17-4 Cylinder Swells with Heat?

[Talan2000]

Hi All,

I'm a smith newbie, but an enthusiastic one having been on an acquisition binge in the last 3 weeks -- 17-4, Premodel 14,15-3, and last 25-2.

Anyhow, I've had a few challenges with the 17-4 which seem to be rather common based on the threads I've read.

After shooting about 60-72 rds absolutely flawless in Single Action and Double Action I get significant resistance to the cylinder turning. Double action fails and the gun must be cocked to fire. Then it pretty much shuts down.

The cylinder appears clean, chambers too. Not running dirty ammo. Used eley club and CCI Minimag. Same result.

I initally thought, ok, I've got lead fouling under the star, on the forcing cone, etc causing the friction and or it doesn't like lead bullets.

I ran all variety of ammo through it from pricey eley club to blazer to copper plated HV federal. I encountered the usual tough to extract problem after the lube and or fouling got in the cylinder chambers -- and I can live with that -- BUT my issue is the friction preventing the gun from firing!

Took it to a gunsmith who addressed the forcing cone with a file very lightly. Back to the range and it worked better - no hiccups until about 100 rds THEN same old story...cylinder was warmish to the touch but not hot. Cylinder would hang - seemingly at the SAME one or two chambers -- the others didn't hang ( I marked them with sharpie).

I let the gun cool 5 or so minutes (no cleaning) and then the problem disappeared! Note also that the cylinder will turn just fine with spent shells in it after they are fired (weird unless I guess I checked this after it cooled).

Has anybody else encountered this? Am I crazy? How could it be possible for a presumably heat treated cylinder to swell enough to bind? Is it something else?

Any way to address this other than filing down the forcing cone another thousandth or two? Or should I just shoot 36 rounds, let it cool 5 min, then shoot some more?

It shouldn't bug me so much - but it IS so close to perfection as a DA rimfire with amazing accuracy I just want it to be perfect.

Thanks in advance for any useful suggestions

Todd

 

[steelslaver]

What is your cylinder gap when cool? Is it the same on all the chambers? How about end shake? When it is hot does it loose end shake? When it is hot can you see gap between cylinder and forcing cone? With the cylinder off the yoke, what does the end of the yoke tube look like? Is the end of the cylinders center tube smooth? With the yoke removed and the cylinder on how smoothly does it turn when pressed forward on the yoke tube? Experiment: Put yoke cylinder assembly in an oven and see if it tightens up when warm. 350F will not harm any spring or temper, but, no need to get it that hot.

I suspect the yoke tube to cylinder might be a bit tight, this includes to tight of end shake. Your cylinder face could be a little out of square.

Head treating will not change the coefficient of thermal expansion.

I have a model 18 that has fired a couple hundred rounds non stop without cleaning or cooling. The K22 I just got fired over 100 rounds without cooling. I don't think I can fire a 6 shoot 22 revolver fast enough to get it too hot, but then I have never really made an effort to do so.

 

[Big Cholla]

IMHO, steelslayer has it about nailed down for you. I would go back to that gunsmith and ask for 0.002" to 0.003" taken off the end of the yoke tube thereby creating that much more cylinder gap. If that gunsmith is any kind of machinist, he should be able to place the stripped cylinder on a granite plate and check the true runout of the cylinder face. There is a S&W armorer's tool fixture for checking all measurements of a cylinder, but darn few pistolsmiths even have it. ..............

 

[k22fan]

[...] I would go back to that gunsmith and ask for 0.002" to 0.003" taken off the end of the yoke tube thereby creating that much more cylinder gap. [...]

Shortening the yoke tube will give him excessive end shake and reduce his B/C gap. It will make his problem worse.

