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Old October 1, 2013, 05:49 PM   #1
MSD Mike
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Smith Model 15 Lockup

Is it possible to have a revolver lock up to well. I recently picked up a S&W model 15-3 that when the hammer is cocked for single action use the cylinder locks up with absolutely no radial movement at all. My concern is that if the cylinder is locked up this tight it wont allow the forcing cone to work properly to correct any slight misalignment that might exist between the cylinder and the barrel. The revolver does not spit or lead but it is not particularly accurate either. I shoots ok with my proven 38 special loads but not as well as I was hoping. My other k-frames do better. Cyl gap is .005
All other revolvers I own have a small amount of radial play in the cylinder, not much but at least a small amount.

Thanks
Mike
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Old October 1, 2013, 08:28 PM   #2
oldgunsmith
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Have you checked alignment with a range rod?
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Old October 1, 2013, 08:54 PM   #3
MSD Mike
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Don't have a range rod. As many .38 and .357 revolvers as I have I should have one. There isn't any spitting/shaving and no leading so I think alignment is ok. I will pick up a range rod to check for sure.
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Old October 2, 2013, 12:46 AM   #4
Tom Servo
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Quote:
Cyl gap is .005
That's right where it should be. Kuhnhausen spec is .004-.006. It might be a tad tight if cast lead is your thing, but that just means keeping it clean.
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Old October 2, 2013, 05:47 AM   #5
dahermit
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Quote:
My concern is that if the cylinder is locked up this tight it wont allow the forcing cone to work properly to correct any slight misalignment that might exist between the cylinder and the barrel.
I am trying really hard to understand your implication. If there is some "slight misalignment", are you of the opinion that the bullet striking the forcing cone slightly off-center, will push it back to the center before the bullet is deformed and have a negative effect on accuracy? Whereas a tight-but perfect alignment between the would be less accurate and actually cause problems? Not sure what your contention is.
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Old October 2, 2013, 07:42 AM   #6
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re:

Quote:
If there is some "slight misalignment", are you of the opinion that the bullet striking the forcing cone slightly off-center, will push it back to the center before the bullet is deformed and have a negative effect on accuracy?
That's why the Smith revolvers tend to have a little rotational play...by intent...as opposed to the Colts, which have a 2nd "step" on the hands that forces the cylinder tightly against the stop bolt, making the chamber to bore alignment more critical.

Remember that the forcing cone is just that. A cone. A funnel that uses the bullet and the slight play to align the chamber and bore. If there's a misalignment without the play, the side of the bullet is damaged worse, and depending on the direction of misalignment, can cause damage to the hand and star, the bolt and its window in the frame...and even the forcing cone.

This also provides for the Smith's "pre-time" feature, in which the cylinder locks into battery before the hammer reaches full travel, while the Colt lockwork times the cylinder just as the hammer breaks, also making the Colt's timing more precise. Of the two, I prefer the Smith & Wesson system, even though the Colt has a slight accuracy edge.

Consider one of the weak links in the 1873 SAA and its clones. If the hammer doesn't come to a full, positive stop just as the cylinder locks, the hand keeps pushing...and if the hammer is being forcefully cocked...wears the hand and ratchet quickly. The standard cure for this is to have a revolver smith install a positive hammer stop in the revolvers that are destined for the cowboy action games.

Mike...your Model 15 is supposed to have a little rotational play. It's possible that somebody fitted a new hand to it, and neglected to make sure that it was there. It really should be corrected.
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Old October 2, 2013, 04:20 PM   #7
MSD Mike
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Thanks 1911, good info. That's kind of what I figured. Funny thing is the tight lockup is one of the reasons I bought the gun. Then I got it home and got to thinking. I suppose if the alignment is perfect its probably not a bad thing but I think it would be a stroke of luck for all six chambers to be perfect. I always like to learn and do most of my gun repairs myself so I'm not opposed to trying to correct it myself. I have Kuhnhousen's S&W book, sounds like I need to study up on the section that discusses fitting the hand.

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Old October 2, 2013, 07:26 PM   #8
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When the hammer falls, there should not be play in the cylinder. The alignment between the bore and the cylinder throats is called range. There is specific specifications on revolver ranging.

Diameter of ranging rod is 0.011" to 0.012" smaller than the bore diameter. .357 for instance, it will be 0.345" to 0.346".

With the revolver in fired configuration, i.e. hammer drops and trigger to the back, drop ranging rod from muzzle into cylinder. Repeat for all chambers.

The rod should go in all chambers by its own weight. It is acceptable to have up to 2 chambers with "tick". Any chamber with stoppage the revolver fails range specs.

It is possible to correct range failure. Gunsmithings are trained to do that, especially in the old days. It involves bending the frame.

