640 to 940 conversion?
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HEADKNOCKER
Member
If your "LUCKY" enough to find a 940 or 940-1 cylinder it "Should" be fittable to the 640 No Dash as it has the "Short" cylinder, Non Magnum J Frame..
I scored a 940-1 cylinder from a forum member in a trade & fitted it to my 642 No Dash creating the fabled one off Model 942 9mm Airweight..
First the cylinder will have to "Time" Correctly & have the same "Endshake" which can be adjusted with Power Customs End Shake Shims or Yolk Stretch..
On my convertion I had to file the ratchet as the cylinder was new, I also had to fit the center pin of the cylinder as well as the ejector rod, My 940-1 cylinder had end shake in the 642 frame so I shimmed the 940-1 cylinder to fit the frame, I added 2 x .002" shims, If it would have been the other way I would have had to trim the yolk to fit the 940 cylinder & then shim the 642 cylinder..
Then you also have barrel/cylinder gap which on mine came out to .004"-.005"..
There were 640 No dashes with the "CEN" prefix that were marked in the frame window as to handle +P+ 38 Specials..
As far as if your 640s metal is up to the 9mm preasures, I'll only speculate as I know of another guy here Pred who put a 940 cylinder into a M60 & had the cylinder bored to 9x23 & had great success with it & was planning on doing another on a 649/638 Bodygaurd?
Each cylinder is different & if you luck out to finding a pre cut 940 cylinder & it fits your frame, You'll be lucky, Pred was.. He told me it timed perfectly..WOW!!
With the price of 38/357 it seems like a 9mm snub would be the ticket & maybe S&W will do something about it..
The 940s suffered from extraction problems mostly due to the 9mms tapered case & variouse ammo specs, Some will function & extract fine others well Don't..
Alot of early 940s cylinders are "ROUGH" as they must have had a problem with thier tappered reamer? & they have alot of problems extracting spent cases, Others are perfect & have No Troubles, I had my first 940s cylinder reamed to 38 Super & have had very little trouble with it "Except" for Winchester White Box Value Pack 9mm.
All others I have tried extract just fine with a small rap on the ejector rod..
I have a set of cylinder hones, Donated by the Forum BTW, that "CAN" cure some/most extraction problems due to a rough chamber.
You might be better off just trying to Buy a 940..
If your 640 is "MINTY" I'm not sure what I would do?? Hmmmm??
Good Luck with your Quest!!
Gary/Hk
Model 642 Airweight Converted to 9mm Via 940-1 Cylinder
Model 940 & Model 642/942 Airweight 9mm
I scored a 940-1 cylinder from a forum member in a trade & fitted it to my 642 No Dash creating the fabled one off Model 942 9mm Airweight..
First the cylinder will have to "Time" Correctly & have the same "Endshake" which can be adjusted with Power Customs End Shake Shims or Yolk Stretch..
On my convertion I had to file the ratchet as the cylinder was new, I also had to fit the center pin of the cylinder as well as the ejector rod, My 940-1 cylinder had end shake in the 642 frame so I shimmed the 940-1 cylinder to fit the frame, I added 2 x .002" shims, If it would have been the other way I would have had to trim the yolk to fit the 940 cylinder & then shim the 642 cylinder..
Then you also have barrel/cylinder gap which on mine came out to .004"-.005"..
There were 640 No dashes with the "CEN" prefix that were marked in the frame window as to handle +P+ 38 Specials..
As far as if your 640s metal is up to the 9mm preasures, I'll only speculate as I know of another guy here Pred who put a 940 cylinder into a M60 & had the cylinder bored to 9x23 & had great success with it & was planning on doing another on a 649/638 Bodygaurd?
Each cylinder is different & if you luck out to finding a pre cut 940 cylinder & it fits your frame, You'll be lucky, Pred was.. He told me it timed perfectly..WOW!!
With the price of 38/357 it seems like a 9mm snub would be the ticket & maybe S&W will do something about it..
The 940s suffered from extraction problems mostly due to the 9mms tapered case & variouse ammo specs, Some will function & extract fine others well Don't..
Alot of early 940s cylinders are "ROUGH" as they must have had a problem with thier tappered reamer? & they have alot of problems extracting spent cases, Others are perfect & have No Troubles, I had my first 940s cylinder reamed to 38 Super & have had very little trouble with it "Except" for Winchester White Box Value Pack 9mm.
All others I have tried extract just fine with a small rap on the ejector rod..
