent ejector rod causing drag on some chambers but not others?

 

[Delos]

Not to change the subject

This is worth reading. They measured velocity with different flash gap measurements, and different barrel length.

BBTI - Ballistics by the Inch :: Cylinder Gap

BBTI - Ballistics by the Inch :: Cylinder Gap Test


Must be someone who knows what gap is too small. I once had a .22 rimfire revolver that would bind up after shooting a box or two. I cleaned under the extractor looking for brass brush wires and such but never found anything. Next time out it was good for another box or two. I did not know about measuring flash gaps back then.

 

[Malysh]

Anyway you did not mention pulling back on cylinder (with a finger on each side of front of cylinder) and then looking at the flash-gap with a flashlight or well lit background. If you have a gap when pulling back on cylinder I would not be concerned about shooting it. The cylinder moves back when fired.

I know you are trying to help, and I appreciate that, but read the first post again, 3rd sentence:
"While trying to eyeball the air gap between the forcing cone and the cylinder face, I had to use a flashlight to see any light. When illuminated, I could see an air gap at 12 O'clock, but the cylinder face at the 6 O'Clock position isn't showing any light coming through."


The gun hasn't been shot for 13-14 years but it has been dry fired and cleaned twice a year. No resistance was ever found with the trigger pull nor did the cylinder ever not rotate or rotate out of time. I can tell the contact between the forcing cone and the cylinder face is very minimal. There's no resistance to the cylinder rotation but it is definitely making light contact with the forcing cone.
The cylinder charging holes, forcing cone, ejector assembly, barrel bore, etc, are clean enough to eat off of (so to speak). And lubed. I am fanatic about cleaning and maintaining my firearms

No, it will not be shot again until this problem is corrected.
If necessary I will send it to S&W and they can fix it

 

[Delos]

Yes However

I know you are trying to help, and I appreciate that, but read the first post again, 3rd sentence:
"While trying to eyeball the air gap between the forcing cone and the cylinder face, I had to use a flashlight to see any light. When illuminated, I could see an air gap at 12 O'clock, but the cylinder face at the 6 O'Clock position isn't showing any light coming through."


The gun hasn't been shot for 13-14 years but it has been dry fired and cleaned twice a year. No resistance was ever found with the trigger pull nor did the cylinder ever not rotate or rotate out of time. I can tell the contact between the forcing cone and the cylinder face is very minimal. There's no resistance to the cylinder rotation but it is definitely making light contact with the forcing cone.
The cylinder charging holes, forcing cone, ejector assembly, barrel bore, etc, are clean enough to eat off of (so to speak). And lubed. I am fanatic about cleaning and maintaining my firearms

No, it will not be shot again until this problem is corrected.
If necessary I will send it to S&W and they can fix it

If you were not "pulling back on the cylinder", with empty shells in the cylinder, you have not done anything yet. You have not convinced me you have a problem.

 

[andyo5]

Any chance that a build up of lead or other crud is causing what you have found?

 

[Malysh]

Any chance that a build up of lead or other crud is causing what you have found?

No, everything is clean as a whistle.

 

[ralph7]

If you were not "pulling back on the cylinder", with empty shells in the cylinder, you have not done anything yet. You have not convinced me you have a problem.

How would this even the gap from top to bottom?
The op is asking about the uneven gap and I would tend to side w/the other poster that suggested an unsquare barrel face.

Malysh, is it the same on every chamber?

 

[Delos]

Old ones often built looser or got shot loose

How would this even the gap from top to bottom?
The op is asking about the uneven gap and I would tend to side w/the other poster that suggested an unsquare barrel face.

Malysh, is it the same on every chamber?

I have a slightly old M60-7 that looks like it is touching at the top of flash gap, with slight gap below. When I pull back on the cylinder I get a nice rectangular space of about 8 thousandths.

Naturally the shell expands and grabs the chamber when fired. So the cylinder is driven back depending on front to back looseness of cylinder with cartridges in it. (rims take up space and stabilize the cylinder on old loosely built revolvers)

My new 638-3 has no movement front to rear and the flash gap looks the same with pressure to the rear as not. It's perfect gap is about 5 thousandths. (Computer operated machinery is nice)

So my older one is pretty much the definition of almost excessive end shake. Or my cylinder on older one is slightly short? (Obviously the ejection rod and the cylinder release push the cylinder forward under spring tension).

Anyway older chief's special shoots fine. The cylinder meets the frame at center when empty and pulled back. When fired the cartridge rims prevent any upward tilting movement.

I hear that some can get so loose the hand slips off to the side early when it is trying to rotate the cylinder, sometimes not locking normally. In other words a cylinder that does not always lock up when dry fired empty, but locks up normally every time when it has shells in the chambers, is the definition of excessive end shake that is soon to be a problem (or so I read).

My oldest Chief Special's cylinder feels much tighter when loaded.

 

[Malysh]

How would this even the gap from top to bottom?
The op is asking about the uneven gap and I would tend to side w/the other poster that suggested an unsquare barrel face.

Malysh, is it the same on every chamber?

Yup, the marks from the forcing cone touching the cylinder face are present near all 5 charging holes. And the marks are all located where 6 O'Clock would be parallel to the forcing cone, and that is the area where no light can be seen passing through what should be the air gap.

It doesn't have anything to do with end shake.

 

[ralph7]

Think if you're good and careful with a file, you can straighten the forcing cone/barrel face.
If I have done it, you can, too. Use a marker or layout dye to gauge your progress. Slow and steady with a fine cut file.