View Full Version : Sticking Chambers S&W 940 9mm What To Do?

October 15, 2006, 08:30 PM
Well I got around to shooting My 940 No Dash yesterday at the range..
It's very accurate & has a buttery smooth trigger & The Uncle Mikes Grips feel great..
This Snub realy is a tac driver for it's size, & was dead on..
On the down side this 940 is plagued with the sticking case syndrome that I read about while doing searches on 940s..
I had the plastic mini mallet with me, I wouldn't have got any of the spent cases out without it, Nickle/Chrome cases came out a bit easier but the Winchester white box was stuck tight..Without the Moon Clips I could easily poke the brass out one at a time with a pencil.
I'm not sure but I believe that the problem is the insides of the cylinders has rough mill marks..No Smooth!!
I also have a Ruger SP101 9mm & it's always been 100% with any ammo I've ever tried, ejecting easily with or without the full moon clips..The Rugers Cylinder is almost smooth inside..
I wonder if a cylinder hone would cure the 940s problem..
Brownell's Cylinder Hone (http://www.brownells.com/aspx/NS/store/productdetail.aspx?p=649&s=)
I sure hoped this 940 wouldn't suffer from this trouble, It's probobly why they discontinued it.
I may have to call S&W
What do You all think? What Should I Do??
I'm gonna try & get a few pics of the inside of both The Ruger & S&Ws 9mm cylinders for you all to see..
Well anyway it's a Tac Driver but can't be used as a self defence carry piece with chambers like this..
The only cylinders I've seen that were rougher than this were on a Dan Wesson 15-2, It also had the sticking case syndrome too!!
I want this to become one of my carry Pieces..
Here's a few pics, The best I could do, of the cylinders holes of the two different 9mm 5 shot snubbies..
Believe me the S&Ws holes are crude looking..
Thanks Gary
940 Ready For The Range
9mm Cylinders
940 Cylinder
SP101 9mm Cylinder

October 15, 2006, 10:21 PM
The roughness won't help, but most likely the thinner steel (than the Ruger cylinder) is stretching elastically and snapping back under the pressure. That tightens it on the brass. It may be the design was discontinued because it is marginal at 9 mm pressures? Sticking brass is a classic pressure sign in a revolver. I would suggest you consider reloading for this gun so you can reduce the pressure a little. It probably won't need a lot of reduction, just 10% or so. You won't give up much by way of horsepower and can probably make up the stopping power difference with bullet choice; I like cast truncated cones for that.

If you want to get rid of the roughness in the cylinders, you can have them reamed to maximum specification, but that won't help with the wall thickness issue. Besides, you have good accuracy now, and don't really want to mess with it. Instead, let me suggest you find a fine stainless wire brush that you can run in and out to lightly clean the surface off and knock down any high spots. This is generally considered safer than using a hone or a lap, which can inadvertently round the chamber mouths. Ask the folks at cylindersmith.com what brush they use? They don't ream 9 mm cylinders, but whatever brush they use for .38/.357 would work. Once clean, use a hair dryer and a bore mop to apply Shooter Solutions MolyFusion Oil (http://www.shootersolutions.com/molyfusion1.html) to the inside of the chambers. This will make the surface permanently slippery. It won't solve the pressure problem, but will make case extraction easier.

I've used the MolyFusion Oil product on Garand gas cylinders and op-rod piston heads to good effect. Practice on a couple pieces of steel scrap with a Q-tip until you get used to working with it.


October 16, 2006, 12:25 AM
Thanks Unclenick
I have ordered some of the Moly-Fusion & the two grits of 38/357 cylinder Hones & it's oil from Brownell's.. 9mm is slightly larger than 38/357..
I have used Militec-1 in cylinders but have never heard of the Moly-Fusion before, Thanks for that tip!!
After compairing fired cases from both the Ruger & S&W I've come to the conclution that the S&Ws rough cylinder bores are a bit too tight...
I also need to aquire a Go & No-Go gauge for 9mm
Hope this will take care of it..
I also need to aquire a bunch of different ammo types to try in the S&W 940
Range report Due in a few weeks after the goodies arrive..

October 16, 2006, 05:23 PM
Here's a better pic of the rough chambers
All 5 holes look similar, some worse than others..
Do They Need Reaming??
Rough Cylinder

October 18, 2006, 02:48 AM
Unclenick I was told by a few Gurus @ The S&W Forum Not to use any type of lube in the chambers of the 940, They say that if the cylinders are slippery the case won't cling to the clyinder & will push the round back on setoff forcing the ammo & moonclip into the recoil shield locking the revolver up..
There's a few guys there who have tried exactly that & had to hone the lube out..
I have the two Chamber Hones + it's oil for a 38/357 coming from Brownell's
I will try & get several pics as I progress, I will start with the Medium & finish with the Fine, I may also polish each chamber with a patch of Flitz wraped around a mop in a cordless drill as a final polishing step..
I plan on coating the chambers with some ink so I can see were the metal is being removed & checking with a fired case from the gun trying to recreate the size of My Ruger SP101s Cylinder in The S&W 940..
I have the moly-Fusion coming too, But won't use it in the chambers unless all else fails, Thanks for the heads up about this product, It will have many uses..Even thought about taking all the revolver inerds, including springs etc & coating them with it, It might slicken it up just a bit..
When i put this revolver back together I used TW-25B white grease on the inside of the revolver spairingly as not to atract debris & FP-10 on the rest..
It's Buttery Smooth & It's DAO trigger pull is one of the best I've ever seen, much better than my S&W 442 Airweight or even my 1952 Pre 40 Centennial Lemon Squeezer, Made Back when most smithing was done by hand..
Thanks For The suggestions & Keep Em Comin!!