That's what I learned from gunsmithing school. I saw the instructor demonstrating on a S&W, but I haven't had a chance to do one myself yet. Soon I will. I have a colt police positive that is slightly out of range.

-TL
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Old October 2, 2013, 09:15 PM   #9
MSD Mike
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Interesting info. I don't have a range rod but do have pin gauges and using a .345 gauge it passes this test with flying colors. I do have to say that this seems to leave a lot of room for error though. The largest gauge that fits in the barrel is .345 and my cylinder throats are .358. It seems as if the cylinder could be out of alignment by up to .0065 and still pass the test. Do I have that right or am I missing something.
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Old October 2, 2013, 11:44 PM   #10
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I went back to check my notes.

For .357, the range rod diameter is .345" for normal grade revolvers, and .346" for match grade. There is another unofficial method to determine the ranging rod diameter in case you bump into a odd ball caliber. It is the land diameter of the bore minus 0.002".

Using pin gauge is an acceptable poor-man method. But make sure whether your pin gauge is a minus or plus set. For a minus set, the actual diameter is the indicated value less 0.001", the other way for a plus set.

You mentioned your revolver passed the test with .345" pin gauge. It is excellent indeed if all chambers cleared without a tick, especially .345" is the land diameter. That's why you don't have spitting, and the gun shoots well.

As far as I know (I'm not quite a gunsmith yet, mind you), this is the way to check range of the revolver. I wouldn't say it can be off by 0.006", more like 0.004" to not to have a tick. 0.004" out of 0.357" (1%) is no easy task, as it is for all chambers.

Hope this helps.

-TL

Last edited by tangolima; October 2, 2013 at 11:56 PM.
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Old October 3, 2013, 04:18 AM   #11
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re:

Quote:
When the hammer falls, there should not be play in the cylinder.
I guess Smith & Wesson has been doin' it wrong all these years. Every one I've owned...new or used...has had a little rotational play when the hammer falls.
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Old October 3, 2013, 12:29 PM   #12
tangolima
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Let me go back and recheck my notes. I took the revolver course months ago. I might have missed a few details about S&W in particular.

Since I don't have a S&W to look at, could you please provide the follow information?

1. In the fired position, what is the direction of the rotational play? Clockwise and counter clockwise? From the shooter's point of view that is.

2. How much is the play in terms of thousandths of inch?

3. When you cock the hammer slowly, observe the movement of the bolt (cylinder stop) and the cylinder. How soon does the cylinder start to move after the bolt ball pops down? After the hammer is cocked, continue to cock the hammer back. Does the cylinder continue to move all the way through, or it would stop somewhere?

Thanks. It helps me learn.
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Old October 3, 2013, 05:29 PM   #13
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OK, I checked my course materials, and I'm most certain that the play is not supposed to be there in the fired position. It is a general principle applies to all revolvers, S&W included.

When the trigger is pulled (DA) or the hammer is cocked (SA), the hand should be in contact of the ratchet at all time, pushing the cylinder till it is stopped by the cylinder stop, right after the hammer drops. The cylinder ends up locked in place between the stopping cylinder stop (Colt calls it the bolt) and the pushing hand. It is proper cylinder indexing.

The play happens when there is wear in the hand. It is called out of time. It happens more in S&W than in Colt because of the design difference. Colt has a 2 stage hand, so the hand is still pushing the ratchet right on when the cylinder is indexing up. S&W has one stage hand. Near index the hand is almost side-by-side to the ratchet. Left side of the hand is constantly rubbing against the ratchet, and metal tends to wear faster. When it happens, the hand is no longer pushing the cylinder to index, and hence the play.

Out-of-time hand is a common repair item for S&W revolvers. The fix usually involves a over-size hand, bending the tip of hand to the left, and / or filing off the left side of the hand window. As usual, after the repair, the revolver must be checked to ensure left, neutral, right sings.

-TL
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Old October 4, 2013, 10:37 AM   #14
MSD Mike
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Good stuff, this Model 15 lock’s up between the cylinder stop and the hand just as your saying. It shows very little wear on the ratchet and in fact mechanically it’s so tight I almost have to believe it’s been freshened up. It’s hard to believe a 1970’s vintage revolver doesn’t exhibit more wear.
To 1911 Tuners point, every other S&W revolver I have owned (quite a few) have had a certain amount of rotational play when locked up. This includes new guns. Most have shot better that this current Model 15.
If they are indeed supposed to lock up with zero play S&W has not been paying attention to that rule during assembly and I have several (with rotational play) that are super shooters.
I guess I will just shoot this Model 15 a bunch until it develops some rotational play and see if it get more or less accurate.

