Triple Lock Cylinder

[StrawHat]

On another forum I was telling about my New Century and my plans for building a replica revolver sent by S&W for the 1906 Army Trials.

I received this reply,
“ I found this thread a little late to comment. I'm pretty certain that the triple lock revolvers, the New Century's, had a different dimension of bore center to cylinder axis center than later N-framed revolvers. I cannot remember if that was true of the .455 chambered guns sent to the British. That dimension needs to be measured on your gun's original cylinder when someone re-chambers the 38 Special cylinder that you intend to use.

Maybe some Smith & Wesson collector/gunsmith can chime in here to confirm what I'm remembering about Triple Lock cylinder dimensions but it will be safest to have chamber centers to axis center measured before cutting your replacement cylinder.

I have a .455 Triple Lock and can measure mine as well as 1917's and Heavy Duties, but that would not be the same as measuring your individual gun.”

And further elaboration,

“ The source that first brought up the differing dimensions I wrote about above is in _Smith &Wesson, 1857 - 1945_, by Roy Jinks and Robert Neal. There it is stated that the distance from chamber centers to cylinder axis center was increased .010" on the S&W .455 Second Model. I dont think I've read about it anywhere else , including on the Smith-Wesson Forum where I did read the OP's query about this cylinder question. “

Can anyone very this information? Not the citation but the fact that the charge holes are a different distance from the ejector rod? It seems like the cylinder window would need to be a different height also.

Kevin

 

[steelslaver]

I didn't disassemble any cylinders, but my 455 TL that has been converted to 45 colt measures 1.537 from outside of chamber to outside of opposite chamber and a 45 colt cylinder in a resent N frame measures 1.548. The TL cylinder measures 1.7085 OD and the N frame 1.7095 a 625 cylinder measured 1.555 and 1.715 OD

I have measured a bunch of cylinders, and actually they are not all that uniform and "perfect". Measuring a across the cylinder from chamber wall to chamber wall is not a great method for accuracy. I have stuck pin gauges in chambers and measured across those which is much better and found some amount of variations exist just within one cylinder. In fact I have found variations in chamber dimensions vary some from chamber to chamber of the same cylinder

But even the 2 cylinders at the far end in this case are 1.537 (TL) and 1.555 (625) the radius of those would be .7685 and .7775 a difference of .009 from C of cylinder to outside of chamber. But notice there was also difference between the 2 modern cylinders .007 overall and .0035 in radius.

Here is a kicker the titanium 45 acp cylinder in my 325 carry gun is 1.565 LOL

I do have a TL 44 special cylinder in my shop I can check tomorrow and I will use pin gauges

 

[steelslaver]

If I stick a tight pin gauge in a chamber then measure from its outside to the far side of the ejector center pin, then subtract 1/2 the pin's dia and 1/2 the center pins dia, I should have a true C/L to center of chamber. 44, 45, 357 should not mater

PS as I also have a 2nd model 455 I can check that also

I will say that trying to rechamber a cylinder from 38 to 45 and offsetting the 6 chambers all the same amount and distance from CL would be somewhat challenging

You would need to set up on chamber center, then move the cylinder the correct amount in the needed direction, then slowly re-cut it using something like a 4 flute end mill then use a chambering reamer with a pilot modified to size of endmill. Then repeat 5 more times

 

[Protocall_Design]

You could also set up the cylinder on a rotary table or indexing fixture and use a boring head and bar to get on location, then finish up with the chamber reamer.

 

[StrawHat]

My head hurts thinking of the machining nightmare to do what I am hoping is NOT necessary.

I just cannot imagine I am the first person to need to replace a cylinder in a TL and no one else has heard of this dimensional issue.

Kevin

 

[steelslaver]

Well I was thinking. I highly doubt the center line of the TL 455 cylinders are different than the TL 44 special one as S&W made a bunch of TL 44 special frames into 455s. If the chamber CL was different the hole in the frame for the barrel wouldn't work from one to the other. I guess you could modify the yokes, but not likely on something as precision made as a TL yokes and if you did that then you would need a way ID them to keep those from being interchanged

 

[Protocall_Design]

You could measure from the yoke barrel with cylinder out, to a gage pin in the barrel, do the math, and find the centerline of that exact gun. Then match that dimension on the cylinder. Then you're no longer just guessing.

