Barrel/Cylinder Gap Question

[AJR337]

One of my revolvers has a gap of about .009/.010 ( measuring with the cylinder held back) but when I measure it after pulling/holding the trigger back (with snap caps), the gap is around .007.

I was thinking about having the gap tightened up a bit but now I'm thinking that I should just leave it?

 

[Alk8944]

Just leave it alone, it is well within current factory specifications. Even if you were to have the barrel set-back to .006 or less it is unlikely you would achieve any improvement in either accuracy or velocity. I have set back barrels from ca. .010" to as little as .002" to see how much improvement in velocity I would realize and the difference before/after over the chronograph was exactly 000FPS.

 

[robertrwalsh]

As long as it is shooting OK and not blasting back at you I would tend to leave it alone. I confess to liking the old specification (.004-.006) much better than the current specs which are much more generous, but that's just me.

 

[AJR337]

Thanks for the responses.

Nothing blasting back. Also, the timing, lock up, and alignment are all perfect.

I just reread the a post on how to properly measure the gap / end shake (quoted below) and according to those instructions, my gap is actually .007/.008 with around .002 of end shake so well within spec.

"When initially checking your revolver you should start by pushing (& hold) the cylinder forward & then measure the gap between the cylinder face & barrel breach.

Next you push (& hold) the cylinder to the rear & re-measure that gap.

(Admittedly it doesn't matter which you check first. The rearward reading will always be the larger (maximum) reading.)

The forward reading is B-C gap & the rearward reading is B-C gap plus (any) endshake.

Any difference between the two readings is the end shake.

You have to do both checks to come to a meaningful understanding. If you do one without the other you do not have the whole picture or all the details."

 

[AJR337]

Just leave it alone, it is well within current factory specifications. Even if you were to have the barrel set-back to .006 or less it is unlikely you would achieve any improvement in either accuracy or velocity. I have set back barrels from ca. .010" to as little as .002" to see how much improvement in velocity I would realize and the difference before/after over the chronograph was exactly 000FPS.

I was curious about what (if any) increase there would be in velocity so that's good to know.

 

[stansdds]

Basically, you have a barrel-cylinder gap of around 0.009", which is within S&W limits, and end shake of around 0.002", which is also within S&W limits. Nothing really to worry about unless you experience bullet spitting from the gap.
Since you mentioned the relationship between velocity and the barrel-cylinder gap, you can read about an experiment at this link.
BBTI - Ballistics by the Inch :: Cylinder Gap