How To Fit New Cylinder To J Frame 942

HEADKNOCKER

HEADKNOCKER

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I have this idea of fitting a 940-1 cylinder to my 642 No Dash.. To Make a 942..
I want to fit it so that the yolk is undisturbed so the factory 38spl cylinder can be swapped back & forth..
Just wonder how this could be done? I assume the bottom of the cylinder were the yoke rides would have to be cut to exactly the dimentions needed while getting propper headspace & barrel cylinder gap..
The cylinder comes with the ratchet but I would also have to aquire a ejector rod & center rod + springs to acomplish this feat..
Any advise that can be given would be helpfull..
I know then the ratchet would need to be fit to the existing hand as well..
I know that if the cylinder has some end shake I could shim it but what if there is none & the cylinder won't close then what??
Thanks in advance for any replies..
Gary/Hk
 
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The 940-1 Cylinder is shorter than the 642 cylinder be a few 100ds, So it will close, BUT will it function properly? It may be OK when I checked my NIB J Frames, It went swimmingly well about 25% of the time.
As far as the extractor rod, Try it,,, I had one stick the cylinder shut, And needed to remove a tad of material from the knurled end to fit up to my NIB 649 no dash, Than all was well.
You may be surprised at how parts can be exchanged and work with very little hand fitting.
I used no shims and found that even if the cylinder fits well, You may need a longer firing pin.
The 940s cylinders are shorter on the star end,,, If memory serves 2/100ds shorter but will need to measure what I have first.
On my 649 all was well, BUT on my Model 60-2 I had a light primer strike every 2-3 cylinders worth with 9mm (reloads) but 100% with 38 supers and 9x23s,,, May have been the reloads.
If you lived closer, We could sit down with a bunch of J frames and see what happens!
I will try to get the exact measurements later today!
Peter
 
Thanks pred!!
What I was trying to get answered is how would one go about making it so the two cylinders could be swaped?
I don't see any way you could measure the depth of the hole in the cylinder were the yolk bottoms out..
I do see however that you could measure from were the ejector touches the recoil plate to the area were the forcing cone would be against the cylinder..Minus the cylinder gap..
Just something I haven't done & wondered how a guy would go about doing it propperly..
Thanks in advance to any & all replies, Even if there Smart*** replies from a few people around here..
You Know Who You Are!!
Gary/Hk
 
While I've never swapped to a 9MM cylinder, I have fitted several cylinders to J,K&N frames. (a convertible 1917 in .45LC, .45ACP and .455 Webley for instance). It's trial and error. Lots of taking apart and putting back together. Right now I'm working on fitting a Model 36 cylinder and barrel to a true I frame Terrier. I had to shorten the cylinder by about 1/10th of an inch and it's taking lots of slow filing to get everything to fit without going too far. Just dry fit the 940 cylinder and see how things look.
Chris
 
Thanks!!
It looks like I'm going to get to try this convertion on my 642..
I have a 940-1s complete cylinder assembly coming in the mail from a forum member..
I'm now thinking that if the yolk is too long for the new cylinder then it'll have to be trimmed & then the amount that was removed would have to be shimmed into the old cylinder so it could be swapped with perfect end shake..
Then the ratchet would have to to be fit to the hand..
Thanks for any & all info..
Gary/Hk
 
HEADKNOCKER said:
Thanks pred!!
I don't see any way you could measure the depth of the hole in the cylinder were the yolk bottoms out..Gary/Hk
Click to expand...

Machinist have measuring tools called depth micrometers http://www.amazon.com/dp/B001C7OGE6...e=asn&creative=380341&creativeASIN=B001C7OGE6 that will measure the cylinders easily. Another way a home hobbyist can measure it is with the tail end of a caliper or vernier. Starrett 6" Range 0.0005" Resolution Electronic Caliper | Rutland Tool This won't be as accurate but close enough for "government" work. :)
 
Last edited:
942 Ready For The Range

Well I got the 942 together..:D
First off the ejector rod & center pin that I aquired was for the magnum lenth cylinder so I had to mill them down, the center pin was titainium BTW..
Then after getting the cylinder fit with a .005" cylinder gap I had to file the ratchet.. I did this one at a time file very slowly & reassemble try till the hand was tight against the ratchets edge.. Took a couple of hours but the project is now ready for the range..
But now I can change from 38spl to 9mm para with just an end shake screw removal swap cylinder & reassemble..
I feel confident that this will be a success..
Now we'll have to see if it'll have the sticking case situation..
I have the "New Hones" waiting to try them..
Thanks a bunch 500MN
Gary/Hk
 
Looks the same except for the extra gap at the front of the cylinder..
Nice match up as far as finish from the cylinder to crane to barrel..
Gary/Hk
 
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