October 18, 2006, 11:28 PM
I aquired the Flex-Hones From Brownell's Today!!
Will probobly get around to smoothing it up later this week..
Range Report Due!!

October 18, 2006, 11:55 PM
Go slowly and take plenty of time and lots of lube. The not lubing the cylinder is good if the charge holes are on the loose side. Try it once to see if it helps, if not clean very good and it should be okay.

October 19, 2006, 10:37 PM
I'm honing the cylinder now..
It looks alot better but the deep grooves aren't going to be completely removed..
The Moly-Fusion hasn't came yet, I may try it after a range test dry to see what's going on..
Thanks again..
Gary B92

Harry Bonar
October 22, 2006, 10:44 AM
Dear Sir:
It will not hurt anything to hone out those cylinders - I've done it many times with some 240 grit paper around a dowell in my drill press - your approach is good! I am suprised at Smith - they generally never need smoothed up - but.
I don't think you'll ever hurt either cylinder but I'd also LIGHTLY chamfer the entrnce holes also - should give you NO trouble.
Harry B.

October 22, 2006, 12:41 PM
Thanks Harry!!
I've used both hones & polished them all with Flitz, They look alot better but aren't completely smooth, To get that the holes would be too big..
I thought of beveling the charge holes but haven't pursued that yet..
I'll Try an get some good pics of the chambers now..
Range Test Due ASAP :D

October 22, 2006, 04:24 PM
Have you contacted S&W?

They are very receptive and willing to make it right at no cost to you.

However, once you modify/take abrasives to the cylinder, I would not be surprised if they were somewhat less so.

Your call, but I would let S&W take a crack at it first.

October 22, 2006, 07:35 PM
Over at the S&W Forum there are several guys who have sent thier 940s to them for sticking cases, They get them back & you guessed it, It still does it.
I can't realy put my finger on it yet but I'm guessing the cylinders holes are just too tight, The Ruger SP101 9mm works perfectly, And if the other S&W 940s cylinders holes look like mine we now know why...
A new cylinder costs about $135.00 if they have them..
I may contact them after a few more range tests if the problem persists..
I hope I'm onto the cure..

October 22, 2006, 08:28 PM
Honing the cylinders will help a lot. I've had to do it on my 625s. Do not use Moly Fusion inside the Cylinder. I've talked to Johnathan, the owner of the company and he does not suggest doing it on the cylinders, in any chamber or on the internals of a revolver because it is so slick it will affect the timing.

I've used Moly Fusion as recommended, in my barrels on all my revolvers, and my 22s . It helps accuracy so much I can't see not using it.

October 22, 2006, 09:08 PM
Still Haven't recieved the Moly-Fusion Yet?
I won't use it in the cylinder but might in time try it in the barrel as you suggested.. Maybe even on My Ruger MKII..
You say it's so slick that It'll mess with the timing on a revolver?? WOW!! Must be some super slick stuff.. Or Just like Militec-1..

October 29, 2006, 12:03 AM
Thought I'd Share Another close up of the Cylinder After honing, It looks alot better, This is the worst cylinder as the other came completely smooth..
Started with 220 on a sanding drum stick then 400, 600 & 1500 grit silica carbide with Cutting Oil, Then Crocus Smooth , Then the two Cylinder Hones & Finaly polished with Flitz..
Here's the Before & After of the Same Cylinder, Sorry about the pics but it's the best my old camera could do with an eye loupe taped to it's lens..
Looks Alot Better!!

October 29, 2006, 06:10 PM
Well I took the 940 & my SP101 9mm to Bluegrass Armoury this afternoon..
I started with Remington 115gr HPs Brass Case & shot 85 rounds of it without a sticky case one..
When I swiched over to Winchester White Box it took about three or four cylinder fulls before the rounds were stuck tight, I taped the end of the ejector rod with my nylon hammer & they came free,I also assume the WWB ammo is very dirty & caused most of the trouble but the rest of my WWB was shot by my SP101 with no trouble at all..
I had the range master looking me over as I was doing speed reloads with both the 940 & SP got em both nice & Hot!!
I believe I've got it right were I want it & kept 15 rounds of that ammo for carry Till I aquire some heavier +P 147gr nickle plated Spear Gold Dots..
More Range Results needed with lots of various ammos..
The 940s A Carry Piece Now!!!

November 25, 2006, 12:53 AM
Well after todays range setion the 940 is one of my favorite concealed carry guns..
I carried it for 12+ hours today in my newly aquired Rafter S Sharkskin Holster
It ran 100% with everything I fed it, They were all brass case standard velocity 9mms
I put a #8 Wolff hammer spring & a #15 rebound spring in a few days back, I believe it actualy helped with the case sticking problem plus made the trigger pull a bit lighter with a more snappy trigger return..
As a compairison I shot it side by side with my 442-2 & will have to say that the standard 9mm rounds do have more recoil in the 940 than +Ps in my Airweight, The bigger covered backstrap grip of the Uncle Mike Combat helps alot.
The 940 is dead on & deadly accurate
Moved to the top of the pile of my carry guns
S&W 940 9mm Rafter S Sharkskin Holster

November 25, 2006, 01:03 AM
The only thing that would stop my 940 from working was when using on popular brand of +P ammo...would back that case up tight against the recoil shield, stopping rotation. Probably reason was the very smooth chambers...with so little grip on the walls, cases tended to piston back tightly against the breech.

So I'd not try for a mirrom smooth chamber; that would seem more likely to stup rotation. Too rough a chamber (like yours) and you'll nearly break your hand getting them to eject. Believe you're reached the happy median...just rough enough to retard case set back, but not too rough to let you eject.