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Old 10-10-2018, 03:09 PM
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Default Cylinder Gap on Old No Dash 686

After sending off my new-to-me 686 No Dash to S&W for some service work (cylinder release sticky and for "M"), I finally got a chance to fire it and site it properly. I also took the time to take some measurements of the cylinder gap on this gun, as well as my original bought new 686 No Dash. My measurements on at the bottom of page.

I followed the advice that I found on the following website:
castboolits.gunloads.com/Excessive-barrel-cylinder-gap

Check the barrel-cylinder gap WITH EMPTY BRASS IN THE GUN!

PASS dimension is the largest feeler gage size you can insert between the barrel and cylinder, protruding from both sides of the frame window, which permits pulling the trigger six times to rotate the cylinder through a full revolution without binding up.

HOLD dimension is the size which in the same test condition as above causes the cylinder to bind before completing a full revolution, with fired brass in the gun (substitutes for "rear gage").

END SHAKE or END PLAY is the difference between two HOLD measurements, taken both with, and without "rear gage" in place.

New builds before proofing min pass 0.003/hold 0.004

After proofing max pass 0.006/hold 0.008

Customer service max pass 0.007/hold 0.009

Cylinder gap over 0.012" should not be fired as you may stick bullet in barrel.

End Shake over 0.003" stretch crane arbor then recheck gap.

If HOLD gap after over 0.009 refit with "long" cylinder.

Current specs may vary, but this is how I built them in the 1980s.


My Gap measurements

My new-to-me 686 recent GB purchase:
  • Pass = .009"
  • Hold = .010"
  • Endshake less than .001"
Is the above too much gap at this point?
Or should I not worry about it at this stage and shoot the Kayrapp out of it?...



My original 686:
  • Pass = .005"
  • Hold = .006"
  • Endshake less than .001"
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Old 10-10-2018, 03:49 PM
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The original at .006 is pretty much what you want. The .010 is a bit wide, but will still work fine. Probably not worth doing anything about.
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Old 10-10-2018, 04:27 PM
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I have a few 686s and they all average out around .008". One no dash I have is .005". I would say anything above .010" is concerning even though I believe .012" is allowable.
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Old 10-10-2018, 05:23 PM
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Originally Posted by Toolguy View Post
The original at .006 is pretty much what you want. The .010 is a bit wide, but will still work fine. Probably not worth doing anything about.
Thanks for responding. What I am wondering about is... Is ther any way to determine how much energy/fps is lost for each additional .001" of additional gap? I have been searching for this specific parameter, however, I have not found such information thus far...

My best chronographs/radar readings indicate at least a 250fps differentiation between the two 686s, but the data is so limited (had really hard time getting LabRadar to record data from the recent purchase 686..). Have not been able to record SA rounds through my replacement chronograph. Will attempt ASAP, since my previous DA measurements resulted in a DOA chrono....
Suffice it to say that I HATE trying to shoot DA at ~13yd, through a regular "chronograph" with a DA-only revolver... ERRgh!...

Bottom line, I realize that I am going to lose "some" fps with a wider gap, but just how much is the question...
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Old 10-10-2018, 05:36 PM
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This is going to sound flippant and rude, and I swear, that isn't my intention. But... honestly, does it matter?

I believe it would definitely be interesting to know how much difference in velocity you might see but beyond interesting, I am left with "does it matter and if so, how?"
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Old 10-10-2018, 05:49 PM
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"ballistics by the inch" has some comparisons of velocity v. gap
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Old 10-10-2018, 06:17 PM
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Quote:
Originally Posted by Sevens View Post
This is going to sound flippant and rude, and I swear, that isn't my intention. But... honestly, does it matter?

I believe it would definitely be interesting to know how much difference in velocity you might see but beyond interesting, I am left with "does it matter and if so, how?"
OK, then please show me how it does NOT "matter".
All available research as I can find is that at .012" or more gap, you could/can end up with a squib. Good question, and THAT is why I asked it.
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Old 10-10-2018, 06:22 PM
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Oh, I see that despite my best intentions, you were offended.
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Old 10-10-2018, 06:51 PM
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Oh, I see that despite my best intentions, you were offended.
HUH?

