Hi , I have a 48 no dash that I bought with a second serialized LR cylinder.
It had the LR cylinder in it when I bought it , which works perfectly.
I decided to put the Magnum cylinder in it and shoot it. I did not check gap at this point , but it spun freely. It lasted about two cylinders before it froze up.
I checked and found gap to be 2-3 thousands.
I then made the silly decision to buy a second gun here on this forum, I should have asked the fellow to check gap , but what are the odds ?
Well here I go again, 2-3 thousands and less then two cylinders before she locks up.
What gives ? I have a nice little Model 51 I can shoot all day long !
I have also owned other 48's that shot fine.
My local gunsmith says he will turn the cylinder down on his lathe.
Smith & Wesson says they will only file the forcing cone, which will mean I can not use 22LR cylinder as well.
Anyone have any thoughts ?

It doesn't take very much to go either way, I'd NOT turn down the cylinder, and we usually do as the factory said and take ever so small off the rear of the barrel, depends on just what the "gap" is on the .22 lr cylinder, that would a the determining factor...also need to check the upper crane leg, that can be adjusted too, not much needed in the way of fouling or lead splatter on the face of the cylinder to make the gap "close" when its that close...nature of the beast......I'd recut the forcing cone also to help reduce the leading,may be a bit tight.........
also the brand, type of ammo you are using can and will "affect" this happening................
close is GOOD,but not when there is the chance for excess fouling/leading, that's one of the reasons for keeping in the .004-.006" max range

__________________
dan
NRA Benefactor,PMA

Did your local gunsmith check to see if the headspace and endshake was correct with the 22Mag cylinder? Did he check to see if the ejector rod was not bent? One would think both cylinders were properly fitted at the factory, but it is also easy to imagine how a loose cylinder assembly might get damaged. Before you do non-reversable machining on your gun, consider this:

Install a brand new ejector rod on the problem cylinder. See if this stops the binding up.........assuming of course, that this "freezing up" is caused by interference at the barrel/cylinder face. Installing a Power Custom .002 cylinder endshake bearing will set the cylinder back, adding an extra .002 to your b/c gap. Just make sure you have not reduced headspace to the point where the extractor ratchets are contacting the recoil shield.

I too would be leary of a gunsmith that declared he would face off the cylinder to remedy your problem of cylinder binding during firing.

The factors that interact during cylinder fitting include: headspace, B-C gap, endshake, timing, ratchet fit, etc. If your gunsmith truly does not understand this, then you should find someone else to work on your gun.

Well, I got a call back from Smith from a Performance Center Gunsmith named Vito . He said to send both guns in for a look. He said it was next
to impossible to have both cylinders work right on their double action guns and could I live with a too big gap on the LR cylinder ?
I said that was fine as I have 17's,18's and Model 617's . No shortage of Smith K-frame 22LR's here !
So , I will see how they can do, with the one gun being a mint 4 screw I won't shoot it any more anyway.
Thanks for all the ideas

<He said to send both guns in for a look. He said it was next
to impossible to have both cylinders work right on their double action guns and could I live with a too big gap on the LR cylinder ?>

I sure would like to have "Vito" come on this forum and explain why this is so. I just finished looking over a 17-4 and a 48-4. Both cylinders measure exactly the same 1.620" in length. Even the firing pin holes appear to be in the same position. I wondered about this, as the 22Mag case rim is .02" wider. The only difference I see is the chamber boring and the extractor. I've always wondered about this 22lr/22Mag convertible set-up. I've known a couple of people that had the Ruger Single-Six dual cylinder guns. They didn't seem to be especially accurate shooting 22lr. I always thought this was due to the fact that the smaller 22lr lead was being fired through a bore that was larger to accomodate the 22Mag bullet. Sounds like Vito is simply waiting for your gun with file in hand. They may be getting backlogued in the old PC and don't have a lot of time to properly fit cylinders. Good luck!