Cylinder Gap


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KevinR
January 21, 2010, 06:16 PM
How much space is too much, between brl and cyl???

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rcmodel
January 21, 2010, 06:24 PM
Between .004" - .008" is about perfect/normal.

More then .010" is, IMO, too much.

rc

dfariswheel
January 21, 2010, 08:00 PM
Recently, S&W has been passing gaps as much as 0.012" as "in spec".

EddieNFL
January 21, 2010, 08:19 PM
I'm with RC. When DW was producing revolvers, the feeler gauge supplied was 0.006" I used to set mine at 0.002" for silhouette matches. Had to keep a brush on hand to clean the cylinder face.

hardluk1
January 21, 2010, 08:35 PM
Another DW owner that sets his 357 and 44 at .002. Even may Charter Arms is at .002 and run flawless.

KevinR
January 21, 2010, 09:38 PM
Very interesting, I was just wondering because my S&W mod 60 357 is .008 No wonder it is so darn loud.

DWFan
January 21, 2010, 10:18 PM
A large barrel gap can sometimes indicate that the cylinder isn't square or true in the frame. Best to measure from both sides and at several chambers. Some Dan Wessons can have the barrel tightened down against the cylinder, the gun raised up to a light and the barrel unscrewed until the barest sliver of light appears....and still work smoothly. Actually, I haven't seen one that couldn't as long as the cylinder face is kept clean.

unspellable
January 21, 2010, 10:27 PM
Nominal for most of the Dan Wessons was 0.006. For the long frame SuperMags it was 0.003. Since the gap is adjustable, I've run a series of tests over the chrono with a 22 DW and a 44 Mag DW. When the gap gets to 0.012 the revolver will begin to spit crap back in your face.

A couple of considerations. The cylinder face is not a perfect plane at a perfect normal angle to the axis. The cylinder gap should be measured at the chamber where it is tightest if there is a detectable difference from chamber to chamber.

For serious work where reliability is the primary concern the gap should be in the 0.005 to 0.008 range with 0.006 being optimum.

For plinking, small game or deer hunting where reliability is not life or death it can be a bit tighter. Taking it down to 0.003 presumes a premium grade revolver that has a dead true cylinder face and minimal end play.

I think S&W allowing it to go to 0.010 stinks. And going to 0.012 is beyond the pale when you get crap blown back in your face.

Surprisingly, the cylinder gap does not have as much effect on velocity as you might suppose.

Jim K
January 22, 2010, 09:32 PM
You don't want it too small, either. The problem is not dirt or fouling but of binding caused by expansion of the cylinder from heat. I have seen a revolver with a very small B/C gap quit after firing as little as two cylinders.

Jim

Bob79
January 22, 2010, 09:44 PM
According to Ruger, .010 is within Spec. All of my revolvers seem to be between .006 and .009

The Lone Haranguer
January 23, 2010, 04:33 AM
Recently, S&W has been passing gaps as much as 0.012" as "in spec".
I had a M66 whose gap was near or at (possibly exceeding) this. (I didn't formally measure it, just "eyeballed" it.) The cylinder blast was bigger than the muzzle blast. I had them correct it.

340PD
January 23, 2010, 08:04 PM
I just checked four of my freshly cleaned Smiths. All were at exactly .004. Two were from the performance center and the other two were off the shelf snubbies.

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