Yes it matters. Why would you think it does not? I apologize, I was looking for data and not opinions. That does make a difference, so if you got confused about offering opinions where data was expected, then I am sorry that you did not understand the difference.
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Old 10-10-2018, 10:08 PM
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FWIW: (I hope this isn't too far off topic) Dan Wesson revolvers were supplied with a 0.006" feeler gauge to set the BC gap.
That's where I keep mine. I have tried 0.003" but it fouls too quickly and the cylinder starts to drag.
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Old 10-11-2018, 01:38 AM
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I read an article that compared velocity -vs- barrel-cylinder gap several years ago but can't find it right now. As I recall there was less difference than you'd think between a tight gap & a wide gap.

And that test was on the same gun (Dan Wesson, IIRC). You're comparing two different revolvers. It's widely acknowledged that two revolvers that are the same model, cartridge, ammo, & barrel length will not produce the same velocities. (Reference Speer #9: Why Ballisticians Get Gray!)

There maybe 100-200fps difference between two "identical" revolvers. Barrel-cylinder gap is not the only factor that affects muzzle velocity. Even if you knew definitively what difference the B-C gap "could" make, comparing your two guns wouldn't take into account all other factors that could be affecting the MV differences.

I don't think I'd lose any sleep over it until it exhibits other problems like excessive lead/debris spitting.

.

PS: Here's the link to the web page skipnsb mentioned:

BBTI - Ballistics by the Inch :: Cylinder Gap

.
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Old 10-11-2018, 02:13 AM
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You know you're getting old when someone refers to a 686 as an "old" revolver.
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Old 10-11-2018, 07:45 AM
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The poster from castboolit's approach to measuring barrel-to-cylinder gap is interesting -- somewhat different from what S&W and Kuhnhausen, and has a few odd details.

Empty brass in the revolver for checking carry-up? Yes. For gap? New to me.

Running the action with the feeler in place doesn't allow a free hand to hold the cylinder rearward while measuring -- an integral part of the process.

The before and after proofing, and customer service numbers seem about right; .006" is generally considered the ideal balance between performance and reliability.

Never heard the notion that a .012" gap will stick a bullet in the barrel, and has never personally been experienced shooting that gap and larger.

S&W and Kuhnhausen recommend correcting end shake once it approaches .006".

Never heard of a "long cylinder" approach to correcting gap, though it's interesting and I can see how it might work. S&W pulls the barrel, turns the shoulder back a revolution and refits.

Simply, to measure b-c gap, hold the cylinder rearward and the largest feeler gauge you can comfortably pass between the barrel and cylinder faces is the gap for that charge hole; repeat for each, as sometimes the cylinder face isn't perfectly true (and often the barrel face isn't).

And measuring endshake, the cylinder must be held rearward on the first measurement, but also held forward on the second.

The specs on both your 686s are fine, with the older one slightly preferred.

What really matters is how they shoot...
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Old 10-11-2018, 08:03 AM
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Quote:
Originally Posted by HorizontalMike View Post
...What I am wondering about is... Is ther any way to determine how much energy/fps is lost for each additional .001" of additional gap? I have been searching for this specific parameter, however, I have not found such information thus far...

...Bottom line, I realize that I am going to lose "some" fps with a wider gap, but just how much is the question...
The linked test from Ballistics by the Inch is a good read, and there are a few similar tests others have conducted over the years, but I agree they're few and far between.

The general takeaway is the greatest drop occurs between .000 and .001", numbers we're never operating at anyway, and the remaining drops are lesser and fairly consistent each step of the way out to about .010".

In all it averages to about 10 feet per second for every one thousandth gap increases, though as stated not in equal increments -- the biggest drop is front loaded. I recall that it starts to open up again once you get past .10" or .012", but would have to find the original test producing those results.

