Yes, Factory spec is 6 thousandths. On the proudest chamber. That means the gap can be greater on other chambers. Also, the small frame cylinder expands after several cylinders full of rounds. Personally, I prefer .004 on the proudest chamber. Do not force the shim into the gap when measuring. It will push the dedent ball back and the gap will be too small.

 Once you get the feel for 4 or 6 thousandths you can dispense with the shim and hold the gun up to a strong light and eyeball the gap as you cycle the cylinder. It is much faster. If the cylinder is binding or spitting, be sure to unload the gun before you adjust the gap. 

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