I own a 617 that has as close to zero end shake as they get and a .002" B/C gap. While being fired slowly it is behaving the same with recently produced CCI Blazer that did not get the bullet wax lube coating that older lots of Blazer got. Blazer is not the only .22 LR that is not what it used to be before the first Obama .22 LR shortage. I suspect his sticky cylinder rotation has nothing to do with heat and is entirely from fouling. I can not diagnose his problem without his revolver in hand but I can eliminate my tight K-22's sticky cylinder rotation by using old lots of .22 LR including old lots of Blazer. I suggest cleaning the 17-4 every 50 to 75 rounds.

Since to O.P. wrote he is new to S&W revolvers all add that inadequate B/C gap in older revolvers usually is from wear increasing the end shake. The ignorant owner's cure is to file metal off the rear of the barrel. The correct fix is to reduce the end shake back to what it used to be by stretching the yoke or installing end shake washers between the end of the yoke tube and cylinder. With the gun as clean as you can get it how much can the cylinder move fore and aft when closed? How much B/C gap is left with the cylinder pushed as far forward as it will go?

The front side plate screw is one other part that can allow the cylinder to move farther forward than it should be able to. Side plate screws are not intended to be interchangeable. The front screw is a fitted part. Can your 17-4's yoke move forward a little? That is one more thing that shrinks B/C gap.

 

[Peak53]

I agree that this issue is more likely related to fouling. When the cylinder locks up, have you tried removing the cartridges to determine if the problem remains? Is it possible that after the charge holes are fouled, the next rounds to be loaded aren't seating to full depth and binding on the back of the frame, preventing rotation? Filing off the back of the barrel sounds like a distinctly bad idea. All 4 of my K22s suffer from tight chambers and need to be brushed out frequently.

 

[Pisgah]

I have never owned a .22 lr revolver of any make that did not have this problem with some ammo and after some number of shots -- maybe 20, maybe 120. .22 lr ammo, with its waxy outside-lubed soft lead bullets, is by nature dirty stuff. With the worst-offending revolvers I have owned, I always made sure to carry a cleaning brush with me to the range so that every few shots I could use the dry brush to quickly clean the cylinder face and forcing cone, which would return the gun to service in seconds.

 

[Talan2000]

Wow, guys, thanks for the sheer volume of this feedback.

I feel a little sick if shaving the end of the barrel/forcing cone was unnecessary. I actually had to look away when the gunsmith did it ;( And I am sure glad that I trusted my instincts to ask for your advice before returning for more of the same...

I suspect that perhaps "something" isn't square as the hanging always occured on two chambers of the cylinder...but that may just mean those two chambers fouled because they are tighter...

It seems the consensus view is that fouling is indeed the cause - and that would explain why AFTER firing with expended cases in the cylinder, the cylinder would cycle freely and easily - either by spining or dry firing on the expended cases...

Perhaps these two chambers are a little tighter than the other 4 leading to more rapid fouling - most likely from waxy lube buildup than carbon which means the bullets don't seat fully down.

This would explain the visible scraping of 22 lr brass caseheads that happens when at its worst...

I don't think the revolver has an endshake problem -- it appears in very good shape and has the proverbial "fired very little" appearance one reads so often on gunbroker listings for every revolver made! I will get out my feeler guages and attempt to get a new more precise measurement. It was less than .006 before I did anything. I'll remeasure now and try to qualitatively assess how much the cylinder moves fore and aft.

I may hold off on baking it in the oven for now but will report back with my data.

But my question still remains - with all of this -- why would the problem go away after letting the gun cool without any cleaning?

Thanks so much!

Todd

 

[steelslaver]

If it is in like new condition I still suspect that the yoke to cylinder fit is to tight. That would also explain the marks on the case heads. To much end shake is a problem AS is to little. You should have about .002 forward to back movement in the cylinder, no less than .001. Pressed all the way forward I wouldn't want much less than .006 on a 22LF.

On the dirty chamber thought. Are you having problems ejecting and when you reload the chambers how hard is it to seat them fully? Some S&W 22 do have tight chambers.