For revolvers with varying but in spec gaps, the difference will be negligible compared to other factors affecting muzzle velocity, with BLUEDOT37 spoke well on.
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Old 10-11-2018, 08:15 AM
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My thoughts on the subject are that if your b/c gap is tad bigger than you would like then just stick to shooting larger or higher weight bullets. I pretty much stick to 158 grain and 146 grain in WC. I never shoot 125 grain bullets in any of my guns as I feel they are not long enough to spread the b/c gap and especially on model 19's create too much forcing cone wear. The heavier weights will keep the forcing cone wear to a minimum. Of course if self defense is the plan then carrying it with 125 grain is not a problem as shooting off only a few in the guns lifetime is going to make no difference at all. I spoke with Hodgdon about using magnum powders and their thoughts agree with this on shooting heavy mag loads. good luck
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Old 10-11-2018, 08:17 AM
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Quote:
Originally Posted by Sevens View Post
This is going to sound flippant and rude, and I swear, that isn't my intention. But... honestly, does it matter?

I believe it would definitely be interesting to know how much difference in velocity you might see but beyond interesting, I am left with "does it matter and if so, how?"
Maybe just ask the question plainly and convey that you're sincerely interested?

One answer is this:

It matters because if you require specific terminal performance from a specific load, and that load has specific (sometimes narrow) parameters (like muzzle velocity) in which it can be expected to perform as designed, you need to know the firearm you're using is capable of delivering the bullet within the critical thresholds.
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Old 10-11-2018, 08:58 AM
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If there's a difference of 250fps (That's huge!!!!) between the 2 revolvers, it isn't the cylinder gap.

Cylinder gap ='s +/- 10fps per 1/1000th of gap.

Not only have I read the above statement, I have test it and found it to be true numerous time while working up loads for accuracy in my dw's.


It's common to move the cylinder gap in and out along with raising & lowering the tension on the bbl nut to tighten groups up with the dw's. Changing the cylinder gap has always changed the velocity over the decades and 3 different chronographs. It's always been +/- 10fps per 1/1000th's cylinder gap.

Myself I don't use/shoot anything over 7/1000th's cylinder gap. Start getting over that & things go south real fast. Never worried about squibs, was more concerned with things like flame cutting & forcing cone erosion.

Not a s&w or 586/686 expert by any means, but seeing how you've been so kind to me in the past I'll pass along what I've learned over the years and a little bit of ammo.
Bought my 1st 586 nib back in 1987, darn thing was like a laser.

Back in the 80's surplus powder was everywhere cheap, couple that with cheap primers and free lead. The end result is large amounts of range time. I kept tract of how many primers I bought to make reloads for that 586. At the 100,000 round mark I sent it back to s&w, the timing was wore out. S&W also set the bbl back and redid the forcing cone. At the 200,000 round mark that 586 needed the timing redone again. Got the work done and the forcing cone re-cut. At the 275,000 round mark I noticed the velocities were dropping when using the same loads (100fps drop) I've used/shot/tested in that 586 for decades. I used that 586 as a benchmark when testing firearms of the same calibers. Always take a known performer along with a unknown firearm to the range for the 1st couple range sessions. Anyway that 586's bbl was finely shot out, hence the drop in velocity. Keep in mind that firearm saw it's share of powder puff/target loads. But it also saw countless 1000's of fullhouse 357 loads. Here's what that 586's bbl looked liked when I pulled it.

As the cylinder gap gets larger the flame cutting & forcing cone erosion happens faster. This is why anything over 7/1000th's I don't use/shoot anymore.

It depends on what you want the 686 for. Right now I have 2 of the s&w l-frame series 357 revolvers. The 1st 1 is a 586 l-comp

It is designed for sd plain and simple. It's comped, has recessed cylinders that are cut generously (large at the back end/loads faster & cases fall out quicker) and a 6/1000th's cylinder gap with less than 1/1000th's endshake. Basically it's designed to load/unload fast, not bind & comped for hot loads. The bbl is listed @ 3" but is really 2 1/2" long with a 1/2" comp in the bbl shroud. Even with the 6/1000th cylinder gap & 2 1/2" bbl that 586 has no problem delivering 158gr hp's @ 1200fps on demand with loads that are under max with 2400 & home cast/coated bullets.
Now this 686 on the other hand has extremely tight cylinders. Spent cases from that 586 l-comp need a hammer to get then to seat all the way in the 686. It also has less than 4/1000th's cylinder gap and less than 1/1000th endshake.