I have a set of cylinder hones, Donated by the Forum BTW, that "CAN" cure some/most extraction problems due to a rough chamber.
You might be better off just trying to Buy a 940..
If your 640 is "MINTY" I'm not sure what I would do?? Hmmmm??
Good Luck with your Quest!!
Gary/Hk
Model 642 Airweight Converted to 9mm Via 940-1 Cylinder
Model 940 & Model 642/942 Airweight 9mm
OH these threads bother me.
I still am sitting on all these unfired parts...
Maybe one day I will get around to building a real 949.
If it's a Small cylinder window (Non magnum) sized, The 940 cylinder can be made to fit like Gary said!
Peter
I still am sitting on all these unfired parts...
Maybe one day I will get around to building a real 949.
If it's a Small cylinder window (Non magnum) sized, The 940 cylinder can be made to fit like Gary said!
Peter
You can get a 940 cylinder from Brownell's for about $125 +/-. I bought one to fit to my 637 but it was the older style short cylinder and didn't fit, my 637 has the newer longer frame. I returned it to Brownell's but I'd imagine they still have them in stock.
It seems as though the only 940 cylinders available are the 940 and 940-1s = short window.
The 940-2 was on the magnum sized frames and I have never seen any of those cylinders available.
You may see a cylinder listed as "New style"
Be assured that it is the shorter but with the new style extractor star.
Peter
The 940-2 was on the magnum sized frames and I have never seen any of those cylinders available.
You may see a cylinder listed as "New style"
Be assured that it is the shorter but with the new style extractor star.
Peter
safearm
US Veteran
I went through the same decisions. I had a 637 converted to 9mm moon clips by TK Custom, then found a 940-1 cylinder. I was planning on purchasing a used LNIB 640 to convert, but the gun shop was burglarized and that was one of the guns taken. I then lucked out and traded the cylinder to Gary, and located a 940 on the forum that had been tuned up by S&W. The J frame 9mm bug bites hard!
The veil of shame hangs heavy upon me. I have had two 940's in the past and let them go. I dont want to pay twice what I got them for. So this project seems interesting and cheaper than coming up with the whole gun.
I don't think it's that bad, a lot of guys think the 940 kicks hard, but honestly, to me, it feels the same as it did with .38spl +P before the conversion. My carry load is Federal 9BPLE +P+, it's a bit sharper than standard pressure ammo but still way less recoil and muzzle blast than a .357 snubby. Fast doubles and triples are easy to keep on target.
Thanks WC145. I have found some articles that say it was a drop in part. Some other say it needed some minor work. I am excited and have placed an order for two.
Headknocker thanks for your offer on the cylinder smoother. I may have to take you up on that.
Headknocker thanks for your offer on the cylinder smoother. I may have to take you up on that.
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HEADKNOCKER
Member
The 940 and the 940-1 may not be any different at all.
The cylinder you will get will have the new style extractor in it, No issue there with fitting to any J frame.
It will drop in some J frames and not others,
I tried the ones I have in 4 or 5 of my J frames and they were OK ready to go in 2 of them I believe.
NOW look up Dave Manson here on the board and send your cylinders or just one straight to him and have him ream them out to 9x23, That way you will be able to shoot 9mm/38 super and 9x23 for 357 like balistics,
And you can always put the original cylinder back on and shoot 38 special.
Plus he will chamfor the charge holes at a very reasonable cost.
I sent him two of them before I did my conversion...
Now shooting the 38 super is just dandy to me,,, Good shooter and a bit stouter than the 38 special but not like the 9x23.
Here is a pic of my universal ammo shooter model 60 converted to a "960"
Great carry gun that I can practice with whatever ammo is cheapest or most plentiful at the time.
I have some 38 super+P for CC.
Peter
Wee Hooker
Member
Oh why oh why can't S&W bring back a lightweight 9mm J frame? It just makes sense.
-good BUG for those who already own a 9mm
-Comparable performance to 38 spl
-positive extraction of ALL spent cases
-reload takes up less room than speedloader full of 38's in your pocket.
I still wonder why the market wasn't there.
-good BUG for those who already own a 9mm
-Comparable performance to 38 spl
-positive extraction of ALL spent cases
-reload takes up less room than speedloader full of 38's in your pocket.
I still wonder why the market wasn't there.
JNewell
Member
Cylinders are never a drop-in part. There are fitting issues related to both timing and basic dimensionality (headspace, endplay, b/c gap, etc.).
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