 

[H Richard]

All firearms, revolvers, semi's, rifles etc. do heat up when firing. It sounds like your B/C (barrel/cylinder) gap is minimal. The older hand fitted K22's we all love had minimal (.002" - .003") clearance, and the combination of fouling on the front of the cylinder and the minimal B/C gap leave literally no margin for clearance once the cylinder heats up from faring. Used in a Bullseye match you would fire: slow fire 10 rounds in 10 minutes, then wait till all are clear to go downrange and score targets then back to fire next string. Timed fire, two strings of 5 rounds each in 20 seconds each string, then down range again to score, then the Rapid fire is 2 strings of 5 rounds each 10 seconds each, then down to score and wait until next match starts. There is plenty of time for the cylinder to cool down and normally never a problem, 30 rounds over about 30 minutes. I'm guessing you are firing maybe twice that fast or more, thereby the cylinder int having a chance to cool off. It is very possible the front of your cylinder may be .001" high in a spot or two, but it takes special tools to verify and fix that, maybe not all gunsmiths will have the tools or expertise to find/fix that. Old school was very common to file .001" or .002" off the rear of the barrel to increase the clearance. I would explore verifying the trueness of the cylinder front first before doing anything else. A B/C gap of .003" (with everything else correct) would enhance the accuracy of the revolver.

Regarding sticky ejection, having the chambers reamed with a SAAMI standard finishing chamber is the only real cure.

 

[SLT223]

That has happened to me with both model 17's and 18's. In both instances it was caused by filth accumulating under the extractor star. I honestly don't think you can produce enough heat in 60-72 rounds of .22 to cause enough thermal expansion to lock up the cylinder....unless maybe you have zero barrel to cylinder gap.

 

[Talan2000]

Data

Thanks for helping me with the context on slow fire. Indeed, my rate of fire was more like a machine gun compared to 30 min for a few cylinders. I fired DA every 6-10 seconds, reloaded, then repeated for 10-12 cylinders. so maybe 15 -20 minutes for 72 rds. Very pleased with the accuracy - 10's and X's at a wimpy 7 - 10 yards.

Ok guys I went out and took a number of measurements using my cheap automotive feeler guages and my japanese made dial caliper ( as opposed to me cheap digital one). I say all this because I'm a bit afraid that we're close to being within the range of instrument/operator error with these measurements.

First - pictures because everyone likes a picture: (sorry it's rotated, it's not on photobucket) 17-4 1980 vintage wearing altamont super rosewood stocks



The barrel AFTER smith work (how tight was it before??)



The cylinder, marked with a sharpie



It seems pretty obvious to me now that the bluing is gone on the front of the cylinder- signs of it rubbing for 35 years?

Sadly, I do not have a feeler guage less than 0.006. Hopefully this doesn't render the data useless...I improvised by cutting a sheet of printer paper and measuring it with dial caliper to be .0035 in. If data is <.0035 the paper wouldn't fit through. I have least confidence in the chamber width as I wasn't consistent in how deep I inserted the caliper and noticed belatedly that the chamber mouths were all wider at the top (.225etc) then in the apparently chamfered chamber...

The data: Cylinder (at Rest), Pushed Back, Pushed Forward, Chamber width:

#1 <.006, .006, <.0035, .224
#2 <.0035, <.006, <.0035, .223
#3 <.0035, .006, <.0035, .220
#4 <.0035, .006, <.0035, .221
#5 <.0035, .008, <.0035, .220
#6 <.0035, .008, <.0035, .221

Takeaway - the b/c gap sure is tight - less than a slip of paper at rest, and on averag .006 pushed back. pushed forward is almost nill.

so as I understand it "end shake" is likely something like .002?

As to the chamber width - how is one to measure this most accurately -- right at the chamber mouth or down a bit (mine are all down a bit). I know "a bit" is measuring with a micrometer and chopping with an axe

I did have some stiffness ejecting spent rounds last time, but nothing like I had before -- when I had to smack the ejector rod with a box of reloads to pop them out -- this was after a very detailed cleaning and ensuring chambers were dry.