Same bullet used in the l-comp 586. But now it's loaded for accuracy in the 686.


2 different l-frame 357's from S&W. 1 is designed/made for sd & the other for target work. One is loose & the other is tight. You need to decide what you want to do with that 686.

IMHO, 8/1000th's is just too much.
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Old 10-11-2018, 07:15 PM
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Question Hmm?

forrest r said: "...2 different l-frame 357's from S&W. 1 is designed/made for sd & the other for target work. One is loose & the other is tight. You need to decide what you want to do with that 686..."

Precisely.
What I want to do with this second 686, is to use it as my shooting platform for testing out loads from .38 Special to .357 Magnum. My original 686 is nice enough to NOT want to put it through that kind of abuse as a test-load platform/gun.

I wonder if it would be cheaper/shorter to have a local GS shave 0.005" off of the barrel shoulder, than to send it back to S&W. FWIW, this last trip to S&W took almost 2-1/2 months. Not so much worried about the cost, but more so about the down-time waiting... And final question is, if S&W would actually do the above shaving since they normally consider that 0.010" hold gap to be within "specs"...?

I understand what you are saying about:
"...Cylinder gap ='s +/- 10fps per 1/1000th of gap...." but still wonder out loud if that "constant" may expand exponentially at the greater b/c gaps, especially above 0.008" gap. Surely there must be some point of diminished returns as one approaches the "do NOT fire" gap of 0.012" one would think...
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Old 10-11-2018, 08:13 PM
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OK, you can't just shave 0.005" off the barrel shoulder. The front sight would end up at about 9:30 o'clock when properly torqued. You'd have to come back one complete revolution (0.0277 in+/-) and then recut the forcing cone, b/c gap and shorten the extractor rod & center pin.

You bought it as a shooter, why don't you just shoot it as is? Your load to load variations will probably be greater than any variation caused by a larger than ideal b/c gap.

Last edited by WR Moore; 10-11-2018 at 08:14 PM.
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Old 10-12-2018, 06:25 AM
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OK, you can't just shave 0.005" off the barrel shoulder. The front sight would end up at about 9:30 o'clock when properly torqued. You'd have to come back one complete revolution (0.0277 in+/-) and then recut the forcing cone, b/c gap and shorten the extractor rod & center pin.

You bought it as a shooter, why don't you just shoot it as is? Your load to load variations will probably be greater than any variation caused by a larger than ideal b/c gap.
I wondered about that, but not having an unmounted barrel to measure the threads, I was/am at a loss. So, the process of shortening the B/C gap is more involved than I had assumed.

QUESTION: Would replacing the barrel with a new one, eliminate the shortening of the extractor rod and center pin? I am assuming that the current widened b/c gap is a result of frame stretch, right?

The most recent trip back to S&W(last month), additional shims/washers were installed to eliminate the then current endshake. Wouldn't setting/shortening the barrel eliminate the need for such "added" washers and self-correct the loose endshake?
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Old 10-12-2018, 07:49 AM
Hapworth Hapworth is offline
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...

QUESTION: Would replacing the barrel with a new one, eliminate the shortening of the extractor rod and center pin? I am assuming that the current widened b/c gap is a result of frame stretch, right?

The most recent trip back to S&W(last month), additional shims/washers were installed to eliminate the then current endshake. Wouldn't setting/shortening the barrel eliminate the need for such "added" washers and self-correct the loose endshake?
Frame stretch can (among other factors) contribute to increased b-c gap and endshake, but generally the issue is the yoke barrel compacting with use and the corrective is stretching it; if S&W is using shims for endshake now I'm surprised -- that never used to be the factory fix.

