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9mm Cylinder - how much gap is too much?

This is a discussion on 9mm Cylinder - how much gap is too much? within the Gunsmithing forums, part of the Firearm Forum category; I just purchased a 9mm cylinder for my .357 Blackhawk. It fit right in, but has a tiny bit of fore-aft play. When set all ...


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Old February 10th, 2017, 04:36 PM   #1
 
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9mm Cylinder - how much gap is too much?

I just purchased a 9mm cylinder for my .357 Blackhawk.

It fit right in, but has a tiny bit of fore-aft play. When set all the way back, there remains a 0.0132" gap between the cylinder face and the barrel. The .357 cylinder has a gap of only around 0.0041".

Is it possible to place a shim on the pawl end of the cylinder, or would that interfere with the operation?

Or, should I just try it out and see how much blow-by I get through the gap?

Thank you in advance.

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Old February 10th, 2017, 04:45 PM   #2
 
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Did you check that gap with 9mm cases of the proper length in the chambers?
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Old February 10th, 2017, 05:17 PM   #3
 
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.004 to .006 is normal.
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Old February 10th, 2017, 05:34 PM   #4
 
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Quote:
Originally Posted by firescout View Post
Did you check that gap with 9mm cases of the proper length in the chambers?
I did not. I did load it up with loaded rounds and it did seem to tighten up slightly. However, of course, I didn't want to mess around with it much while loaded. I don't reload 9mm (yet?), so don't have empty sized cases.

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Old February 10th, 2017, 05:35 PM   #5
 
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.004 to .006 is normal.
Ok, thank you.

I'll just take it to the range and try it out as-is.

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Old February 11th, 2017, 10:12 AM   #6
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.004~.008" is normal with .006" being optimum. Your .013" gap is about double. I'll bet there is a considerable amount of endshake too. Not a good thing!
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Old February 11th, 2017, 10:31 AM   #7
 
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.004~.008" is normal with .006" being optimum. Your .013" gap is about double. I'll bet there is a considerable amount of endshake too. Not a good thing!
Don't know what I was thinking in my reply to bwinters...

Thanks for the response.

Is there a way to remedy this? Can I slip a shim on the pawl end of the cylinder?

Thanks.

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Old February 11th, 2017, 11:02 AM   #8
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Aqualung, Nope, you're pretty much screwed when you have a gap that wide. Shims on the back end of the cylinder don't work because there has to be access for the hand to grab a ratchet and rotate the cylinder. Pull the cylinder and look at the recoil shield and you will see what I mean.

Your 357 Mag cylinder sounds like it fits about perfect so there's no way I would modify the frame to make the 9mm cylinder fit because it would hose the 357 cylinder.

Sell the 9mm cylinder and try again .... mostly it's luck of the draw .... about 50% will fit OK.
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Old February 11th, 2017, 11:56 AM   #9
 
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Originally Posted by Iowegan View Post
Aqualung, Nope, you're pretty much screwed when you have a gap that wide. Shims on the back end of the cylinder don't work because there has to be access for the hand to grab a ratchet and rotate the cylinder. Pull the cylinder and look at the recoil shield and you will see what I mean.

Your 357 Mag cylinder sounds like it fits about perfect so there's no way I would modify the frame to make the 9mm cylinder fit because it would hose the 357 cylinder.

Sell the 9mm cylinder and try again .... mostly it's luck of the draw .... about 50% will fit OK.
That's bad news, then. Youre right, I'm not about to alter my .357 frame.

Thanks for the input.

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Old February 11th, 2017, 05:27 PM   #10
 
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...Sell the 9mm cylinder and try again .... mostly it's luck of the draw .... about 50% will fit OK.
Is that better than having a gunsmith build up the ratchet with weld, and then machine it off the appropriate amount to fit the cylinder to the frame?
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Old February 11th, 2017, 06:02 PM   #11
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firescout, It's possible to do what you said but the results are seldom good. Seems the cylinder gets bashed into the recoil shield with about 35k psi every time you fire shot. If the weld is too soft, it will peen the ratchet column and if it is too hard, it will crack it. Further, it's impossible to weld an extension on the ratchet column without affecting the heat treated cylinder so you may just find the cylinder kabooms on the first shot. There aren't too many places on a gun where I would risk welding .... especially anything related to the cylinder.

All is not lost .... somewhere there is a Blackhawk that will fit the OP's cylinder and somewhere there's a 9mm cylinder that will fit the OP's Blackhawk. It's just a matter of finding those matches.
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