And this cleaning proved useful, so I will try to heed the advice to take a cleaning chamber brush and a brass brush for the barrel (which never seems to show fouling nor the cylinder front). I may have to be stealthy as local ranges prohibit cleaning your gun on the line...

Anyway - appreciate all your help!

EDIT - One perhaps HUGE thing I forgot to mention is that this gun seems to have had its barrel replaced at the factory -- there is an R-S in a rounded box on the grip and a 5/80 and an interesting diamond shape on the barrel with maybe a 5. So my guess is that it immediately came back or never sold before being rebarreled. Maybe they didn't touch up the barrel? Dunno.



Todd

 

[SLT223]

It seems pretty obvious to me now that the bluing is gone on the front of the cylinder- signs of it rubbing for 35 years?

That's not bluing loss. That's lead.

 

[Big Cholla]

Shortening the yoke tube will give him excessive end shake and reduce his B/C gap. It will make his problem worse."


You are absolutely right. I don't know what I was thinking...On occasion I have insomnia and was composing when I was somewhat drowsy. .....

But, the OP has now stated that the cartridge heads are sometimes dragging against the recoil shield. That is an important clue. When a revolver is shot a considerable amount the cylinder takes on the most heat load and expands at a faster rate than the frame does. S&Ws do need a small amount of what we call 'end shake' to allow for this uneven expansion. Perhaps that is what I was thinking and just didn't finish my explanation in that this handgun needs the yoke relieved and then some more taken off of the end of the barrel. I would still have the end of the cylinder checked for runout. ...............

 

[k22fan]

SLT223 nailed the issue that has to be addressed before any further diagnosis is attempted. The front of the cylinder is heavily leaded which reduces B/C gap. I can tell it is lead by the color and radial smears left around each charge hole as the lead moved away from the B/C gap. B/C gap measurements will be wrong until the lead is removed.

To refute the heat expansion theory I should have written earlier that a dragging cylinder often will rotate freely after it is opened then reclosed. I presume a chip of lead or an unburnt powder flake falls or is scrapped off the back of the barrel or front of the cylinder during opening and closing.

The R - S within a rectangle was one of the stamps S&W used to denote "refinish standard" or in other words reblued. An S on the barrel flat was also used for "refinish standard" and the diamond for a major part replacement, presumably the barrel.

IIRC ideal end shake is 0.0005" to 0.002". B/C gap tolerances used to be 0.004" to 0.010" but I've read here S&W increased their maximum to 0.012". My hunch is your B/C gap will be within spec. after your cylinder is held back. If you decide to get that done I prefer the yoke barrel being stretched. That only takes a few minutes. Younger gunsmiths may have spent their time with case flinging machines rather than god's good revolvers so look for a smith with grey hair that's been in business a long time.

 

[SLT223]

To OP:

You are correct that the geometry of the cylinder is changing while firing. I think you are incorrect about what's causing it. The over all length of the cylinder is increasing due to filth accumulation on the face and underneath the extractor star pushing it out into the breach face. When I first bought my 17-5 (used) it locked up in about 40 rounds because of this. It stopped just as yours did: Double action became impossible, then finally single action became impossible.

The cylinder needs to come out of your gun and cleaned thoroughly. Clean the face of it, and under the extractor with a nylon brush and solvent. I'll bet good money your problems will vanish.

Rimfire ammo is extremely dirty. I've found it will cause fouling related function problems about 10x faster than centerfire.

 

[Talan2000]

Ok, so I feel more than a little bit stupid now.

That absolutely was lead. At this point, I'm confused, but pretty sure that I just forgot to clean off the front of the cylinder properly after the last outing, but that I DID clean it off in between the two test outings at the range...

Here's how the cylinder looks now:


I remeasured the BC gap off each chamber (having lost the sharpie on lead markings of course) and got .006 with one a little less than .006 at "rest" and pushing back on the cylinder between .006 and .008. All of which is within fine tolerances I believe. Note that one spot at about 5 o'clock. I think that might actually be rubbing as it won't come off and is perpendicular/radial to the cylinder machining lines...