As to diminishing returns in muzzle velocity past a certain b-c gap, I alluded in an earlier post to a half-remembered test that indicated after a certain amount of gap you do begin to see an increase in MV drop closer to the largest one seen in the .000" to .001" drop versus the rest of the increments out to about .010", but it was past .012" that this started to happen, if I recall and wasn't extreme -- you're well shy of it and it really isn't a pressing matter in your situation anyway.

More on diminishing returns, broadly...

Mounting a new barrel may or may not get you out of shortening the extractor rod and center pin, but the barrel face would likely still have to be cut and trued for ideal b-c gap.

And even then, there's a lot more that goes into addressing all the factors affecting bullet performance. What if you barrel swap (which needs to be done by someone with the right know-how and tools, at cost) and it turns out b-c gap wasn't a significantly affecting issue in your revolver after all? Is it timing? Is it charge hole diameter? Shoulder cut? Slow rifling? What if the new barrel introduces problems the old barrel didn't?

The revolver is a system. The factors affecting ballistic performance are throughout. Chasing one at a time when there isn't a glaring problem is likely a waste and may be counterproductive.

And it's still not clear exactly why? If this 686 is to be a load tester, you don't need it to wring every last bit of performance out of a given round, you just need to establish its baseline by running different loads and collecting the data, then compare other guns against it.

But if for some reason you insist, don't chase single (and variable affecting) factors like b-c gap -- send the revolver to a top-shelf revolversmith, explain to them your intended use for it, and ask the revolver be blue-printed stem-to-stern. That's the only way to address ever significant element in the revolver that influences bullet behavior. Of course, then you'll have more into that 686 and it'll be nicer than the one you're trying to preserve, and you might have to go buy another shooter for testing...
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Old 10-12-2018, 08:35 AM
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The only time I ever cared about the bc gap & velocity was when I was using/testing snubnosed revolvers. +/- 50fps is huge with sd loads that don't have a lot speed to begin with due to the short bbl's.

The potential for pre-mature wear and lack of accuracy was always my main concern when the bc gap got over 7/1000th's.

Look at it this way, draw a strait line and then another line at a draw a 45* intersecting the 1st strait line you drew. The further away from where the 2 lines crossed, the larger the distance becomes. Anything under pressure goes to the least point of resistance. You hit the loud button, bang the bullets off to the races. The cylinder also moves/jumps to the furthest point it can. This mis-alignment is negated by the angle of the forcing cone. If you look at the picture of the bbl I took off that 586 you can clearly see that not only is the forcing cone egg shaped, it is also starting to wear on the left side. The side that the cylinder swings open.

The longer the distance of the bc gap, the more distortion the bullet will have to withstand. Coupled with wider strikes on the forcing cone.

Don't know if you ever bothered to measure the length of the cylinder itself. They have a +/- of 6/1000th's to them. A simple cylinder swap could tighten the bc gap up. The last revolver I swapped out the cylinders in was a charter arms undercover. Doing so gained 40fps from a 38spl p+ reload using 158gr cast hp's and power pistol. The bc gap is now a tight 3/1000th's
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Old 10-12-2018, 08:41 AM
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Well... the only loads that I am really interested in are .38+P and upper end .357 Magnum loads in a 4 inch barrel. The .357 Magnum loads are for a 158XTP only. The .38+P loads (currently) look like 125gr Golden Saber, 125g and 135gr Speer, and 125gr XTP. I have found that I cannot get sufficient MV out of my 2-inch small frames for 158XTPs (no expansion).

That said, I have no problem using either my 2-inch or my 2.625-inch revolvers for that. Those lighter bullets are/were designed for lower MVs. Once I get those loads worked out, then the 4" 686 will only be for .357 Magnum loads of N105 at the top end, or about 1350-1400fps (out of my better 686). At least now I understand, at least roughly, how much MV loss to expect with the larger b/c gap.
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Old 10-12-2018, 08:59 AM
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Originally Posted by Forrest r View Post
The only time I ever cared about the bc gap & velocity was when I was using/testing snubnosed revolvers. +/- 50fps is huge with sd loads that don't have a lot speed to begin with due to the short bbl's.
...[snip]...
Don't know if you ever bothered to measure the length of the cylinder itself. They have a +/- of 6/1000th's to them. A simple cylinder swap could tighten the bc gap up. The last revolver I swapped out the cylinders in was a charter arms undercover. Doing so gained 40fps from a 38spl p+ reload using 158gr cast hp's and power pistol. The bc gap is now a tight 3/1000th's
So, as I understand it, my actual b/c gaps are pass .005" and pass .009". So my MV loss is/should be about 40fps between the two barrels since the difference between barrels is .004"...

