My 657 cylinder is touching the back of the bbl. I have had a few and used shims to correct this. This one has no perceptible movement fore and aft. What is the acceptable fix. Shim it anyway, or file the back of the bbl, or ??

Charlie

Presuming the revolver is in fine or excellent condition other than this issue ... is there any describable fouling (smoke ring, etc) at the exit ports of the cylinder and / or the build up at or around forcing cone ? Mind, old lead foul rings might not be that easy to distinguish against the Stainless back drop.

The slightest build up here will give you the problem you manifest.

Clearances between cylinder and forcing cone should be "tight" but not tight enough you cannot sequence the action. For example, Dan Wesson's clearances are extremely tight and precise here.

If so, I suggest:

1. Remove the cylinder, then remove the extractor
2. use 500 wet / dry sandpaper with some WD 40 behind a small flat block of hard wood (e.g. 1/2" x 1/2" x 4" long) against the flat rear face (exit holes and surrounding area) careful to ONLY lightly sand the flat surface ... then carefully clean the fouling rings. If you think you're comfortable with it ... you can use a very fine India stone cut this same dimensions. If you've never used India stones don't venture this process.
3. Bronze / Brass brush and Hoppes #9 across the face of the forcing cone
The bronze or brass brush will leave a copper-gold halo on the stainless that will wipe, wash or lightly buff off when finished.
4. Reassemble, lubing working parts in the process.

Yes, some will say the Hoppes might do long term damage to the stainless, nickel, blue etc. Just make sure you thoroughly neutralize or flush well with WD 40 until you've purged all remnants of the Hoppes.

I personally think Hoppes should make a cologne for men "Hoppes #9 ... for Men"

__________________
ANTIQUESMITHS
LM1300 SWHF425

Your first step is to properly diagnose what the problem actually is.
Just starting to alter things hoping to correct it is how things get ruined.

Causes could be a mis-fitted barrel, a sprung cylinder yoke, yoke end shake, or some other problem.
Know what the problem is before altering something that might not be the problem at all.

If you're not absolutely certain what's wrong, have an expert look at it, rather then do damage that can ruin the gun or cost a lot more money to correct the damage before the actual problem can be repaired.

Hoppe's #9 "might" damage nickel but it can't harm stainless steel.

It could be that there is burnt and/or unburnt powder under the extractor that is taking up any endshake. The fix for that would be to open the cylinder and use an old toothbrush or similar to clean off the back side of the extractor and it's seat in the cylinder. Then see if there is any endshake. This may not be the problem, but it's a good place to start.