So have we definitively identified the culprit now?? Lead buildup on the front of the cylinder after 60-100 rounds coupled with waxy buildup in the chambers leading to a combined push/pull exceeding the .006 b/c gap? .003 lead on the front and .003 fouling from the cylinders perhaps exacerbated by a warm cylinder expanding by maybe .001?

So - is this NORMAL -- for the cylinder to get totally covered in lead like this after 60 rounds??? I never saw that on my Ruger single ten. I'm confused...Why would this happen with nice tight tolerances?

I guess I will just need to go back to the range and pretend I'm in one of those slow fire competitions rather than a rapid fire one...of course to my mind that was the purpose of a DA rimfire revolver vs the Single Ten, but I digress.

I will confess that I don't really follow this yoke stretching business but I appreciate being enlightened to its possibility...

As for the gunsmith, he's pretty old old school in his mid 70's I'd guess and is supposed to be pretty well regarded in N. Texas. It's kinda hard to FIND a gunsmith around here so I was glad to have access to him.

I'm sure you guys can't wait for me to get in my Model 25-2 and start peppering you with questions about 45 Auto Rim, moon clips, and pin guages for cylinder throats .4525 or not

Thanks again for helping me out. I'd be (more) lost without your guidance!

Todd

 

[SLT223]

So have we definitively identified the culprit now?? Lead buildup on the front of the cylinder after 60-100 rounds coupled with waxy buildup in the chambers leading to a combined push/pull exceeding the .006 b/c gap? .003 lead on the front and .003 fouling from the cylinders perhaps exacerbated by a warm cylinder expanding by maybe .001?


Todd

Nope. You still need to get at the underside of the extractor with solvent and nylon brush. Same for the back of the cylinder where the extractor sits. Crud backing up under that extractor will lock up a cylinder faster than lead accumulating on the face.

 

[k22fan]

The rub mark on the front of the cylinder that is at 5 O'clock in your picture does look like it is from dragging on the back of the barrel but it likely occurred before your gunsmith filed the rear of the barrel. Its presence indicates the cylinder can move forward too far and ideally you'd correct end shake. Brownells sells a yoke stretching tool for about $25. The tool is a tubing cutter with a roller instead of a blade. They are not difficult to use but I like trying my first attempts at new things on inexpensive guns. If a gunsmith does not have one I'd take my revolvers to a different smith.

Some of the members here think installing end shake washers is the better fix. I don't like them because sooner or later a new owner dissembles the cylinder then not knowing where the odd thin washers on his bench came from throws them out. If as recommended the end of the yoke was squared off with a cutter before installing the washers then with the washers lost the end shake is worse than before the repair. S&W stretches yokes.

Take your time deciding what to do. Start with more frequent cleaning and different lots of .22 LR. With some lots of ammo my tight 617 is good for up to 200 rounds and with other lots the cylinder starts dragging adversely affecting DA in less than 60 rounds. I'm hopping that competition will return to the .22 rimfire ammo business resulting in better quality control.

 

[Hapworth]

Good thread -- lots of possible culprits identified. Although OP may have tracked down the issue, I'll add one more suggestion: stacking tolerances and head space.

As noted, endshake should be dialed in at approximately .001"; OP's sounds to be too tight, and if that's also throwing headspace into too tight territory, those factors combined with thermal expansion might account for the stiff double action as the rounds stack up.

I've had it happen...

Good luck OP, and keep us posted -- threads like this are a benefit to all.

 

[Culina]

My 17-3 will slow down after the face of the cylinder gets fouled. I have found that the copper washed and wax covered ammo seems to reduce the amount of fouling that accumulates. I normally don't put more than 150 rounds through it during a range trip and haven't had any problem since I switched over to the Federal bulk stuff that Walmart used to have.