Mike
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Old October 4, 2013, 09:35 PM   #15
James K
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The Colt and S&W work a bit differently. The S&W hand moves up and turns the cylinder, then moves upward until the side of the hand is bearing on the ratchet. That can, depending on how tightly the hand is fitted and the amount of wear on the hand and ratchet, allow a slight rotational movement. Colt, on the other hand (OK, OK!), has a hand with two "fingers". The top one pushes on the one ratchet tooth to start the cylinder around, then the lower one picks up the next ratchet tooth to effect the final cylinder movement. The lower hand bears on the ratchet to keep the cylinder pressed against the bolt at the moment of firing, but before that there has to be enough play for the trigger to move.

Neither is the perfect system, but both are more than adequate in the real world. The S&W can loosen up enough with wear that the forcing cone really does align the cylinder with the barrel. In the Colt, with wear, the powerful hand can force the cylinder past alignment with the barrel, even distorting the cylinder notches, the bolt or the bolt window in the frame to do so.

Jim
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Old October 5, 2013, 07:29 AM   #16
dahermit
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Quote:
The S&W hand moves up and turns the cylinder, then moves upward until the side of the hand is bearing on the ratchet. That can, depending on how tightly the hand is fitted and the amount of wear on the hand and ratchet, allow a slight rotational movement.
I thought that the bolt and its fitment to the bolt slots on the cylinder determined lock-up and any rotational movement. You did not mention the bolt? It seems to me that the hand's function is only to turn the cylinder as it bears on the underside of the ratchet stud, but as it pushes that stud up wards, the hand looses purchase on the stud and becomes disengaged, resting on the side of the stud. It seems to me, that the hand then, cannot either advance the cylinder anymore, or keep it from turning backwards...the bolt then, would seem to determine lock-up and any rotational play. Or, have I missed something?
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Old October 5, 2013, 08:02 AM   #17
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So long all six cylinders pass the range rod test, I'd be happy.
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Old October 5, 2013, 08:13 AM   #18
dahermit
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Quote:
So long all six cylinders pass the range rod test, I'd be happy.
As long as the gun shot without apparent problems when I bought it, I would be happy. I wait until there is a problem before I worry about figuring out how to fix it.
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Old October 5, 2013, 09:03 AM   #19
MSD Mike
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Yep, the gun works and functions perfectly. I guess I am just a little disappointed that it is not more accurate so I would say there is a bit of a problem to address. All my other K-Frames seem to rely on the cylinder stop to lock up and this gun feels like my others when the cylinder stop drops in the slot on the cylinder. As the hammer reaches the full cock position the hand then locks it up tight. I think I will just burn a bucket load of wad cutters through it and let nature take its course. Its interesting that there seems to be two schools of thought on the lockup though.

Mike
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Old October 5, 2013, 11:21 AM   #20
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Quote:
Its interesting that there seems to be two schools of thought on the lockup though.
Too early for "...two schools of thought...". I am still waiting for a response.
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Old October 5, 2013, 04:51 PM   #21
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Try this experiment. It is more to the point if it is on a Colt.

1. Dry fire the revolver. Keep the trigger back and wriggle the cylinder. There will be little or no play. The bolt ball (cylinder stop) works with the hand to index up the cylinder.

2. Let go of the trigger and wriggle the cylinder again. The play will be more, at there should be play. The bolt ball is still in the cylinder slot, but without the pushing hand to take up the slag, the cylinder is not indexed up properly.

I don't mean to step on any toes, but the Colt design is generally regarded superior to S&W's. It is more complicated. Once initially fitted, it will have less wear and will be more tolerant to wear, and hence will require less maintenance. But it is much more difficult to work on should repair be needed. Our instructor said it the best.

"The Smith is like a pretty 20 something young lady born to a rich family, never has to lift a weight all her life. With constant pampering she will perform beautifully, or she will let you. A Colt is like a Russian woman pulling a plow. Never gives you any problem and never complains. But when she is sick, she really needs help. "
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Old October 5, 2013, 06:26 PM   #22
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Quote:
I don't mean to step on any toes, but the Colt design is generally regarded superior to S&W's.
Just courious...what general made that pronouncement?
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Old October 5, 2013, 07:16 PM   #23
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Withdrawn.

Last edited by tangolima; October 5, 2013 at 09:20 PM.
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Old October 5, 2013, 07:28 PM   #24
James K
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I didn't dwell on the role of the bolt (Colt) or cylinder stop (S&W) because it is irrelevant to carryup. The main problem with timing is failure to carry up, that is the cylinder is not turned far enough for the cylinder stop to drop into the cylinder notch. Once that happens, there is no need for the hand to keep forcing the cylinder against the stop, causing peening and wear on all the parts involved.

Jim
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