If I want better carryup on all cylinders of my 640, is the answer a wider hand? If I measure the old hand, how do you go about ordering a hand by size?
Thanks in advance.

First,

Describe for us what is going on and why you think you need better carry-up...also, describe your cleaning procedure and cleaning agents used, and approx. how many rounds you've put through the gun. Describe any timing issues that you are finding... What year was your 640 produced?

giz

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As far as I know, there are only two kinds of hands: stock and the "wide" hand. If I recall right, the wider hand is about .005" wider than stock. It's possible a new stock hand will improve your carry up and not require a wider hand if the wear isn't too bad..

Edit: Kuhnhausen says stock hands are .092" - .094", and the wide ones run about .095" to .097". The wide ones I got were closer to .099" by my micrometer.

The answer is a wider hand. The problem is that what size hand you get is potluck. Std hands seem to have about a .003" thickness range (variance).

It is a 640 no dash, and the hammer drops, almost at the same time the cyl. stop drops into its notch. It probably has about 200 rounds through it, and I guess it is from the early 90s.
The cyl. is always locked before the hammer drops, but it is very close.
I own many S&W revolvers, and know what good carryup feels like. I was just wondering how to order a new hand other than stock, and where to get it.
Also, if the hand is too tight it should never be filed? Correct? Only the frame?

That's my recollection, you file the window slightly winder with a special file designed just for that purpose.

egunparts, aka Numrich, usually carries the wide hands. As far as I know S&W sells them also without a hassle.

OK, thanks for answering me...

It's been my experience that cleaning solvents sometimes get brushed into the hand window in the recoil shield while the gun is being held with the barrel pointed upward. This tends to build up a layer of congealed oils and fouling in the window behind the recoil shield. As this layer builds up and dries, it will hold the portion of the hand that rides in that slot back. Basically, it is riding on a layer of congealed and hardened fouling. It cause the hands beak to release early. Simply breaking the gun down and scrubbing this area with a non-chlorinated brake spay cleaner....generally returns the gun to normal timing....saving a good deal of gunsmithing bill and replacement of parts plus fitment....

To answer your other question, I tend to hone the riding surface(s) of the hand if I need more forward or less lateral engagement. I've never needed to file a frame


giz

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There will probably be some disagreement but if I have a hand that is slightly too thick I stone the left side of the tip of the hand. The area that actually engages the ratchets. Less chance of screwing up and damage done only to the hand if you do. I will only file the window if the hand is too thick to fit in the window. Thinning the hand is still preferable, even then.

A good rule taught in Armorer School is to always work on the cheapest part. If the new hand binds all the chambers, then work on the side of the hand that engages the ratchets. To get that far, if the hand is tight in the hand window, then you can open this window on the frame side, never toward the sideplate side. When the hand fits the "shortest" ratchets, then work on the remaining ones until they all carry up at the same relative time. Then we are all back to working in harmony.

Generally, a replacement hand will work pretty will if it is about .002 wider than the old one that does not carry up soon enough. If it is just barely short, then .001 might be enough. That reduces that chance that the hand window needs to be opened, or the new hand needs to be stoned. The ratchet side of the hand is hardened, so it takes a little work to fit it.

Me too. The hand is very hard steel with a sharp edge, it widens the frame slot over time on the right hand edge. I would never cut metal off the frame. hand costs about $10, frame cost is....? guess which one gets filed.

Shave the hand lightly on the left upper edge if it binds passing by the ratchet until you have just enough clearance.

amen....

+1, that bears repeating: the hand wears the right hand side of the frame window, so NEVER cut on that edge. File the other side if you really must, never the right edge.

+1, that's the way to get the carry up balanced.

I'd offer that while some folks enjoy engaging in a bit of kitchen-table gunsmithing, that carry up/'timing' issues are really more in the realm of what ought to be handled by someone who has some knowledge and experience in diagnosing and correcting them, which usually means seeking the services of a gunsmith or the factory (unless you know a local S&W trained armorer).

Also, checking carry up in a new model S&W revolver (meaning the models which use the new extractor design which isn't held in position by pins mounted to the cylinder under it) requires the use of properly sized DUMMY rounds in the charge holes. The new style extractor is held in position by the cases of the ammunition loaded in the charge holes during live fire (and dummy rounds during bench checks), instead of being held in place by the pins in the old model revolver cylinders. You're not going to be able to accurately check the carry up in a new model S&W revolver without using dummy rounds.

FWIW, the recommended correction in the armorer's manual for a properly diagnosed carry up problem is to replace the hand with a new one (larger).

That may create a 'long ratchet' condition, though. (Think of one, or more, of the extractor ratchets trying to occupy the same space as the hand at the same time.) If so, the specific ratchet(s) will have to be corrected (filed). This requires judicious and proper filing, and unless someone knows what they're doing it's a fairly easy way to ruin a ratchet (and therefore the extractor).

If the larger hand doesn't correct the carry up issue then it's recommended the extractor be replaced, which involves cutting a new one. S&W makes their cutting tools by welding an arm (lever) to the appropriate model trigger and using a hardened cutting hand. The cutting tools are included in armorer revolver tool kits or can be ordered separately.

On a related note, cutting the ratchets on a new extractor requires dummy rounds loaded into the charge holes to position the ratchets (and hold them) for cutting as they will be positioned when engaging the hand during actual firing, or else the extractor's ratchets may not be cut right.

Oversize hands can be ordered from the factory. I ordered a couple of them to try and tighten up a J-frame's carry up once. I can't remember the sizes when they were gauged but there was at least a couple of thousandths difference among each of the separate hands once I had them in front of me on the bench.

In my case the next size up still didn't provide what I felt was acceptable carry up on all the charge holes, and the next one up from that one was too big to easily move within the window. Not wanting to adjust the frame window I cut a new extractor (which requires the use of the cutting arm) and it corrected the carry up when using the new extractor with the original standard hand. I also paid attention in the armorer class when it was recommended that the least expensive part be filed or adjusted.

Checking carry up in a DAO revolver involves slowly pulling the trigger to the rear so the cylinder stop engages the stop notch in the cylinder. (This doesn’t mean pulling the trigger sloooooowwly, though, nor does it involve touching the cylinder to ‘create drag’.) The cylinder stop should engage the cylinder stop notch before the hammer falls in DA (and before full cock in guns with SA capability).

If you believe your 640 doesn’t exhibit normal carry up why not ask the opinion of a gunsmith or call the factory and ask for their advice?

I've been told by at least a couple of factory folks that the newer model revolvers often exhibit carry up where the cylinder stop engages the stop notch in the cylinder just barely before the hammer falls, and that it's considered within spec even if it's very close, as long as the cylinder stop/stop notch engagement occurs before the hammer actually falls.

I’m neither a licensed gunsmith nor a factory technician, but only an armorer, and obviously I can’t know what’s happening with your particular revolver since I’m not examining it. I’m just offering this info for the sake of discussion.

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