 

[steelslaver]

True, but I have never approached fitting cylinders from that angle. I do know there is a bit of variation from one cylinder to another even in the same model and even from chamber too chamber on a single cylinder. How much tolerance is ok. How much variation and tolerance is there in yokes? How much variation is there in frames for that matter?

Interesting thinking about the possible effects of tolerance stacking in these areas.

It is actually kind of fascinating that revolvers function as well as they do and are as accurate as they are.

Really cylinders should first bored from the front right after their center bore is reamed and before being reamed from the rear for a cartridge. The alignment there is more critical than the rear.

 

[steelslaver]

I just measured 4 N frame cylinders
A non recessed 44 mag cylinder
A 44 TL cylinder
A recent SS 45 ACP with odd arms
A 455 TL cylinder

I stuck the larges pin gauge that would fit that cylinders chambers then measured from far side center pin to outside of pin on each chamber. Then wrote down pin size and size of center pin.

Then I took the next smaller pin for that cylinder's chambers and stuck it opposite of tight pin and measures OD to OD, and did this at all 3 possible positions

Here is what I learned


44 mag cylinder from center pin to outside gauge pin measured
.8350, .8360, .8350, .8280, .8280, .8310 for a variation of .008
Across the center from chamber OD to chamber OD
1.510, 1.515, 1.520
The center pin OD was .1235 and the gauge was .459. those added together and divided by 2 is .2913- so from CL to center of chambers goes from .5367 to .5447

The 44 TL cylinder was .8285, .8305, .8335, .8320, .8330, .8320 and a max variation of .005

Chamber to chamber 1.5205, 1.5220, and 1.5215

Center pin dia .1435 and .458 pin =.6015 /2=..3007+

So cl to chamber center from .5278 to .5328

The 455 TL

.8495, .8490, .8445, .8415, .8415, .8445 variation of .008

ch od to ch od 1.540, 1.555, .1.570

center pin .1450 and gauge pin .485 so added then divided by 2 that is .315 so CL to chamber center is .5265 to .5345

the 45acp cylinder

.8370, .8340, .8390, .8310, .8310, .8350 for a variation of .008

C OD to C OD 1.567, 1.568. 1.566

Pin gauge .478 and center pin .1240 =.602 and /2= .301

So cl is . .530 to .538

There is no doubt some small variations in my measurements caused by my measuring a round to a round. and not being 100% square. Really I should have put cylinders in a vice and held caliber dead flat. There is also some wiggle in the pins. But, I have previously found that cylinders are not all that perfectly machined, but the tolerances in yoke barrel cylinder, center bore, cylinder stop and notches in combination with the forcing cone makes up for those variances. It also may help explain why some guns are more accurate than others. Why sometimes one chamber doesn't group with the rest.

But on the original question of the variations in chamber radius from TL to non TL

The smallest TL radius was .5265 the largest .5345 which comes in real close (.0035) to the brand new 45 acp cylinder with .530 and .538

Neither nor the new acp radius are as large as the modern 44 mag's

But why is the 44 mag showing a larger radius than the acp???

But in reality .01 is only the thickness of 3 sheets of copy paper

I could go measure some more 44 mag and 45 cylinders I guess

I think I will take a nap instead, secure in the knowledge that when I actually shoot them they work and the bullets make a group. If the bullet leaves the throat straight, when it engages the forcing cone there is enough slack in the system that everything is brought into alignment and the bullet travels though the barrel and sent on its way spinning to maintain stability.

 

[StrawHat]

I am content to believe the center lines (or whatever the appropriate term is) are close enough to be considered good.

I could not fathom the idea that the cylinders could not swap, with work, throughout the N frame line.

Thank you all!

Kevin

 

[steelslaver]

I checked another 44 mag cylinder and got
.831, .830,.829, .830, .831, .833, and .830 max variation of .004

.459 pin and .121 center pin for .580/2=.290

so cl to chamber radius is .539 to .543

I believe part of the deal with first 44 mag cylinder was just a cylinder and ratchet and I just stuck a center pin in it. Where the rest were assembled with ejector rod and springs.

You get some play out of the center pin, the pin gauge is pretty tight so not much there. But, you need to keep calibers level as you rotate slightly back and forth on pins while keeping them slightly tight to get the measurement. If your not dead on square you do not get a true measurement. I notices when I went all the way across using 2 pin gauges, chamber to chamber all of them were more uniform and the biggest variation was only .002