Title pretty much says it all. As always, I appreciate the knowledge

.004-.012 depending on when manufactured. Applies to all models.

My 686+ is at the upper limit, and it's one of the two most accurate handguns I own. I would like to see a pic of the flash in the dark, though!

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Thanks guys. I had heard .004-.006". I actually have two; a No Dash and Dash 4. Both are .008". I have no problems with either, but I know there are bushings you can install between the yoke and cylinder to correct excessive B to C gap. Since I have no obvious issues, and max tolerance is .012", I'm not going to worry about it. Thanks again gents.

.004"-.006" is considered the ideal balance between narrow enough to maintain good velocity, and wide enough not to quickly bind from fouling build-up.

In Kuhnhausen, .008" is listed as the last stop off before some bullet performance starts to be lost, and in the old days .010" was considered the last measurement still in spec; Alk8944 is correct, S&W now extends that to .012".

The bushings you refer to do not correct excessive forcing cone-barrel gap, they correct excessive endplay, also known as endshake -- too much fore and aft movement in the cylinder.

The only way to correct excessive forcing cone-barrel gap is to pull the barrel and shave back the shoulder. As a good general rule, if your revolver is maintaining accuracy and doesn't spit or shave lead, you don't need to correct gap.

S&W's generall run large. In previous comparisons with Rugers, S&W revolvers will often deliver velocities several barrel lengths slower than other makes. This seems "bad" until we factor in that some revolvers might be used for defensive shooting at which point a larger BC gap becomes an asset.
I once lock up a Ruger Security-Six 6" barrel on the SECOND cylinderful of full power .357 Magnum loads due to the super-close BC gap and the forcing cone area expanding to bear against the cylinder face.

I have yet to see a new standard production S&W that was made after 1980 have a gap of less than .007 . And I've checked a lot of them .

Mine is .004, which is just as tight as I'd want it. Like everybody says above....that spec. has "slipped" on new production guns over the years. I had a 22 with a BTCG of close to .012. It would light-up-the-sky and sound like a 38-special, but it still shot very well and was as accurate as I was.

Happened across an early '90's Model 65 not long back with a gap of .006" on all six chambers. Every millimeter of that revolver was in perfect spec, and the action was the best I've ever encountered from the factory, unretouched.

It was a Lady Smith variant, and I wonder if those got special attention from the mother ship.

Nonetheless, in the overall your experience matches mine -- I usually see .008" to .010", with some variation sometimes chamber to chamber.

Maybe just luck...or fate, but I do not own a Smith with a BTCG in excess of .005. Of course....these are all older pre-lock mid-to-late 80's guns. 'Bout time I got lucky.

The 4 inch CS-1 I just picked up has a .0045 B/C gap, it was being sold as lightly to hardly every used and I would believe that. Not anymore though, I love shooting it with everything from super light .38 round ball loads to the most beastly magnums, fantastic accuracy so long as the shooter does their part.