I have a 940 with extraction issues. I tried having someone hone the charge holes and that improved the sticking but did not fix the problem. It was still very difficult to extract the spent casings. Time goes by and now I have sent the gum for repair to a well known shop that does cylinder work. They machined the charge holes and they look very smooth now but unfortunately, the sticking only got marginally better. Now I'm looking for opinions on next steps. I discussed the issue with the shop and they said something like - I took a lot off of the cylinder and I'm concerned if I take much more off the cases will bulge. He said to send it back and he would take more off but I'm not sure that's what I should do.

Note that when the unfired rounds go into the cylinder they extract and go back in without any sticking. Basically, they drop right in. After firing, I cannot extract the cases without forcing the extractor. It can be done by hand, but I would never rely on this gun for SD unless I never planned on a reload. Good news is that it does go bang every time.

Anyway, it seems like the cases are indeed expanding and causing the extraction problem. None of the cases split. I used some cheap range ammo and some Speer Gold Dot SD ammo and got the same results with both.

So between honing and machining, the smoothness of the charge holes does not appear to be the issue. I'd appreciate some conversation about what might be the best next step. I'm also curious if there is any way to get the factory specs on the cylinder to see if the holes are beyond specs now of if there is still room for more machining. I'm also wondering if the machining has already caused the problem. I thought I read once that the charge holes in a 940 are tapered. I'm not sure if they are any longer, but I doubt it. It does appear that the catch in the extraction is at the base of the spent case (so at the top of the charge hole).

Let me know what you think. Thank you.

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18-4, 15-4

First, have you ever looked at a 9mm case/cartridge? Is it tapered? Of course it is, and so are the charge holes. Are the fired cases still tapered? If so then the charge holes are!

What do I think? That this issue should have been addressed with S&W that would have repaired the revolver at no cost under warrantee, instead of spending money sending it to a shop that may not have any better idea what the issue is than you do. And spending probably well over $100 in the process for what could have been free!

I realize that there is some interest in semi-automatic pistol cartridges in revolvers, but I have never understood why! There are far more problems with this concept than when using normal rimmed cartridges intended for revolvers.

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Gunsmithing since 1961

When I fixed my 940 I used a borrowed chamber hone. It is a special set of ceramic ends set on spring loaded centers for the particular caliber. Using the correct honing oil and a cordless drill only on slow to medium speeds will polish the chambers. It will take a good hour of working on it to get the chambers smooth enough. Now, the empty moon clip won't just drop out, but it will extract with minimal effort on the ejector rod. If someone has already been "cutting" on the cylinder, I would recommend sending back to S&W to "fix" it.

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H Richard
SWCA1967 SWHF244

Clarification. I have already sent the revolver back to S&W and their response was to offer me another gun since the 940 is no longer manufactured. Because I wanted to keep the 940, I hooked up with a guy on this forum who had the hones and he did the honing for me. That helped a lot, but still not what I would call a fully functioning gun. Then I sent it to a shop for evaluation and they machined the cylinder. I don't want to mention the shop, but they are spoken of in high regard on this forum. The charge holes were a mess when I first got the gun and now they are very smooth.

What I'm hoping is that there may be someone who can offer any other ideas or comments on what might be the next best step.

I appreciate the idea to look at the cases before and after to validate the tapering. One of my thoughts is that the charge holes are not tapered and maybe having the shop open up the top of the charge hole just a little bit may work. Maybe even just some more honing - similar to a slight chamfer.

In the end, I'd really like to fix the gun, but if I can't, my downside is that I send it back to S&W and, assuming their offer is still good, they will send me a new 640 or sell it to someone for parts or who has a cylinder (a number of them were sold to turn 640's into 9mm's).

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18-4, 15-4

I'm not that familiar with the 940 so forgive me if I'm way off the mark here.

I'm assuming it uses moon clips. Is there any possibility the moon clips could be causing or exacerbating extraction issues?

It does use moon clips and I did think of that, but I'm pretty sure the moon clips are not the problem. After firing, I put a spent case in each of the charge holes and there was resistance. I'm sure the fact that the moon clip is connecting all the cases together doesn't help but it is a moon clip gun and should work with the clips I have - all new and bought from Ranch Products (who I think makes them for S&W).

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18-4, 15-4

Jerry, if I am correct you have had this back to S&W but they did nothing and returned to you. Then to a good gunsmith who machined something in the cylinder, but there are still problems. Did the gunsmith machine some off the interior of the cylinder face to allow the moon clips to seat a little deeper? If so did he also re-cut the chambers with a finishing reamer to set the step for the head space a little deeper also? Is there a possibility that rounds/brass is bumping on the step and keeping the rounds from fully seating without more oomph? That could also keep the case heads a little high and cause drag on the recoil shield.

I was just out with my 940 yesterday, and put about 200 rounds through it. While the rounds/clip don't just drop out it only takes a little pop with the heel of my off-hand to get them out. With a 940 you don't ever expect the rounds to just drop out. The 9mm works at too high a pressure for that.

Tom Kibler at TK Custom is an expert doing moon clip conversions and would be the most qualified person to figure this out.
Welcome to TK Custom.com & Moonclips.com

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H Richard
SWCA1967 SWHF244