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Discussion Starter #1
Hello, I am new to this forum but need some help. I recently purchased a used S&W N frame revolver with 0.020 barrel gap and a lot of blow by. I am trying to find out how to decrease this gap without increasing barrel wobble. Thanks for any help. David.
 

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First of all, welcome to the forum! Second, put your tools back in the toolbox. Third, call S&W and get a shipping label, etc. Reason why is simple. If your measurement of the BC gap is correct, the necessary correction will exceed your abilities unless you are really good w/ a lathe, thread cutting, setting headspace, etc. Sincerely. bruce.
 

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Discussion Starter #4
Thanks Bruce. I am a seasoned machinist and have access to milling machines and lathes, and am able to pick-up on existing threads to thread longer. My mechanical knowledge is sound, but my gun assembly knowledge is limited, like not knowing how to remove the barrel from the frame without warping the frame or destroying the firearm. I prefer to gain knowledge before jumping into the unknown without an informed game plan.
 

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Welcome to the forum. Glad you're addressing this issue. Can you see if it's suffered flame cutting or some other wear?

Is the cylinder itself and it's yoke mount in good shape, or is there end shake or movement? You should start by getting some insight on the S&W revolver from Jerry Kuhnhausen's shop manual.
 

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Discussion Starter #6
Thanks for the link and information. I do not see and flame cutting and not much wear or wobble. The cylinder is recessed and in great shape, I believe the gun was made between 1972- 1974, according to the s/n. I will definitely purchase a book on S&W revolvers.
 

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There is a retired gunsmith on our forum. I would wait for his opinion as to the best way to proceed. I am with Bruce. Send it back to S&W if they will work on it.
 

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Welcome to the forum from a retired gunsmith. Correct B/C gap is .004-.008, .020 is definitely excessive. To close it the barrel would need to be removed & the shoulder turned down or the barrel replaced. Turning it down works if it doesn't affect the front lock too much. Because it moved the lock back it can be resolved by shortening the elector rod a few thousandths... unless it's just too much (in your case likely) where a new barrel is needed.
 

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Discussion Starter #9
Thank you for that information. It looks like the front lock would not be a problem as long as only enough material is removed to shorten it by 1 thread pitch, so it can be indexed properly.
 

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I don't have any advice to offer, this is out of my league, but I do have a question? What would cause such a gap? Would it have had to always been like this or is there something that will cause it?
 

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I don't have any advice to offer, this is out of my league, but I do have a question? What would cause such a gap? Would it have had to always been like this or is there something that will cause it?


Unless somebody did a lousy job replacing a barrel I can't think of anything else short of poor quality control @ the factory.
 

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Discussion Starter #13
I have been wondering the same thing. Was someone using it for a parts gun (the rear sight is missing)??? Does the cylinder color really match the rest of the gun??? Either way, I purchased it, now it is mine. What to do next? Send it off or take it to a local gunsmith, OR, do I use it as a learning tool to test my (supposed) abilities? I am always willing and wanting to learn, and extend my knowledge, ability, and skill level.
 

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If you have a mill you could make the jig & wrench, however if you're not familiar w/ gun work you'll save a bundle hiring it done. How about a picture to see the difference in frame/cylinder? Was the sight removed for a scope mount? Pictures can tell a lot.
 

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Doesn't look like a parts gun to me, I think someone had a scope on it @ some point. I'd fix it... finding sights can get interesting.
 

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Discussion Starter #19
I actually found a rear sight at USA Guns and Gear, that I will get after repairing the problem. Thanks to All for the information and suggestions on my situation.
 
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