637 hammer cocking for single action question

When I cock the hammer on my new 637 for single action fire it seems to have three distinct characteristics. There are two click noises one after the other as the cylinder rotates. Then there is a final step that I feel as the hammer moves/ is pulled the last 1/4 to1/8 inch. This final step corresponds to the trigger moving to its rear most position. This final step of pulling the hammer back is a tad stiff to get past....not horrible but there is resistance. I'm new to s&w revolvers. Is this normal operation?

I posted this in the general area but am reporting here as perhaps I will get a response.

What you are probably feeling is the hand rubbing the ratchet on the extractor. At the end of the cylinder's cycle, (phase 3) the cylinder fully carries up, and locks in place. As the hand passes by the side of the ratchet at the end of the cycle, there may be significant contact between the side of the hand and the ratchet itself, which can cause the resistance, or "rough spot" you are experiencing. The two clicks you are hearing are from the cylinder stop....normal.

Long ratchets are not uncommon. Not a huge deal unless the hand gets trapped between the ratchet face and the side of the hand window in the frame, which can trap the trigger to the rear, and prevent proper trigger return. In this case the gun should be returned to S&W for service.

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Ret. LE, FA Instr, S&W Armorer

Thanks. I'm not familiar with the terminology I'll have to look it all up. But it sounds like this can be normal?

Long ratchets, if this is the problem, are not desired or considered "normal", and are usually more common in a new revolver.

Ratchets are first cut with a cutting tool fit with a tool fit with a hardened hand. They are then finish cut with a file, by an assembler by hand. Many times, after the initial cut is made, these finish cuts are not deemed necessary by the assembler, and this hand fitting step is passed.

You can verify that the ratchets are causing this by opening the cylinder, holding the thumbpiece to the rear, and then cocking the action. If the resistance at the end of the cycle is gone, then this is most likely the problem.

This issue will be mitigated by putting some rounds through the gun, and/or by dry firing. Although you are not required to do so, I would use snap caps when dry firing. This will help protect the firing pin during this exersize. The dry firing will help "break in" the components, expecially at the contact points, including the hand/ratchet interface.

__________________
Ret. LE, FA Instr, S&W Armorer

I did as you suggested and opened the cylinder and worked the hammer. The resistance disappears. So long rachet it is.

The ratchet or hand? (The part that turns the cylinder) when the hammer is cocked back, sits flush with the frame. I cycled the action about 100 times. It seems smother....maybe. It's not much resistance. I only can feel it if I pull the hammer back slowly.

The hand is what you are seeing in the frame window. The hand bears against each ratchet in turn, causing the cylinder to rotate as the action cycles.

Cycling the action (dry firing) will help....as at does with any new firearm.

__________________
Ret. LE, FA Instr, S&W Armorer

Ok. The hand is flush with frame in the window. After 150 cycles I see no wear on ratchets or hand. Do any new 637 not have this issue? Someone at s&w let this pass.

Ok I just realized what you mean . The side of the hand needs to slip past the side of the ratchets....if the tolerance is tight you get what I have. Should I send it back?

Some of the new ones are "worse" than others. The resistance you are feeling at the end of the cycle will (should) lessen during the break in. If it's any consolation, what you are experiencing (full, early carry up) is much better than a situation where the cylinder doesn't carry up properly. You could contact Customer Service if it is deemed unacceptable, or you consider it a safety issue. (1-800-331-0852)


I had a similar situation with a model 442-1 I purchased recently. After a break in period, I was able to hand fit the ratchets to remove what I considered an unacceptable drag at the end of the DA cycle. When I first bought it, the gun carried up fine, and would have (did) passed inspection during assembly.

__________________
Ret. LE, FA Instr, S&W Armorer

Also thank you for taking the time to explain it to me.

Since I'm not an expert on it I don't know if it is unacceptable. If they are all similar to a certain extent than I am fine with it. If I send it in and all they do is say it passes their spec then that is a waste for everyone. Next time I am out I'll stop by a shop and test a few others I guess.
Each ratchet on my 637 must be the same dimension since all five hammer pulls feel he same.

I don't feel any of this in DA mode. DA mode is nice and smooth.

After your comment about the DA feel, I wouldn't worry any further about it. The contact between the hand and a slightly oversized ratchet you are experiencing will probably disappear during the break in period.

The feeling is worse in SA because in single action, the hand reaches a slightly higher point in the window, and consequently, will contact (pass) the ratchet a bit more after lock up is achieved.

Sounds like it's normal to me. Hope you enjoy the gun.

__________________
Ret. LE, FA Instr, S&W Armorer

Thank you again. Thank you very much.

It's normal. There will always be a shade of drag when the cylinder locks in place, then the hand has to "slip out from under" lifting the ratchet and slide by it on the right hand side. There will always be a bit of resistance it is more on new guns which are a shade tight. It will loosen up with wear.

Tight is better. It will break in and tighter means longer use time before it needs service from wear. As the hand and frame window wears, it will start carrying up short and need a new hand (after many thousands of rounds). Tighter is better.

Thank you again everyone!

The best way to resolve the tight/rough situation is to shoot the heck out of it. Not only will you smooth things out but you will become familiar and better with your firearm. An all around win-win.