Closer than what I was originally fearing. Boy that Wilson Combat spring and pin kit really lightened up the SA to almost a hair trigger, and that was with the heaviest 14lb rebound spring. The DA is pretty much now how I like it now.
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Old 10-12-2018, 03:07 PM
WR Moore WR Moore is offline
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QUESTION: Would replacing the barrel with a new one, eliminate the shortening of the extractor rod and center pin? I am assuming that the current widened b/c gap is a result of frame stretch, right?
Don't jump on unlikely causes when simple wear & tear is the most likely cause*. Don't confuse the various measurements and assume that if one is corrected, the other has to be excessive.

When your revolver was first assembled, it had acceptable headspace (0.060-0.068 inc), endplay and barrel cylinder gap (.004-0.008/0.012 inch depending upon factory tolerance spec). Now through wear, your revolver developed excessive endplay which was reset by the factory to an acceptable point. Previously, the cure for that was stretching the yoke barrel. I'd be surprised if they went to shims.

At that time, the headspace and b/c gap would have been checked to make sure they were within current tolerances. It would appear yours is considered within tolerance. Alternatively, the b/c gap was a little sloppy originally, they saw no reason to fix what ain't broke and/or the tolerance may have changed.

Now, yes, installing a new barrel would eliminate shortening the extractor rod & center pin. However, depending upon what the factory now considers to be acceptable b/c gap, you might not see any improvement (unless you send it to the Performance Center and specify desired headspace & B/C gap). On top of that, you'd be shelling out the cost of a new barrel plus labor and possibly plus other parts. It'd probably be a wash between reworking the gun with the current barrel and fitting a new barrel.

Why don't you just shoot the cotton picking thing? OOPS! it appears that's what you've decided.


* One employer issued the 681 and all training, qualification and other shooting was done with full power Federal 125 gr JHP Magnums. The guns got loose, would eventually get factory rebuilds but, SFAIK, we never stretched a frame despite tens of thousands of rounds per gun. OTOH, overzealous cleaning caused the replacement of several cylinders due to excessive wear of the face.

Last edited by WR Moore; 10-12-2018 at 03:13 PM.
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Old 10-12-2018, 05:55 PM
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Don't jump on unlikely causes when simple wear & tear is the most likely cause*. ...[snip]...
...[snip]... It'd probably be a wash between reworking the gun with the current barrel and fitting a new barrel.

Why don't you just shoot the cotton picking thing? OOPS! it appears that's what you've decided.

...[snip]...
That goes without saying, again. This new-to-me-686 was purchased 2nd/3rd/4th/etc. hand. Trying to counter/control/understand the level of abuse/use this gun had in the past, will at least assist in going forward. That is the point of this thread.

BTW, shooting the Kayrapp out of it, without any measurement of parameters, IMO is an exercise in futility. In other words, if you don't know where your started then HOW do you know where you are going end up, and when to stop with "adjustments" per say?
BTW..., I actually do want to shoot the Kayrapp out of it, BUTT take adequate notes as I do so in the mean time. To NOT do that, is tantamount to waiting on the Monday Morning Paper to find out if the proverbially "you" was a wanted individual for a murderous act, if you know what I mean...

I shoot PAPER, not people. Make a point of that please... Accurate information is required at all times... Thanks...

Last edited by HorizontalMike; 10-12-2018 at 05:57 PM.
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Old 10-13-2018, 08:31 AM
Forrest r Forrest r is offline
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So, as I understand it, my actual b/c gaps are pass .005" and pass .009". So my MV loss is/should be about 40fps between the two barrels since the difference between barrels is .004"...

