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AR15.COM
12/28/2006 8:42:10 PM EDT
I am having problems w/ a new S&W 640 ( J-frame, concealed hammer) Centennial. Sometimes when the trigger is pulled the cylinder does not advance resulting in a misfire.  Local gunsmith inspected and said barrel and cylinder may be binding and there is some end shake.  Can someone explain end shake for me.

I have contacted S&W to do repairs, awaiting shipping authorization.

Thanks
12/29/2006 1:49:22 AM EDT
[#1]
In simplest terms, "endshake" is the forward / backward "play" in your cylinder when it is closed and locked in place. Pretty much impossible to have zero endshake on a production revolver since the parts...obviously...must move, and it must be affordable, so there is a range of acceptable tolerances within which the gun should work correctly. With too much play, the face of the cylinder can move forward enough to bind on the forcing cone of the barrel.

My guess without seeing your revolver is that endshake is not your problem, but that IS just a guess. If you have not shipped it yet, try loosening the lower sideplate screw about 1/2-3/4 turn and see if it still binds. (Can you replicate the problem with an empty gun?)

You have done the right thing by contacting S&W, and they should get you going with no problems.
12/29/2006 6:17:25 AM EDT
[#2]
Thanks for the info ikor
12/29/2006 8:20:32 AM EDT
[#3]
If it is a new gun, by all means make S&W fix it.  

The endshake and barrel gap are clearance dimensions as ikor said.  The gap is measured between the front of the cylinder and the barrel and should be around .005".  Endshake should be as little as possible without binding.  I use these to set clearances and endshake:

End Shake Bearings