what is acceptable cylinder to forcing cone clearance on a 1905
4th 38 spec? If I did this correctly I measured .013.
wedged the cylinder forward and measured .004. difference
of .009, seems excessive. Is that too much? If so what are
the likely causes?

Yes, it's a lot. Older specifications allowed a barrel cylinder gap up to .012" if I remember correctly. With a .38 Special firing regular pressure loads, you are not going to notice much velocity loss with the wide gap. The problem with endshake is once it gets started it accelerates wear. Look at the front of you cylinder and see if you see bright rub spots and look at the breech end of the barrel and see if you see the same. If you do, those are not good. I would recommend correcting the endshake, as yours is excessive. What causes it is firing. It is to be expected especially ina revolver as old as yours.

__________________
S&WCA 1729

Thanks tennexplorer, I don't see any rub marks yet. Given the measurements from above would I start with endshake bushings? Is the objective to close the .013 gap or reduce the .009 difference? will the bushings do both?

The bushings will do both. They will remove the endshake, but unfortunately in doing so they will shift the cylinder rearward and increase your constant cylinder gap. I've installed endshake bushings on three of my Smiths now with great results. If it were my gun, I would install .006" worth of bushings and test it out. Your endshake will be reduced to a more acceptable level, and your cylinder gap will be large but still workable.

Installing bushings is easy if you follow the steps correctly. Please ask if you need any help with that.

I have heard that there is another way to fix endshake, where the yoke is (stretched?) slightly. It seems this would remove endshake without increasing cylinder gap, but you would have to ask someone more knowledgeable than I on that one.

You need to take the end shake down to about .001, and live with the cyl gap unless you ae willing to spend more $$$. Reducing the cyl gap involves setting the barrel back a thread and recutting the back of the barrel--not worth it on an obviously much used old gun, IMHO.

__________________
Science plus Art

Helpful thread. Search is your friend.

I just picked up a 28-2 that was showing drag from crud on the face of the cylinder after just 24 rounds.

Measured tonight. The forward measurement was hard without a 3rd hand but an .003 feeler was tight. I essentially had to force it in.

All the way back an .011 would barely go but a .012 wouldn't.

Almost the same difference as the OP. Guess I'll go with an .006 bushing too.

0.006" of shims is the best you can do right now. That will give 0.002" of endshake with a 0.011" B/C gap. You may find that after a few months, the endshake has grown to 0.003" as the shims settle in. At that point, you can add another 0.002" shim to get the the factory recommended endshake, if you wish. If you're not going to shoot the gun much, I wouldn't worry about 0.003" endshake.

Buck