Closer than what I was originally fearing. Boy that Wilson Combat spring and pin kit really lightened up the SA to almost a hair trigger, and that was with the heaviest 14lb rebound spring. The DA is pretty much now how I like it now.
Correct, you'll be in that +/- 40fps range.

Don't forget that using 38spl's in a 357 cylinder will also cost you +/- 10fps.

A simple test:
Load up fullhouse/hot 357 loads with cast bullets. Take plain white printer paper to the range along with a box to tape the paper to. Sit at a table and run 4 cylinders full of the hot loads with the box/paper on the right side next to the revolver (6" away). Put on new paper (save/mark the old paper gun side) do the left side. Switch firearms and repeat.

After both firearms are tested, take a good look at both revolvers looking for lead build-up around the forcing cone. Look at the paper for lead splatter/excessive powder marks.

No excessive lead build-up or excessive splatter ='s a tight revolver. Leading & splatter ='s the revolver is getting loose.

It takes a lot of rounds/hot loads to shoot a 586/686 loose. Back in the day I'd buy #32 (4 #8 jugs/1 case) of the ww820 pulldown powder from pat's reloading at the medina gunshow's. I'd burn that powder up in that 586 +/- 14gr at a time and more often then not the loads were north of 14 gr. That's +/- 15,000 fullhose loads to a case of powder. I never kept count of how many case of that powder I bought. But that's all I loaded/used for several years.

I do find it interesting with the comments on shorting rods/etc. When you re-barrel a s&w the most important thing is the forcing cone. More specifically the width of the forcing cone. The length of the ejector rods don't come into play. At the end of the day you're dealing with 28/1000th's of an inch when re-barreling a 686. Facing off the bbl take up most of that 28/1000th's. The rest is set with the cylinders.

Why do I have pictures of a 568 bbl in my hand? Because I bought a 4" bbl for that 568 with the shot-out 6" bbl. Put it on and ended up with a 8/1000th's bc gap. Shopped around and found a cylinder that was 4/1000th's longer then the original and put it on that 586. That 586 shot lights out with the new parts (4/1000th's bc gap) but it looked bad with the extremely worn frame. I didn't care was glad to have it back up and running. Ended up selling it to help fund a 686 competitor. Always like a 6" bbl for plinking/target work.


Another bbl change, this time a ca bulldog. Hated the high front sight!!! Why they would put a fish hook of a front sight on a pocket pistol is beyond me. Anyway picked up both of these ca pistols for $300. Note the wear/turn lines on the ca undercover. The picture I posted a couple days ago is the same revolver with a cylinder swap.


Put a longer bbl (2 1/2" vs 2") new style (lower front sight) on that buldog with a 6/1000th's bc gap.


Now that bulldog is a lot easier to carry & is a real thumper.


You should test that 686 to make sure it hasn't been shot loose. If it's tight, shoot it till it is loose.
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Old 10-13-2018, 01:50 PM
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I had an eight year old 686 that I had to send in, due to bullet frag
coming back at me.

I have been too busy with the 38 J frames and 9mm's to shoot it
but I will get to test it out soon.

Hope that "Tight" revolver does well, for you.
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Old 10-13-2018, 08:27 PM
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My brain is itching from all the data and statistics.

I can predict with absolute certainty that there is greater velocity variation shot to shot in a 50 round box of ammo than there is in the "barrel/cylinder" gap variation.

Really ? ? ? Sometimes it is just fun to go to the range with guns & bullets just for the joy of shooting. Like this (quoted from Match Results):

The Pistol Challenge went good on Saturday [10-06-18] and we had fun. We had 17 shooters mostly members.

Max Possible is 300 with 30 - X

First Place:: Archer B. - 298 / 17 X --- S&W model 41 22 LR
Second Place: Frank D. - 287 / 10 X --- Colt 1911 National Match 45 ACP
Third Place: Col. Bollinger - 285 / 4 X --- firearm unknown

Engineer1911 as the only shooter who has shot in a sanctioned match, did a demonstration shoot with a 38 Spl M-15 S&W with a 2 inch barrel shooting all double action - 293 / 11 X.
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